Skin & Subcutaneous Tissue

Skin cancer screening: full-body skin exam in primary care

Clinical Overview and When to Suspect Skin Cancer in Primary Care

— Skin cancer is the most common malignancy in the US: ~1 in 5 Americans develop it by age 70

— Basal cell carcinoma (BCC) ~80%, squamous cell carcinoma (SCC) ~20% of keratinocyte cancers; melanoma is rarer but causes most skin cancer deaths

— Melanoma incidence rising, especially in adults >65 and in young women (trunk, lower extremities)

— I statement (insufficient evidence) for visual skin cancer screening by clinicians in asymptomatic adolescents and adults

— Does not recommend for or against routine full-body skin exam (FBSE) in average-risk patients

— Behavioral counseling on UV protection: B recommendation ages 6 months–24 years with fair skin; C for selective counseling in adults >24 with fair skin

— Personal history of melanoma, BCC, or SCC (highest risk factor)

— Family history of melanoma in ≥1 first-degree relative (especially CDKN2A families)

— Fitzpatrick I–II skin, red/blonde hair, blue eyes, freckling, blistering sunburns in childhood

— ≥50 common nevi or ≥5 atypical (dysplastic) nevi

— Immunosuppression: solid organ transplant (65–250× SCC risk), CLL, chronic HIV, long-term azathioprine or voriconazole

— Tanning bed use, occupational/recreational UV exposure, prior radiation, arsenic exposure

— Genodermatoses: xeroderma pigmentosum, basal cell nevus (Gorlin) syndrome, familial atypical multiple mole melanoma (FAMMM)

Scope of the problem

USPSTF stance (2023 update)

When to have a lower threshold for FBSE in primary care

Step 3 management: Even though USPSTF is "I," document a risk-based decision. In a high-risk patient (e.g., prior melanoma, transplant), schedule an annual FBSE or refer to dermatology — this is the defensible board answer.

Board pearl: A "concerned patient" presenting a changing mole is not screening — it is diagnostic evaluation, and a full skin exam plus biopsy of the lesion is always appropriate regardless of USPSTF screening grade.

Presentation Patterns and Key History

— "A mole that changed" — most sensitive layperson trigger for melanoma

— Non-healing sore >4–6 weeks, bleeds with minor trauma → BCC or SCC

— New pink/pearly papule on sun-exposed area in older adult

— Scaly, tender, hyperkeratotic plaque on scalp, ear, lip, dorsal hand → SCC or actinic keratosis (AK) progression

— Personal skin cancer history: type, site, date, treatment (Mohs vs excision), margins

— Family history: melanoma, pancreatic cancer (CDKN2A), multiple BCCs at young age (Gorlin)

— UV exposure: cumulative sun, ≥5 blistering sunburns before age 20 (doubles melanoma risk), indoor tanning before age 35 (75% ↑ melanoma)

— Immunosuppression: transplant date and regimen, HIV CD4, biologics

— Medications: voriconazole, hydrochlorothiazide (↑ SCC risk per FDA 2020 warning), photosensitizers

— Symptoms of the lesion: itch, pain, bleeding, change in size/color/shape, duration

— Asymmetry

— Border irregularity

— Color variegation (≥2 colors)

— Diameter >6 mm

— Evolution (the single most important feature)

Patient-initiated visit cues

Targeted history before FBSE

ABCDE rule for pigmented lesions

"Ugly duckling" sign: a nevus that looks different from the patient's other nevi — high specificity for melanoma, often more useful than ABCDE in patients with many nevi.

Key distinction: ABCDE misses nodular melanoma (often symmetric, uniform color, rapidly growing). Use the EFG addendum — Elevated, Firm, Growing >1 month — to catch nodular and amelanotic variants.

Board pearl: An older patient with a new "pyogenic granuloma–like" pink nodule that bleeds easily — think amelanotic melanoma until biopsy proves otherwise. Do not electrodessicate without histology.

Step 3 management: Document UV counseling (sunscreen SPF ≥30 broad-spectrum, reapply q2h, protective clothing, avoid tanning beds) at every well visit for fair-skinned patients ≤24 — this is the only B-grade intervention here.

Physical Exam Findings — Performing the Full-Body Skin Exam

— Private room, chaperone offered (and documented) for opposite-sex exam or sensitive areas

— Patient in gown, undergarments may remain; remove socks, nail polish, hairpieces

— Bright overhead light + handheld dermatoscope if trained

— Explain scope: scalp to soles, including scalp parting, behind ears, interdigital webs, nails, gluteal cleft, genitals, oral mucosa

— Scalp (part hair in sections), face, ears (helix, conchal bowl, postauricular), neck

— Anterior trunk, axillae, breasts/inframammary fold

— Upper extremities, dorsal and palmar hands, between fingers, nail plates

— Back (highest-yield site for melanoma in men), buttocks, gluteal cleft

— Lower extremities (highest-yield in women, especially calves), popliteal fossae

— Feet: dorsal, plantar (acral lentiginous melanoma site in darker skin types), interdigital, nails

— Genital and perianal skin (offer; document if deferred)

— BCC: pearly papule, telangiectasias, rolled borders, central ulceration ("rodent ulcer")

— SCC: hyperkeratotic, indurated, tender plaque or nodule; may arise from AK

— Melanoma: ABCDE + ugly duckling; check regional lymph nodes if suspected

— AK: gritty, sandpapery, erythematous macules on chronically sun-exposed skin — better felt than seen

Setup and consent

Systematic sequence (≈3–5 min)

Lesion-specific features

Dermoscopy (if trained): improves sensitivity for melanoma from ~70% to ~90%; pigment network, blue-white veil, atypical vessels are red flags.

