Skin & Subcutaneous Tissue

Dysplastic nevi: surveillance and biopsy

Clinical Overview and When to Suspect Dysplastic Nevi

— Present in ~2–8% of fair-skinned US adults; more common in patients with extensive sun exposure and family history of melanoma.

— Atypical mole syndrome (formerly dysplastic nevus syndrome / FAMMM): ≥100 nevi, ≥1 atypical nevus ≥8 mm, and ≥1 nevus with histologic atypia. Confers markedly elevated melanoma risk, especially with CDKN2A mutations.

— Patient reports a changing mole ("ugly duckling sign" — a lesion that looks different from the patient's other nevi).

— New nevus appearing after age 40.

— Symptomatic lesion: itching, bleeding, ulceration, or persistent tenderness.

— Personal history of melanoma (10× risk of second primary) or ≥1 first-degree relative with melanoma.

— Fitzpatrick I–II skin, red/blond hair, blue eyes, freckling.

— Total nevus count >50.

— History of blistering sunburns, tanning bed use before age 35 (75% increased melanoma risk).

— Immunosuppression (transplant, chronic HIV).

— Germline mutations: CDKN2A, CDK4, BAP1, MC1R variants.

Board pearl: A solitary dysplastic nevus in a low-risk patient is not by itself a melanoma precursor warranting prophylactic excision — surveillance and patient education are first-line. Reflexive removal of every atypical-appearing mole is a wrong-answer trap on Step 3.

Definition: Dysplastic (atypical) nevi are acquired melanocytic lesions with clinical and histologic features intermediate between common nevi and melanoma — irregular borders, variable pigmentation, often >5 mm, with architectural and cytologic atypia on pathology.

Epidemiology and risk context:

Why Step 3 cares: Family medicine and preventive medicine boards emphasize risk stratification, surveillance cadence, biopsy decisions, and patient counseling rather than diagnosis alone. You will be asked when to watch, when to photograph, when to biopsy, and when to refer.

When to suspect a problematic nevus:

Risk factors driving surveillance intensity:

Presentation Patterns and Key History

— 30–55-year-old fair-skinned patient presents for routine skin exam or notices a "changing mole." May report a relative diagnosed with melanoma, prompting evaluation.

— Lesions favor sun-exposed trunk and extremities but can occur on scalp, buttocks, breasts, and other covered areas — examine the entire skin surface, including scalp, soles, web spaces, genitalia, and nails.

— Lesion-specific: onset, rate of change, symptoms (itch, bleed, pain), prior biopsies, prior treatments (cryotherapy or shave that may distort findings).

— Personal history: prior melanoma or non-melanoma skin cancer, organ transplant, chemotherapy, radiation, immunosuppressants, photosensitizing meds (voriconazole, hydrochlorothiazide).

— Family history: melanoma, pancreatic cancer (CDKN2A), mesothelioma/uveal melanoma (BAP1).

— Sun exposure: occupational/outdoor work, latitude of residence, lifetime sunburns, tanning bed use (quantify sessions before age 25).

— Social: smoking (poor wound healing if biopsy), occupation, ability to perform self-skin exams.

— Asymmetry, Border irregularity, Color variation, Diameter >6 mm, Evolution.

— "Ugly duckling": one mole that does not resemble the patient's overall nevus pattern — most sensitive single sign in patients with many nevi.

Step 3 management: In a patient with ≥5 atypical nevi or familial atypical multiple mole melanoma syndrome, baseline total-body photography ± dermoscopy with digital mole mapping is the standard of care to detect new or changing lesions over time — order this at the index visit rather than serial random biopsies.

Typical clinical scenario:

History elements to capture (the "Step 3 skin history"):

Patient-reported red flags (ABCDE refresher applied to surveillance):

Counseling history: ask about prior sunscreen use, hat/UPF clothing habits, willingness to perform monthly self-skin exams with partner assistance for hard-to-see areas, and access to dermatology.