Regional lymph node exam mandatory if a suspicious pigmented lesion is found — palpate cervical, axillary, epitrochlear, inguinal, popliteal nodes draining the area.

Board pearl: Acral lentiginous melanoma is the most common melanoma subtype in Black, Hispanic, and Asian patients. Always inspect palms, soles, and nail beds (Hutchinson sign = pigment extending onto proximal nail fold = melanoma).

CCS pearl: Order "skin biopsy, suspicious lesion" rather than cryotherapy when the diagnosis is uncertain — never destroy a pigmented lesion without histology.

Diagnostic Workup — Initial Evaluation of a Suspicious Lesion

— Total-body photography for high-risk patients (>50 nevi, atypical mole syndrome, prior melanoma) helps detect change at sequential visits

— Smartphone-based comparison or dedicated platforms acceptable in primary care; store in EMR with consent

— Polarized handheld device, 10× magnification

— Two-step algorithm: (1) melanocytic vs non-melanocytic, (2) benign vs suspicious

— Reduces unnecessary biopsies by ~50% in trained hands

— Full-thickness excisional biopsy with 1–3 mm margin is the gold standard for suspected melanoma — captures full Breslow depth

— Deep saucerization (scoop) shave acceptable if lesion is flat and excisional impractical; must reach subcutis

— Punch biopsy (4–6 mm) for large lesions where excisional not feasible — biopsy the darkest/thickest area

— Shave biopsy appropriate for suspected BCC/SCC but avoid for pigmented lesions (transects depth, compromises staging)

— Avoid incisional partial biopsies of small pigmented lesions when full excision is possible

— Do not cryotherapy or electrodessicate a pigmented or undiagnosed lesion

— Do not order LDH, CXR, or PET in a primary care patient with a suspicious mole pre-biopsy — staging follows histologic confirmation

No screening labs are indicated for asymptomatic skin cancer surveillance — no CBC, LDH, or imaging in average-risk patients.

Photographic documentation

Dermoscopy / Dermatoscopy

Biopsy technique selection — the key initial diagnostic step:

What not to do

Step 3 management: When in doubt → biopsy. A "watch and wait" plan for a lesion meeting any ABCDE criterion or ugly duckling is a wrong answer on the exam.

Board pearl: Subungual pigmented streak >3 mm wide, irregular, or with proximal nail fold extension (Hutchinson sign) → nail matrix biopsy by dermatology, not observation.

Key distinction: Screening asks "should I look at asymptomatic skin?" (USPSTF: I). Diagnosis asks "what is this lesion?" (always evaluate, often biopsy).

Diagnostic Workup — Confirmatory and Staging Studies

— Pathology report for melanoma must include: Breslow depth (mm), ulceration (yes/no), mitotic rate, margins, regression, microsatellites, lymphovascular invasion, perineural invasion, Clark level (less weighted now)

— Breslow depth is the single most important prognostic factor for localized melanoma

— Tis: in situ

— T1a: ≤1.0 mm, no ulceration (T1a now <0.8 mm without ulceration)

— T1b: 0.8–1.0 mm OR <0.8 mm with ulceration

— T2: >1.0–2.0 mm; T3: >2.0–4.0 mm; T4: >4.0 mm

— Suffix a = no ulceration, b = ulceration

— Offer for T1b–T2 (≥0.8 mm or ulcerated)

— Recommend for T2b and higher

— Performed at time of wide local excision by surgical oncology

— Stage 0–II asymptomatic: no routine imaging (NCCN)

— Stage III/IV or symptomatic: CT chest/abdomen/pelvis ± brain MRI, or PET/CT

— LDH: prognostic in stage IV (M1c, M1d), not screening

— BRAF V600 mutation testing for stage III/IV — drives targeted therapy (dabrafenib + trametinib, encorafenib + binimetinib)

— Not routine for stage I/II

— Histology confirms subtype: nodular, superficial, morpheaform (high-risk) BCC; well- vs poorly-differentiated SCC

— High-risk SCC features (≥2 cm, depth >6 mm, perineural invasion, immunosuppressed host, ear/lip site) → imaging for nodal disease, consider SLNB

Histopathology is definitive

AJCC 8th edition T staging (melanoma)

Sentinel lymph node biopsy (SLNB)

Imaging — only when indicated

Molecular testing

For BCC/SCC

CCS pearl: After a primary care biopsy returns "invasive melanoma," the correct CCS sequence: refer to dermatology or surgical oncology for wide local excision ± SLNB → counsel patient → schedule oncology if stage III+. Do not order PET yourself for stage I.

Board pearl: Breslow ≥0.8 mm or ulceration = SLNB discussion. Memorize 0.8 mm as the threshold.

Risk Stratification and First-Line Management Logic

— No personal/family history, Fitzpatrick III–VI, no immunosuppression

— No routine FBSE recommended (USPSTF I); focus on UV counseling and patient self-exam education

— Address concerning lesions when raised by patient

— Fair skin + multiple sunburns, ≥50 nevi, occupational UV, family history of non-melanoma skin cancer

— Consider opportunistic FBSE during periodic health exams (shared decision-making)

— Teach monthly self-skin exam with partner/mirror for posterior sites

— Personal history of melanoma: lifetime risk of second primary ~3–5%, highest in first 2 years

— Personal history of BCC/SCC: 35–50% 5-year recurrence or new keratinocyte cancer

— Solid organ transplant recipient (SOTR)

— ≥5 atypical nevi or familial atypical multiple mole melanoma (FAMMM)

— Genodermatoses (xeroderma pigmentosum → start in infancy)

— Prior therapeutic radiation to skin

— Stage 0 melanoma: skin exam q6–12 months for life

— Stage I–IIA: q6–12 months × 5 years, then annually

— Stage IIB–IV: q3–6 months × 2 years, then q3–12 months

— SOTR: baseline derm referral within 1–2 years of transplant; then annual FBSE, more often if cancer develops

Stratify every primary care patient into a screening tier

Average risk

Increased risk

High risk → annual or more frequent FBSE; consider dermatology co-management

Suggested intervals (NCCN/AAD expert opinion, not USPSTF)

Step 3 management: Identify the risk tier first, then choose interval. A transplant patient on tacrolimus with a prior SCC needs derm follow-up every 3–6 months, not annual.

Board pearl: Switching SOTR from a calcineurin inhibitor to sirolimus (mTOR inhibitor) reduces subsequent SCC risk — coordinate with transplant nephrology.

Key distinction: Screening interval is risk-driven, not age-driven. There is no upper age cutoff if life expectancy supports treatment.

Counseling and Behavioral "Pharmacotherapy" — Primary Prevention

— B recommendation: counsel fair-skinned patients ages 6 months–24 years to minimize UV exposure

— C recommendation: selectively counsel adults >24 with fair skin based on individual risk

— I statement: counseling all adults regardless of skin type; skin self-exam

— Slip on protective clothing (long sleeves, UPF-rated)

— Slop on sunscreen: broad-spectrum, SPF ≥30, reapply every 2 hours and after swimming/sweating

— Slap on a wide-brimmed hat

— Slide on UV-blocking sunglasses

— Shade — avoid sun 10 AM–4 PM; avoid tanning beds entirely

— Mineral (zinc oxide, titanium dioxide) preferred for infants >6 months, sensitive skin, pregnancy

— Chemical sunscreens (avobenzone, octinoxate) effective but some absorbed systemically — FDA evaluating

— Apply ~1 oz (shot glass) for full-body coverage in adults

— Sun avoidance does not require deficiency; recommend dietary intake or supplementation (600–800 IU/day) rather than UV exposure

— Nicotinamide (vitamin B3) 500 mg BID: ONTRAC trial — 23% reduction in new keratinocyte cancers in patients with ≥2 prior NMSC; safe, low cost

— Topical 5-FU field therapy for actinic keratoses; reduces SCC by ~75% over 4 years (VAKCC trial)

— Acitretin for transplant recipients with multiple SCCs (teratogenic — not for women of reproductive potential)

USPSTF behavioral counseling (2018, reaffirmed 2023)

Counseling content (the "5 S's")

Sunscreen specifics

Vitamin D consideration

Chemoprevention (selected high-risk patients, dermatology-directed)

Board pearl: Nicotinamide ≠ niacin — does not cause flushing, hepatotoxicity, or lipid changes. Recommendable in primary care for any patient with ≥2 prior keratinocyte cancers.

Step 3 management: At an adolescent well visit for a red-haired, freckled 16-year-old, the highest-yield single intervention is structured UV-protection counseling — this is the only B-grade preventive service for this topic.

Procedures in Primary Care — Biopsy Techniques and Referrals

— Recognize and biopsy non-pigmented suspicious lesions (BCC, SCC, AK)

— Perform shave or punch biopsy with proper technique

— Cryotherapy for diagnosed AK or seborrheic keratosis (not undiagnosed pigmented lesions)

— Refer pigmented suspicious lesions to dermatology if uncomfortable with excisional biopsy

— Indications: raised non-pigmented lesion, suspected BCC/SCC

— Technique: local 1% lidocaine with epi (avoid epi on digits if peripheral disease), flexible blade, depth to mid-dermis or subcutis

— Hemostasis: aluminum chloride, electrocautery

— Limitation: may transect deep lesions — do not use for suspected melanoma

— 3–6 mm trephine; rotate to subcutis; lift with skin hook (avoid forceps crush)

— Single suture closure for ≥4 mm

— Best for inflammatory plaques, larger pigmented lesions when excisional not feasible

— Narrow margin 1–3 mm of normal skin, oriented along skin tension lines or lymphatic drainage

— Down to subcutaneous fat

— Refer to dermatology/surgery if anatomically complex (face, ear, digit, genital)

— BCC/SCC low-risk: standard excision with 4–6 mm margins

— High-risk or cosmetic sites: Mohs micrographic surgery (face, ears, digits, recurrent tumors)

— Melanoma WLE margins: in situ 0.5–1 cm; ≤1 mm Breslow → 1 cm; 1.01–2 mm → 1–2 cm; >2 mm → 2 cm

— Superficial BCC/in situ SCC: topical 5-FU, imiquimod, or photodynamic therapy as alternatives

What primary care can and should do

Shave biopsy (deep saucerization)

Punch biopsy

Excisional biopsy for suspected melanoma

Definitive treatment after diagnosis

CCS pearl: After punch biopsy returns BCC on the nasal tip in a 70-year-old, the next order is referral to Mohs surgery, not standard excision — cosmetically sensitive and high-recurrence site.