Physical Exam Findings and Dermoscopic Assessment

— Patient fully undressed in gown, good overhead and handheld lighting; examine scalp (part hair), retroauricular folds, oral mucosa, palms, soles, interdigital webs, nails (look for longitudinal melanonychia >3 mm or Hutchinson sign), perineum, and gluteal cleft.

— Document lesions with body-map diagram; measure with ruler; photograph suspicious lesions with adjacent scale.

— Size typically 5–15 mm.

— "Fried-egg" appearance: central raised papular component with surrounding flat macular pigmented rim.

— Asymmetric outline, fuzzy/indistinct borders.

— Variegated tan-brown-pink color with possible darker focal areas.

— Usually multiple and scattered, not solitary.

— Reticular, globular, or homogeneous patterns are usually benign.

— Red-flag dermoscopic features suggesting melanoma over dysplastic nevus: atypical pigment network, irregular streaks/pseudopods, blue-white veil, regression structures (white scar-like areas), polymorphous vessels, asymmetry of structure and color in two perpendicular axes.

— Use the "two-step algorithm": confirm melanocytic origin, then apply pattern analysis or a 7-point checklist.

— Within an individual's nevi, look for the lesion that breaks the pattern — most useful tool when scanning a patient with >50 moles.

— Record anatomic location, dimensions (long × short axis), color, configuration, and any change from prior photograph.

— Use total-body photography baseline images side-by-side with current exam for change detection.

Key distinction: A solar lentigo is a flat, uniformly tan, sharply demarcated macule on sun-damaged skin with a fingerprint-like dermoscopic pattern — it is not dysplastic and does not require biopsy. Confusing solar lentigines with dysplastic nevi leads to unnecessary procedures and is a common board distractor.

Full skin examination technique:

Clinical features of a dysplastic nevus:

Dermoscopy (10×–20× polarized magnification):

Ugly duckling and "little red riding hood" signs:

Documentation pearls:

Diagnostic Workup — Initial Evaluation and Indications for Biopsy

— Laboratory studies (CBC, LDH, LFTs) and imaging (CT, PET) are reserved for biopsy-proven melanoma with staging indications, not for surveillance of atypical nevi.

— Biopsy any lesion that is:

— Clinically suspicious for melanoma (ABCDE positive, ugly duckling, evolving).

— Symptomatic (persistent itch, bleeding, ulceration) without clear traumatic cause.

— Showing dermoscopic red-flag features.

— Documented change on serial photography.

— Monitor (photograph, recheck in 3 months) lesions that are mildly atypical clinically and stable.

— Reassure patients about lesions that are clinically and dermoscopically benign.

— Excisional biopsy with 1–3 mm margins down to subcutaneous fat is the gold standard — preserves architecture, depth (Breslow), and margins for pathology.

— Deep saucerization/scoop shave acceptable when full excisional biopsy is impractical (large lesion, cosmetically sensitive area) and the lesion is unlikely to be melanoma, but must capture full lesion depth.

— Avoid partial/incisional biopsies of pigmented lesions unless the lesion is too large for complete removal (e.g., facial lentigo maligna) — sampling error can miss invasive component.

— Punch biopsy is acceptable only for small lesions (<6 mm) where the entire lesion fits within the punch.

— Specify "rule out melanoma" and provide clinical context (size, location, change history).

— If atypia reported, request grading: mild, moderate, severe.

CCS pearl: When ordering a biopsy for a suspicious pigmented lesion in CCS, choose "excisional biopsy" with narrow margins; ordering "shave biopsy" of a lesion concerning for melanoma can be marked as a suboptimal step due to potential transection.

Initial workup is clinical and dermoscopic — there are no routine labs or imaging for dysplastic nevi.

Decision framework — biopsy vs. monitor:

Preferred biopsy technique:

Pathology request:

Diagnostic Workup — Pathology Interpretation and Genetic Testing

— Low-grade (mild–moderate) atypia: mild architectural disorder, small foci of cytologic atypia, retained maturation.

— High-grade (severe) atypia: marked architectural disorder, prominent cytologic atypia, may approach melanoma in situ; some pathologists use "severely atypical melanocytic proliferation."