Board pearl: Never cryotherapy a pigmented lesion. Melanomas have been "treated" this way and missed — exam favorite.

Special Populations — Elderly and Renal/Hepatic Impairment

— Highest absolute incidence of all skin cancers; 80% of melanoma deaths occur in men >50

— Nodular and lentigo maligna melanomas more common — different exam pattern (often face, scalp in balding men)

— Lower screening evidence in age >65 (USPSTF noted possible benefit signal but insufficient data)

— Use ePrognosis or clinical judgment: if life expectancy <5–10 years and patient is asymptomatic average risk, intensive screening yields little benefit

— A 90-year-old with dementia and an asymptomatic 4-mm pigmented macule: shared decision, often observe

— A robust 80-year-old with prior melanoma: continue surveillance — they will benefit from early-stage detection

— Hydrochlorothiazide: FDA labeling change 2020 — increased risk of cutaneous SCC and lip SCC with cumulative dose; consider alternative in high-risk patients

— Voriconazole long-term: aggressive SCCs — switch antifungal in transplant patients when possible

— Photosensitizers: amiodarone, tetracyclines, thiazides, sulfonamides — counsel sun protection

— Dialysis and CKD patients have ~2–3× increased keratinocyte cancer risk, particularly post–kidney transplant

— Annual FBSE in CKD G5/dialysis with prior skin cancer

— Limits use of acitretin (hepatotoxic), methotrexate; doses of local lidocaine are still safe at standard volumes

— Childbearing-age women with cirrhosis: avoid acitretin (3-year teratogenic window)

Older adults (≥65)

Life expectancy framing

Polypharmacy considerations

Renal impairment

Hepatic impairment

Step 3 management: A 78-year-old on chronic HCTZ presents with a new scaly plaque on the lower lip → biopsy (likely SCC), substitute HCTZ with chlorthalidone or amlodipine, and counsel sun protection.

Board pearl: In an elderly patient with melanoma, lentigo maligna on the cheek may evolve over decades — depth is often shallow but local recurrence rates after standard excision are high; Mohs or staged excision preferred.

Key distinction: Screening intensity in the elderly is governed by life expectancy and risk, not chronologic age.

Special Populations — Pregnancy, Pediatrics, and Skin of Color

— Melanoma is among the most common cancers diagnosed in pregnancy

— Pregnancy does not worsen melanoma prognosis stage-for-stage (older teaching disproven)

— Biopsy of suspicious lesions is safe in any trimester under local lidocaine (Category B equivalent)

— Wide local excision can proceed; SLNB can be performed (technetium-99 sulfur colloid acceptable; avoid isosulfan blue dye in pregnancy)

— Imaging: prefer ultrasound and MRI without gadolinium; defer PET/CT if possible

— Mild darkening of existing nevi may occur, but a truly evolving lesion warrants biopsy — do not attribute change to pregnancy

— Pediatric melanoma is rare but rising; ABCDE less sensitive

— Modified ABCD for kids: Amelanotic, Bleeding/Bump, Color uniform, De novo/Diameter — refer suspicious lesions

— Spitz nevi mimic melanoma — biopsy and dermatopathology review essential

— Counsel parents: ≥5 blistering sunburns in childhood doubles lifetime melanoma risk; tanning beds banned for minors in many states

— Lower overall incidence but higher melanoma mortality due to later diagnosis

— Acral lentiginous melanoma predominates: palms, soles, subungual

— SCC arises in non–sun-exposed sites: chronic scars, burns, ulcers, HPV-related anogenital sites

— Patient education and clinician training to examine palms, soles, oral mucosa, perianal area

Pregnancy

Counseling pregnant patients on changing nevi

Pediatrics

Xeroderma pigmentosum: start FBSE in infancy, strict UV avoidance, dermatology q3 months

Skin of color (Fitzpatrick IV–VI)

CCS pearl: A 55-year-old Black patient with a 2-month new pigmented streak on the great toe nail bed → nail matrix biopsy referral, not reassurance.

Board pearl: Bob Marley died of acral lentiginous melanoma of the toe — a classic exam stem for melanoma in darker skin types. Always inspect feet.

Step 3 management: In pregnancy, never delay biopsy of a suspicious lesion until postpartum — that is a wrong answer.

Complications and Adverse Outcomes

— Melanoma: progression from in situ (curable >99%) to thick (>4 mm, 5-yr survival ~50%) over months

— Locoregional metastasis: in-transit, satellite, regional nodes

— Distant metastasis: lung, liver, brain, bone, GI; LDH rises in M1c/M1d

— SCC metastasis: regional nodes in 2–5% overall, up to 20–40% in high-risk sites (lip, ear, immunosuppressed)

— BCC metastasis is exceptionally rare (<0.1%) but local destruction can be severe (orbital invasion, skull base)

— Overdiagnosis: detection of indolent melanoma in situ that may never progress — drives the USPSTF "I" stance

— Overtreatment: unnecessary excisions, scarring, psychological burden

— Estimated 20–30 benign lesions biopsied per melanoma detected in primary care

— Bleeding (especially on anticoagulants — generally do not stop warfarin/DOACs for skin biopsy; risk of bleeding < risk of thromboembolism)

— Infection (~1–2%)

— Scar, keloid, hypopigmentation in darker skin types

— Nerve injury on face (temporal branch of facial nerve, spinal accessory in posterior triangle)

— Mohs/WLE: cosmetic deformity, lymphedema after groin/axillary dissection

— Radiation: chronic radiation dermatitis, secondary cancers

— Systemic therapy for advanced melanoma: immune-related adverse events from PD-1 inhibitors (colitis, hepatitis, pneumonitis, hypophysitis, thyroiditis)

— BRAF/MEK inhibitors: pyrexia, photosensitivity, secondary cutaneous SCCs (esp. vemurafenib)

— Anxiety surrounding nevus surveillance; "scanxiety" before dermatology visits

— Body image after facial Mohs surgery

Of missed/delayed diagnosis

Of screening itself

Procedural complications of biopsy/excision

Of definitive therapy

Psychosocial

Board pearl: A patient on pembrolizumab for metastatic melanoma presents with watery diarrhea — think immune-related colitis; hold the drug, start high-dose prednisone, infliximab if refractory.

Step 3 management: Continue anticoagulation through skin biopsy; document the shared decision.

When to Escalate Care — Referral and Inpatient Triage

— Multiple atypical nevi requiring full-body photography and serial surveillance

— Suspected melanoma in cosmetically sensitive site (face, ear, digit, genital)

— Recurrent or high-risk BCC/SCC

— Solid organ transplant recipient establishing skin care

— Diagnostic uncertainty about a pigmented lesion in primary care

— Rapidly growing nodular lesion suspicious for nodular or amelanotic melanoma

— High-grade SCC with perineural symptoms (numbness, paresthesia) — concern for invasion

— Subungual pigmented lesion with Hutchinson sign

— Confirmed invasive melanoma for wide local excision ± SLNB

— High-risk SCC requiring nodal staging

— Locally advanced BCC for combined approach

— Stage III–IV melanoma (adjuvant nivolumab/pembrolizumab or dabrafenib/trametinib for BRAF+)

— Advanced cutaneous SCC (cemiplimab) or BCC (vismodegib, sonidegib)

— Adjuvant therapy for high-risk SCC with perineural invasion, positive margins not amenable to re-excision

— Definitive therapy for inoperable lesions

— Bleeding, fungating tumor uncontrolled outpatient

— Sepsis from infected ulcerated tumor

— Symptomatic brain metastases (seizure, focal deficit) → ED, neurosurgery, oncology

— Severe immune-related adverse events from checkpoint inhibitor (grade 3–4): admit for IV steroids ± immunosuppression

— ≥3 melanomas in patient, or melanoma + pancreatic cancer in family → CDKN2A testing

— Multiple BCCs before age 30 or jaw cysts → Gorlin syndrome (PTCH1)

Refer to dermatology (outpatient, routine)

Refer urgently (within 1–2 weeks)

Refer to surgical oncology

Refer to medical oncology

Refer to radiation oncology

Inpatient triage (rare for skin cancer itself)

Genetic counseling referral

CCS pearl: New focal neurologic deficit in a melanoma survivor → order MRI brain with contrast stat; admit if metastasis confirmed for neurosurgery/radiation oncology consult.

Step 3 management: Don't keep a confirmed invasive melanoma in primary care — definitive surgery within ~4–6 weeks of diagnosis is the standard.

Key Differentials — Pigmented and Other Skin Lesions

— Seborrheic keratosis: "stuck-on," waxy, warty surface, horn cysts on dermoscopy; common in older adults — treat with cryotherapy if symptomatic

— Solar lentigo: uniform tan-brown macule on sun-exposed skin; flat, no atypia

— Dermatofibroma: firm, hyperpigmented papule, dimple sign when squeezed laterally; lower legs in women

— Blue nevus: dome-shaped, deeply pigmented blue-black nodule; stable since adolescence

— Congenital nevus: present at birth, may darken/grow proportionally; giant >20 cm carries lifetime melanoma risk ~5%

— Spitz nevus: pink-red dome in children; must distinguish from spitzoid melanoma — biopsy

— Actinic keratosis: gritty erythematous macule, sun-damaged skin; precursor to SCC (≤1% per year per lesion); treat with cryotherapy, 5-FU, imiquimod, PDT, tirbanibulin

— Keratoacanthoma: rapidly growing dome with central keratin plug; often treated as well-differentiated SCC — excise

— Bowen disease (SCC in situ): scaly erythematous patch; topical 5-FU or excision

— Pyogenic granuloma: friable bleeding red papule, often post-trauma or pregnancy ("granuloma gravidarum") — must rule out amelanotic melanoma if atypical

— Superficial spreading (~70%): radial growth phase, ABCDE classic

— Nodular (~15%): rapid vertical growth, EFG, often misses ABCDE

— Lentigo maligna: face, elderly, slow horizontal spread

— Acral lentiginous: palms, soles, nails; not UV-related; Fitzpatrick IV–VI predominant

Benign mimics of melanoma

Pigmented BCC — can mimic melanoma; dermoscopy shows leaf-like structures, blue-gray ovoid nests

Other lesions to know

Within melanoma family

Board pearl: Dimple sign + lower leg + middle-aged woman = dermatofibroma, not melanoma. Reassure, no biopsy needed unless changing.