— Mildly dysplastic nevus, margins clear: no re-excision; observe.

— Mildly dysplastic nevus, margins positive but no clinical residual pigment: observation acceptable; re-excision not required.

— Moderately dysplastic nevus, margins positive: observation generally acceptable per 2018 expert consensus, especially if no clinical residual lesion. Re-excise if clinical residual pigment.

— Severely dysplastic nevus, margins positive: re-excise with 2–5 mm margins to clear margins, given overlap with melanoma in situ.

— Severely dysplastic nevus, margins clear: observation; some experts re-excise to 2 mm.

— Comparative genomic hybridization (CGH), FISH for melanoma-associated chromosomal changes, or gene expression profiling (e.g., 23-gene signature) may help when histology is ambiguous (so-called "MELTUMP" or "SAMPUS" lesions).

— ≥3 melanomas in patient + first/second-degree relatives on same side of family.

— Melanoma + pancreatic cancer or astrocytoma in family (CDKN2A).

— Uveal melanoma, mesothelioma, renal cell carcinoma clustering (BAP1).

— Refer to genetic counseling before ordering CDKN2A/CDK4/BAP1 panels.

Board pearl: Routine sentinel lymph node biopsy is NOT indicated for severely dysplastic nevi or melanoma in situ — it's reserved for invasive melanoma with Breslow depth ≥0.8 mm or with high-risk features. Ordering SLNB for a dysplastic nevus is a wrong-answer choice.

Histopathologic grading of dysplasia (WHO 2018, simplified):

Margin management based on pathology:

Ancillary molecular studies (selected cases):

Germline genetic testing — indications:

Risk Stratification and Surveillance Cadence

— Counsel on self-skin exam monthly and sun protection.

— Routine clinician skin exams not universally recommended (USPSTF: insufficient evidence for screening in asymptomatic average-risk adults — "I" statement).

— Full skin exam every 6–12 months by primary care or dermatology.

— Baseline total-body photography if available.

— Patient self-exam monthly with partner assistance.

— Dermatology-led skin exam every 3–6 months, with dermoscopy and serial digital photography.

— Annual ophthalmologic exam for uveal melanoma in BAP1 carriers and CDKN2A families.

— Consider pancreatic surveillance (MRI/EUS) in CDKN2A families per NCCN.

— Stage 0–IIA: skin exam every 6–12 months × 5 years, then annually.

— Stage IIB–IV: every 3–6 months × 2 years, then every 3–12 months × 3 years, then annually.

— Broad-spectrum SPF ≥30 sunscreen, reapply q2h; UPF clothing; avoid peak UV 10 AM–4 PM; no tanning beds (Class I carcinogen).

— Self-skin exam technique with full-length and handheld mirrors; photograph suspicious lesions.

Step 3 management: For a 35-year-old with 50+ moles, 6 atypical nevi, and a sister with melanoma, the correct longitudinal plan is dermatology referral with baseline total-body photography and skin exams every 6 months — not prophylactic excision of all atypical nevi, which is invasive, scarring, and does not reduce melanoma mortality.

Risk-stratified surveillance is the core management decision in this topic.

Low risk (1–4 typical nevi, no atypia, no personal/family history of melanoma):

Moderate risk (multiple nevi, 1–4 clinically atypical nevi, single first-degree relative with melanoma):

High risk (≥5 atypical nevi, prior melanoma, FAMMM syndrome, CDKN2A carrier, organ transplant recipient):

Prior melanoma — surveillance schedule:

Patient education essentials (counsel at every visit):

Pharmacotherapy and Chemoprevention

— Broad-spectrum (UVA + UVB), SPF ≥30, water-resistant; apply 15 min before exposure, reapply every 2 hours and after swimming/sweating.

— RCT evidence (Australian Nambour trial): regular sunscreen use reduces invasive melanoma incidence by ~50% over 10 years.

— Mineral (zinc oxide, titanium dioxide) preferred in pregnancy and pediatric patients.