Key distinction: Seborrheic keratosis = "stuck-on, waxy, horn cysts." Melanoma = ABCDE + ugly duckling + evolution. When you cannot tell — biopsy.

Key Differentials — Non-Cutaneous and Systemic Mimics

— Cherry angioma: bright red dome, common after age 30, benign

— Angiokeratoma: dark vascular papule on scrotum/vulva (Fordyce) or generalized (Fabry disease — ask about pain, anhidrosis, renal/cardiac)

— Kaposi sarcoma: violaceous patches/plaques/nodules; consider in HIV/AIDS, elderly Mediterranean men, transplant patients — biopsy, check HHV-8

— Cutaneous T-cell lymphoma (mycosis fungoides): scaly patches/plaques resistant to topical steroids in non-sun-exposed "bathing trunk" distribution — multiple biopsies often needed

— Chronic cutaneous leishmaniasis: ulcer with raised border in returning traveler from Middle East/South America

— Cutaneous tuberculosis (lupus vulgaris): red-brown "apple jelly" plaque

— Deep fungal infections (sporotrichosis, blastomycosis): verrucous plaques mimicking SCC — biopsy with cultures, special stains

— Atypical mycobacteria: M. marinum after aquatic exposure

— Breast (most common in women — chest wall nodules), lung, colon, ovarian, renal

— Sister Mary Joseph nodule: umbilical metastasis from GI/GU malignancy

— A new firm nodule in a known cancer survivor → biopsy

— Acanthosis nigricans (malignant type): sudden, extensive — gastric adenocarcinoma

— Tripe palms, sign of Leser-Trélat (sudden eruption of seborrheic keratoses): GI malignancy

— Necrolytic migratory erythema: glucagonoma

— Dermatomyositis in adults: search for malignancy

— BRAF inhibitor-induced keratoacanthomas and SCCs

— Hydroxyurea-induced leg ulcers and SCCs

Vascular and inflammatory lesions mimicking skin cancer

Infectious lesions

Metastatic disease to skin

Paraneoplastic dermatoses

Drug-induced lesions

Board pearl: A 45-year-old with a non-healing leg ulcer at the site of a chronic burn → biopsy the edge for Marjolin ulcer (SCC arising in chronic wound), aggressive variant.

Step 3 management: A new firm scalp nodule in a 60-year-old smoker — punch biopsy and consider cutaneous metastasis from lung primary; order CXR/CT.

Long-Term Plan, Secondary Prevention, and Survivorship

— BCC: FBSE every 6–12 months × 5 years, then annually for life (35% develop a new BCC within 5 years)

— SCC low-risk: every 6–12 months × 2 years, then annually; high-risk SCC: every 3–6 months × 2 years

— Melanoma in situ (stage 0): every 6–12 months for life; teach monthly self-exam

— Stage I–IIA: every 6–12 months × 5 years, then annually; consider total-body photography

— Stage IIB–IV: every 3–6 months × 2 years, then q3–12 months × 3 years, then annual; imaging per oncology

— Lifelong daily broad-spectrum SPF ≥30

— Nicotinamide 500 mg PO BID for patients with ≥2 prior keratinocyte cancers

— Treat field cancerization with topical 5-FU, imiquimod, or PDT (dermatology)

— Switch SOTR to mTOR inhibitor (sirolimus/everolimus) when feasible

— Stop tanning bed use (counseling, motivational interviewing)

— Replace photosensitizing antihypertensives (HCTZ) in high-risk patients

— Monthly head-to-toe self-exam, ideally with partner for back and scalp

— Use mirror, smartphone photos for stable nevi

— Report any new, changing, bleeding, or itching lesion within 1–2 weeks

— First-degree relatives of melanoma patients have 2× risk → encourage annual dermatology exam, especially if multiple affected relatives → genetic counseling for CDKN2A

— HPV vaccination reduces anogenital SCC risk

— Smoking cessation (oral SCC risk)

— Encourage skin checks during diabetic foot exams in primary care — opportunistic detection

After any skin cancer diagnosis — establish a survivorship plan

Surveillance schedule

Secondary prevention pearls

Patient self-exam education

Family screening

Vaccinations and general health

Board pearl: Highest 5-year risk of a second primary melanoma is in the first 2 years after the first — this is when surveillance must be most intensive.

Step 3 management: Write the patient a written survivorship care plan with diagnosis, treatment, follow-up schedule, late-effect warnings, and primary care responsibilities — required for quality measures (Commission on Cancer).