— 5-fluorouracil 5% cream and imiquimod 5% are used for actinic keratoses and superficial non-melanoma skin cancers — not for dysplastic nevi or melanoma.

— Topical retinoids: limited evidence for dysplastic nevus regression; not standard of care.

— ONTRAC trial: reduced new non-melanoma skin cancers by 23% in high-risk patients. No proven benefit for melanoma or dysplastic nevi, but often added in patients with multiple actinic keratoses and atypical nevi.

— Counsel: not niacin — does not cause flushing or affect lipids.

— Sun-protected patients can become deficient; check 25-OH vitamin D and supplement to maintain levels ≥20–30 ng/mL.

— Voriconazole long-term (associated with photo-induced SCC and melanoma) — discuss alternatives in transplant patients.

— Hydrochlorothiazide is associated with increased non-melanoma skin cancer; consider alternatives (e.g., chlorthalidone, ARB) in high-risk patients with multiple atypical nevi.

Board pearl: In a transplant recipient on azathioprine or voriconazole with multiple atypical nevi, the right answer often includes discussing medication change with the transplant team alongside intensified dermatologic surveillance — Step 3 rewards multidisciplinary, longitudinal thinking.

There is no FDA-approved pharmacotherapy specifically for dysplastic nevi. Management is surveillance, biopsy, and excision. However, several agents intersect with melanoma risk reduction and skin health.

Sunscreen as primary chemoprevention:

Topical agents:

Oral nicotinamide (vitamin B3) 500 mg BID:

Vitamin D:

Avoid:

Procedural Management — Excision Technique and Re-Excision Margins

— Informed consent: scar, infection, bleeding, recurrence, possibility of further excision if melanoma found.

— Local anesthesia: 1% lidocaine with epinephrine (avoid epi in digits/penis traditionally — though safety data now supports use; institutional preference).

— Elliptical excision with long axis parallel to skin tension lines, 3:1 length-to-width ratio, 1–3 mm clinical margins down to subcutaneous fat.

— Send specimen in formalin with orientation suture if margin status anatomically important.

— Acceptable for clearly benign-appearing nevi being removed for cosmesis or repeated irritation.

— Do not shave any lesion you would not be comfortable calling benign — transection of melanoma compromises depth assessment and staging.

— Mildly dysplastic, margin+ : no re-excision needed.

— Moderately dysplastic, margin+ without clinical residual: observe (2018 consensus).

— Severely dysplastic, margin+: re-excise 2–5 mm clear margins.

— Melanoma in situ: re-excise 5–10 mm margins (often 9 mm for lentigo maligna).

— Invasive melanoma:

— Breslow ≤1 mm → 1 cm margins.

— 1.01–2 mm → 1–2 cm.

— >2 mm → 2 cm.

— Petrolatum + non-stick dressing, daily cleansing; sutures out face 5–7 days, trunk 10–14 days, extremities 14 days.

— Scar maturation 6–12 months; silicone gel sheeting reduces hypertrophic scarring.

CCS pearl: After excising a lesion later read as invasive melanoma, the correct CCS next steps are wide local re-excision with appropriate margins, sentinel lymph node biopsy discussion for Breslow ≥0.8 mm, and referral to surgical/medical oncology — not "repeat skin exam in 1 year."

Office-based excisional biopsy (primary care or dermatology):

Shave/saucerization for low-suspicion atypical lesions:

Re-excision margins after pathology:

Cosmetically/functionally complex sites (face, ear, genitalia, acral): refer to Mohs surgeon or surgical dermatology for staged excision with margin control.

Wound care counseling:

Special Populations — Elderly and Organ Dysfunction

— New "mole" after age 50 is melanoma until proven otherwise — biopsy threshold is lower in older adults.

— Lentigo maligna (melanoma in situ on chronically sun-damaged skin) is the most common melanoma subtype on the head/neck of elderly patients; appears as slowly enlarging tan-brown macule with color variegation.

— Consider competing comorbidities and life expectancy when deciding on extensive re-excision; topical imiquimod or radiation are alternatives to wide excision for lentigo maligna in patients who are poor surgical candidates.

— Vision, manual dexterity, and cognition affect ability to perform self-skin exam — engage caregivers and increase clinician exam frequency.

— No direct effect on dysplastic nevus management.

— Lidocaine with epinephrine is safe; standard wound care unaffected.

— Avoid systemic NSAIDs for post-procedure pain in CKD stages 3–5; use acetaminophen ≤3 g/day.

— Reduce lidocaine maximum dose (hepatic metabolism); cap at 3 mg/kg without epi, 7 mg/kg with epi, and consider lower in cirrhosis.

— Coagulopathy (INR elevation, thrombocytopenia <50k) — correct or delay elective excisions; obtain hematology input.

— 65–100× increased risk of squamous cell carcinoma; melanoma risk 2–8×.

— Annual full-skin exam at minimum; every 3–6 months if prior skin cancer.

— Coordinate with transplant team to consider switching from calcineurin inhibitors to mTOR inhibitors (sirolimus, everolimus), which have lower skin cancer risk.

— Melanoma risk modestly increased; document baseline skin exam before initiation and annually.

Key distinction: A seborrheic keratosis on an elderly patient — waxy, "stuck-on," well-circumscribed, with horn pseudocysts — is benign and does not need biopsy. However, the sign of Leser-Trélat (sudden eruption of multiple seborrheic keratoses) raises concern for internal malignancy and warrants age-appropriate cancer screening review.

Elderly patients (>65 years):

Renal impairment / dialysis patients:

Hepatic impairment:

Solid organ transplant recipients:

Patients on biologics (anti-TNF, JAK inhibitors):

Special Populations — Pregnancy, Pediatrics, and Skin of Color

— Normal physiologic hyperpigmentation: linea nigra, melasma, darkening of existing nevi (especially on breasts/abdomen due to stretch).

— Any nevus with new asymmetry, border irregularity, or color change beyond uniform darkening warrants biopsy — pregnancy is not a contraindication.

— Local anesthesia with lidocaine ± epinephrine is safe (category B; preferred in 2nd–3rd trimester for elective procedures).

— Avoid: large-area imaging, systemic chemotherapy decisions deferred to maternal-fetal medicine + oncology; melanoma metastasis to placenta and fetus is rare but documented — examine placenta if maternal advanced melanoma.

— Congenital melanocytic nevi: small (<1.5 cm) — observe; large/giant (≥20 cm projected adult size) — refer to pediatric dermatology, monitor for melanoma (lifetime risk 2–5%) and neurocutaneous melanosis (MRI brain if multiple satellite nevi).

— Spitz nevi: pink-red dome-shaped papules in children; clinically and histologically can mimic melanoma — always biopsy atypical Spitz lesions and refer to dermatopathology.

— Childhood melanoma is rare but exists; ABCDE may not apply — pediatric criteria: Amorphous, Bleeding/bump, Color uniformity (often amelanotic), De novo development, any Diameter, Evolution.

— Melanoma incidence is lower but mortality is higher due to delayed diagnosis.

— Acral lentiginous melanoma is the most common subtype — examine palms, soles, subungual regions; Hutchinson sign (pigment extending onto proximal/lateral nail fold) is high-risk.

— Counsel that sunscreen and skin exams are still important; do not skip palms/soles/nails.

Step 3 management: A pregnant woman at 22 weeks with a changing 8 mm pigmented lesion on the back should undergo excisional biopsy under local anesthesia now, not deferred until postpartum — delay risks progression of an undiagnosed melanoma and is the wrong answer.

Pregnancy:

Pediatric considerations:

Skin of color (Fitzpatrick IV–VI):

Complications and Adverse Outcomes

— Progression to melanoma — though most dysplastic nevi do not become melanoma; instead they serve as markers of risk for melanoma developing elsewhere on the skin (often de novo on previously normal skin).

— Repeated trauma/irritation leading to bleeding or inflammation that mimics atypia clinically.

— Bleeding/hematoma: higher risk on scalp, back, anticoagulated patients. Hold elective procedures or use bridging strategy per ACC/CHEST guidance.