Follow-Up, Monitoring Parameters, and Counseling

— Date and findings of last FBSE

— Lesion log: location, size, dermoscopic features, changes from baseline photos

— New biopsies and pathology results

— Sun protection adherence and tanning bed cessation

— UV exposure history since last visit

— Self-exam practice (frequency, technique)

— Symptoms suggesting recurrence/metastasis: new lumps, lymphadenopathy, neurologic symptoms, unexplained weight loss, persistent cough, abdominal pain

— Inspect prior excision site for in-transit/satellite recurrence

— Palpate regional nodal basins (cervical, axillary, inguinal, popliteal)

— Full skin exam for new primaries (~3–5% lifetime risk of second melanoma)

— Stage 0–IIA: no routine labs/imaging; symptom-directed only

— Stage IIB–III: oncology may order surveillance CT chest/abdomen/pelvis every 6–12 months × 3–5 years and brain MRI annually × 3 years

— Stage IV / on systemic therapy: per oncology; primary care monitors for immune-related AEs (TSH q4–6 weeks on PD-1, transaminases, glucose, cortisol if symptomatic)

— Mental health: anxiety, depression after diagnosis — screen with PHQ-2/9

— Fertility considerations before adjuvant therapy in young patients

— Cost: high copays for checkpoint inhibitors; refer to patient assistance programs

— Driving and occupational UV exposure (truckers, farmers, lifeguards) — protective film for car windows

— Inactivated vaccines safe with checkpoint inhibitors; avoid live vaccines during/after immunotherapy until clearance from oncology

— Annual influenza and updated COVID vaccines recommended

At every follow-up FBSE visit, document

Targeted exam for known melanoma patients

Monitoring parameters by stage

Counseling topics

Vaccination/immunization in survivors

CCS pearl: For a patient on pembrolizumab — order TSH every 4–6 weeks during therapy; new hypothyroidism is common (~10%) and easily missed.

Step 3 management: Coordinate care via a shared dashboard between primary care, dermatology, and oncology. Primary care owns lifestyle, secondary prevention, and surveillance reminders.

Ethical, Legal, and Patient Safety Considerations

— Document verbal consent for full-body inspection, including genital and gluteal areas

— Offer a chaperone for all sensitive exams regardless of clinician/patient gender; document offer and acceptance/refusal

— Patient may decline certain regions — respect, document, and counsel about implications (e.g., declining genital exam may miss anogenital SCC, especially in HIV/HPV-positive patients)

— Discuss alternatives, risks (bleeding, infection, scar, nerve injury), benefits, and what happens if results are positive (further surgery)

— In patients with limited capacity or language barriers: certified medical interpreter required; family/ad hoc interpreters are inadequate for procedural consent

— Cancer diagnoses must be reported to state cancer registries (handled by pathology in most states)

— Suspected abuse: unusual burns, unexplained injuries in elderly or pediatric skin exams → mandated reporter duty

— Biopsy result follow-up is the highest medicolegal risk in primary care dermatology

— Establish a closed-loop system: track every biopsy specimen, document path receipt, contact patient with results within 1–2 weeks, document attempts (calls, certified letter)

— A missed melanoma diagnosis due to lost biopsy result is a leading malpractice claim — implement a tickler/EMR alert

— Disclose to patients that screening can find indolent lesions; shared decision-making improves informed choice

— Avoid "more is better" thinking in low-risk patients

— Patients with skin of color and lower SES are diagnosed at later stages with higher mortality — proactively educate, examine acral/oral sites

— Insurance coverage of dermatology referrals varies; offer Medicaid-friendly options

— Sensitive findings (e.g., HPV-related anogenital lesions) require careful documentation and disclosure

Informed consent for FBSE

Informed consent for biopsy

Mandatory reporting and disclosure

Transitions of care risk

Overdiagnosis ethics

Equity considerations

Confidentiality

Board pearl: The single highest-yield patient safety intervention in skin cancer care is a closed-loop biopsy result tracking system with documented patient notification.

Step 3 management: Patient missed two appointments after a biopsy returned "melanoma in situ" — send certified letter, attempt phone contact, document all efforts; consider involving care coordination.

High-Yield Associations and Rapid-Fire Clinical Facts

— UVB → "burns" and direct DNA damage (pyrimidine dimers); UVA → "ages" and oxidative damage; both cause skin cancer

— Tanning bed use before age 35 → 75% ↑ melanoma risk

— ≥5 sunburns before age 20 → doubles lifetime melanoma risk

— CDKN2A (p16): familial melanoma + pancreatic cancer

— BRAF V600E: 40–50% of melanomas; targets dabrafenib/trametinib

— PTCH1: Gorlin (basal cell nevus) syndrome — multiple BCCs, jaw cysts, palmar pits, medulloblastoma, calcified falx cerebri

— TP53 (Li-Fraumeni): sarcomas, breast, brain, adrenal — not classically skin

— Xeroderma pigmentosum: nucleotide excision repair defect; thousands-fold ↑ skin cancer

— Hydrochlorothiazide → SCC (lip, skin)

— Voriconazole long-term → aggressive SCC in transplant patients

— Vemurafenib → secondary keratoacanthomas/SCCs

— Hedgehog inhibitors (vismodegib, sonidegib) → advanced/metastatic BCC

— Melanoma 5-yr survival: stage IA 99%, stage IIC ~70%, stage IIIC ~60%, stage IV ~30% (improving with immunotherapy)