— Infection: 1–3% risk; higher on lower extremities, diabetics, immunosuppressed. Use sterile technique; routine prophylactic antibiotics not recommended.

— Scar formation: hypertrophic or keloid, especially on chest, shoulders, deltoids, ears; counsel before excision in these areas.

— Dehiscence: activity restriction post-excision (no heavy lifting × 2 weeks).

— Pigmentary alteration: post-inflammatory hyperpigmentation in darker skin types.

— Nerve injury: facial nerve branches, spinal accessory nerve in posterior triangle of neck — know anatomic danger zones.

— Recurrence (pseudomelanoma): re-pigmentation within the scar of a previously biopsied nevus; can histologically mimic melanoma — always communicate prior biopsy history to pathologist.

— Sampling error with partial biopsy — invasive component missed.

— Pathologist disagreement — atypical melanocytic lesions have notable interobserver variability; second opinion from dermatopathology is reasonable for moderate–severe atypia.

— Anchoring bias — assuming "patient already has dysplastic nevi, so this is another one" — leads to missed melanomas. Apply ugly duckling sign at every visit.

— Anxiety, "scanxiety" around skin exams; balance vigilance with reassurance.

Board pearl: A pigmented lesion that recurs within a previous biopsy scar with irregular features is the pseudomelanoma phenomenon; histology may show atypia but it is benign only if the pathologist knows about the prior biopsy — always provide clinical context on the requisition form.

Of the lesion itself:

Of the biopsy/excision procedure:

Diagnostic pitfalls:

Psychosocial:

When to Escalate Care — Referral and Specialty Triage

— Patient with ≥5 clinically atypical nevi or >50 total nevi.

— Family history of melanoma in ≥2 relatives.

— Personal history of melanoma at any stage.

— Any lesion where the primary clinician is not confident in the clinical assessment or biopsy technique.

— Anatomically complex sites (face, ears, genitalia, acral, subungual).

— Pediatric pigmented lesions with atypical features.

— Severe dysplasia or "atypical melanocytic proliferation, cannot exclude melanoma" diagnoses.

— Spitzoid lesions, deep penetrating nevi, blue nevus variants.

— Invasive melanoma requiring wide local excision with margins ≥1 cm.

— Lesions on functionally critical or cosmetically sensitive sites needing Mohs micrographic surgery or staged excision.

— Need for sentinel lymph node biopsy (Breslow ≥0.8 mm, or 0.8–1.0 mm with ulceration or high mitotic rate).

— Stage III (nodal) or IV (metastatic) melanoma — adjuvant immunotherapy (anti–PD-1 nivolumab/pembrolizumab) or targeted therapy (BRAF/MEK inhibitors for BRAF V600 mutated tumors).

— Familial atypical multiple mole melanoma syndrome (FAMMM).

— ≥3 melanomas in family, melanoma + pancreatic cancer, melanoma + astrocytoma, uveal melanoma + mesothelioma/RCC.

— BAP1 carriers, FAMMM with CDKN2A mutation — annual dilated eye exam for uveal melanoma surveillance.

Step 3 management: In a patient with 3 first-degree relatives with melanoma, one with pancreatic cancer, the longitudinal plan is dermatology surveillance every 3–6 months + genetic counseling for CDKN2A + ophthalmology annual exam + discussion of pancreatic surveillance with MRI/EUS in a high-risk pancreatic surveillance program — the multidisciplinary answer wins.

Refer to dermatology:

Refer to dermatopathology (second opinion):

Refer to surgical oncology / surgical dermatology:

Refer to medical oncology:

Refer to genetic counseling:

Refer to ophthalmology:

Key Differentials — Other Pigmented Lesions

— Uniform color, symmetric, sharp borders, stable over time. No biopsy unless changing.

— Flat, uniformly tan-brown, sun-exposed sites; sharp borders. Cosmetic concern only.

— Small (<5 mm), uniformly pigmented macules; can appear in childhood.

— Waxy, stuck-on, well-demarcated, often with horn cysts on dermoscopy; can be heavily pigmented and mimic melanoma — dermatoscopy is highly discriminative.

— Steely blue-black, deep dermal melanocytes, stable; biopsy if changing or atypical.

— Pink-red dome on child's face/extremity; can mimic melanoma histologically — biopsy for definitive diagnosis.

— Central nevus surrounded by depigmented halo from autoimmune-mediated melanocyte destruction; common in adolescents, benign. If halo around an atypical central lesion in an adult, biopsy.

— Flat, uniform light-brown patches; ≥6 of ≥5 mm (prepubertal) raises NF1 concern.

— Large unilateral pigmented patch with hypertrichosis on shoulder/back, often pubertal onset, benign.

— Superficial spreading (most common, trunk/extremities).

— Nodular (rapidly growing dome, often amelanotic, more aggressive — EFG: Elevated, Firm, Growing).

— Lentigo maligna (head/neck, elderly).

— Acral lentiginous (palms, soles, nails — most common in darker skin types).

Key distinction: Seborrheic keratosis has a "stuck-on" appearance and dermoscopic milia-like cysts and comedo-like openings; a dysplastic nevus is flatter, often with surrounding macular pigment ("fried egg"), and shows a reticular network on dermoscopy. Confusing the two leads to either unnecessary biopsy (SK) or missed melanoma (treating melanoma as SK).

Common acquired melanocytic nevus (junctional, compound, intradermal):

Solar lentigo ("liver spot"):

Lentigo simplex:

Seborrheic keratosis:

Blue nevus:

Spitz nevus:

Halo nevus:

Café-au-lait macules:

Becker melanosis / nevus:

Melanoma — the central differential to avoid missing:

Key Differentials — Non-Melanocytic Mimics

— Pearly, telangiectatic papule with focal pigment; dermoscopy: leaf-like areas, blue-gray ovoid nests, spoke-wheel structures. Biopsy if pearly translucent quality.

— Scaly erythematous plaque, may have pigmented variant; biopsy if persistent.

— Firm dermal papule, often on legs, "dimple sign" on lateral compression. Stable; not biopsied unless atypical.

— Friable bleeding red papule, often post-trauma or pregnancy; can be confused with amelanotic nodular melanoma — always send for histology after excision.

— Bright red to dark purple; dermoscopy shows lacunar pattern. Compressible (hemangioma) vs. firm with hyperkeratosis (angiokeratoma).

— Mimics subungual melanoma; history of trauma, grows out distally with nail growth over weeks. Persistent or non-migrating subungual pigment, especially with Hutchinson sign, requires nail matrix biopsy to exclude acral melanoma.

— Petechial pigment from athletic shear injury on heels; resolves with paring.

— Brown-black macule on palms/soles; KOH prep shows pigmented hyphae.

— Minocycline (blue-gray on shins, sclerae), amiodarone, hydroxychloroquine, chemotherapy (5-FU, bleomycin flagellate); pattern and drug history give diagnosis.

— Flat, uniform, often follows trauma or inflammation; history-dependent.

Board pearl: A persistent, dark, non-migrating longitudinal melanonychia stripe >3 mm wide, with variable color, on a single digit (especially thumb or great toe) in an adult, ± Hutchinson sign is subungual melanoma until proven otherwise — refer for nail matrix biopsy. "Reassure and observe" is a wrong answer.

Pigmented basal cell carcinoma:

Pigmented squamous cell carcinoma in situ (Bowen disease):

Dermatofibroma:

Pyogenic granuloma:

Hemangioma / angiokeratoma:

Subungual hematoma:

Talon noir / black heel:

Tinea nigra:

Drug-induced hyperpigmentation:

Café-au-lait / Becker / postinflammatory hyperpigmentation:

Secondary Prevention and Long-Term Plan

— Broad-spectrum SPF ≥30 sunscreen, ~1 oz per full-body application, reapply q2h and after swimming.

— UPF 50+ clothing, wide-brim hat, UV-blocking sunglasses.

— Seek shade 10 AM–4 PM; window film for cars (UVA penetrates glass).