— Breslow threshold for SLNB discussion: 0.8 mm or ulceration

— WLE margins: in situ 0.5–1 cm, ≤1 mm 1 cm, 1–2 mm 1–2 cm, >2 mm 2 cm

— Marjolin ulcer = SCC in chronic burn/scar

— Sister Mary Joseph nodule = umbilical metastasis (GI/GU)

— Leser-Trélat sign = sudden seborrheic keratoses + visceral malignancy

— Hutchinson sign = pigment on proximal nail fold = subungual melanoma

— Nicotinamide 500 mg BID → 23% ↓ keratinocyte cancers (ONTRAC)

— Beta-carotene/vitamin E supplements do not prevent skin cancer

UV and risk

Genetics

Drugs

Numbers to know

Classic associations

Vitamin/nutraceutical

Board pearl: USPSTF gives B to UV counseling in fair-skinned patients 6 months–24 years; I to clinician visual skin cancer screening. Know these grades.

Step 3 management: Don't memorize chemotherapy regimens; do know SLNB at 0.8 mm, nicotinamide for chemoprevention, and Mohs for face/ear/digit.

Board Question Stem Patterns

— Stem: A 45-year-old asymptomatic average-risk adult asks about a full-body skin exam. What do you recommend?

— Answer: Counsel UV protection; discuss that USPSTF found insufficient evidence to recommend for or against routine FBSE — shared decision-making.

— Trap: Choosing "annual dermatology referral for all adults" — overuse.

— Stem: A 38-year-old notes a back mole has darkened and grown over 3 months; asymmetric, 8 mm, two colors.

— Answer: Excisional biopsy with 1–3 mm margins, full thickness to subcutis.

— Traps: Shave biopsy (transects depth), cryotherapy, observation, dermoscopy alone.

— Stem: A 60-year-old Black patient with a 4-mm-wide pigmented streak on the thumb nail and brown pigment extending onto the proximal nail fold.

— Answer: Refer for nail matrix biopsy; concern for acral lentiginous melanoma (Hutchinson sign).

— Stem: A 55-year-old kidney transplant recipient on tacrolimus 8 years out develops multiple scaly plaques on dorsal hands.

— Answer: Refer to dermatology for biopsy/treatment of likely SCCs; discuss switching to sirolimus; intensive surveillance every 3–6 months; consider acitretin chemoprevention.

— Stem: Biopsy returns invasive melanoma but patient missed two follow-up calls.

— Answer: Document calls, send certified letter, attempt all contact means — closed-loop tracking.

— Stem: Red-haired 14-year-old with freckles for well visit.

— Answer: Counsel on UV protection (USPSTF B recommendation); discourage tanning beds.

— Stem: 72-year-old on long-term HCTZ presents with new lip lesion.

— Answer: Biopsy; consider switching HCTZ to alternative.

— Stem: 68-year-old with 3 prior BCCs in past 4 years.

— Answer: Nicotinamide 500 mg PO BID.

Pattern 1 — The USPSTF screening question

Pattern 2 — The changing mole

Pattern 3 — The subungual streak

Pattern 4 — Transplant patient

Pattern 5 — Post-biopsy follow-up failure

Pattern 6 — UV counseling in adolescent

Pattern 7 — Drug-related SCC

Pattern 8 — Chemoprevention

Board pearl: Stems including "Breslow 0.9 mm" or "0.8 mm with ulceration" want you to answer SLNB discussion at WLE.

CCS pearl: Always order biopsy before destruction; always close the loop on results.

One-Line Recap

In primary care, skin cancer "screening" via full-body skin exam is risk-stratified — USPSTF rates clinician visual screening as "I" in average-risk adults, but high-risk patients (prior skin cancer, transplant, atypical mole syndrome, fair skin with heavy UV exposure) merit periodic FBSE, while every patient deserves UV-protection counseling and prompt biopsy of any suspicious or evolving lesion.

— USPSTF grades to memorize: clinician FBSE in asymptomatic adults = I (insufficient evidence); UV-protection counseling for fair-skinned patients 6 months–24 years = B; selective counseling adults >24 = C; skin self-exam = I.

— Diagnostic rule: any pigmented lesion meeting ABCDE, ugly duckling, or EFG criteria → full-thickness excisional biopsy 1–3 mm margins. Never cryotherapy or shave a suspected melanoma. Subungual pigment with Hutchinson sign → nail matrix biopsy.

— Risk-tiered surveillance: average risk = counseling only; high risk (prior melanoma, transplant, FAMMM, XP) = annual or more frequent FBSE ± dermatology co-management; SOTR consider switch to sirolimus; ≥2 prior keratinocyte cancers consider nicotinamide 500 mg BID chemoprevention.

— Critical Step 3 systems issue: implement a closed-loop biopsy result tracking system; missed melanoma diagnosis from lost biopsy results is a top malpractice risk and patient safety failure — every biopsy must have documented result delivery to the patient within 1–2 weeks, with escalating contact attempts (call, letter, certified mail) if needed.

High-yield recap bullets

Board pearl: When in doubt, biopsy — and close the loop on the result.