— Absolute prohibition of tanning beds — Class I human carcinogen; document counseling.

— Monthly, head to toe, with full-length and handheld mirrors; engage partner for back, scalp, posterior thighs.

— Photograph suspicious lesions with smartphone next to a ruler for serial comparison.

— Use ABCDE and "ugly duckling" — teach by demonstration.

— Low risk: clinical judgment; high risk: every 3–6 months indefinitely.

— Wound care, suture removal timeline, signs of infection.

— When pathology results will be available (typically 5–10 days) and how they will be communicated — closed-loop communication is a patient-safety priority.

— If severe atypia or melanoma: scheduled in-person visit for results and counseling, not voicemail.

— Smoking cessation (impairs wound healing, increases SCC risk).

— Vitamin D supplementation if sun-restricted.

— Mental health support for cancer anxiety in FAMMM/high-risk patients.

— First-degree relatives of melanoma patients should undergo baseline skin exam and adopt sun-protection behaviors.

Step 3 management: After excising a severely dysplastic nevus with positive deep margins, the long-term plan is re-excision with 2–5 mm margins, dermatology surveillance every 6 months, total-body photography, sun protection counseling, and skin exam education for first-degree relatives — bundle these in one comprehensive answer.

Primary and secondary prevention overlap heavily in dysplastic nevus management:

Sun protection (lifelong, daily):

Self-skin examination:

Clinician surveillance schedule (see Chunk 6):

Discharge-equivalent counseling after biopsy of dysplastic nevus:

Lifestyle modifications:

Family education:

Follow-Up, Monitoring Parameters, and Counseling

— Suture removal: face 5–7 days, trunk/extremities 10–14 days.

— Pathology review visit: in-person or telehealth within 1–2 weeks; document discussion and plan.

— Wound check at 6 weeks if concern for scarring or infection.

— Number of nevi at baseline and over time.

— Number of atypical nevi.

— New lesions since last visit (date-stamped photographs).

— Change in existing lesions (size, color, symptoms).

— Cumulative biopsies and histologic results.

— Full-body skin exam performed (yes/no, areas examined).

— Body map or photo log updated.

— Patient education provided on sun protection and self-exam.

— Date of next planned exam.

— Reinforce sunscreen technique and reapplication.

— Confirm absence of tanning bed use.

— Address barriers to surveillance: cost, access, transportation, insurance.

— Discuss family screening if not already done.

— Adherence to recommended skin exam intervals.

— Time from biopsy to result communication (target ≤14 days).

— Re-excision performed within 4–6 weeks for severely dysplastic or melanoma diagnoses.

— Store-and-forward teledermatology is reasonable for triage of new lesions but not definitive for high-risk patients — in-person exam with dermoscopy remains gold standard for surveillance.

CCS pearl: When managing a patient after dysplastic nevus excision, advance the simulated clock to 6 months and re-order a full skin exam with dermoscopy; failing to bring the patient back is a common CCS error that lowers your score on longitudinal management.

Post-biopsy follow-up:

Surveillance metrics to track longitudinally:

Documentation standard at each visit:

Counseling content (every visit, dose-adjusted to risk):

Quality-of-care metrics (value-based context):

Telehealth role:

Ethical, Legal, and Patient Safety Considerations

— Discuss indications, alternatives (observation, photography), risks (scar, infection, bleeding, recurrence, possibility of re-excision if melanoma found), and the chance of needing further surgery.

— Use teach-back: have patient summarize what they understood.

— Document discussion in the chart, including specific risks named and alternatives offered.

— Establish a tracking system so no biopsy result is lost.

— Communicate all results to the patient — including benign findings — within 14 days.

— For malignant or severely atypical results, schedule in-person or video visit; do not leave melanoma diagnoses on voicemail.

— Failure to communicate a melanoma diagnosis is a leading source of dermatology malpractice claims.

— When transferring a patient between primary care and dermatology, send pathology reports, biopsy site photos, and surveillance schedule.

— On hospital discharge of a patient who had an incidental skin lesion noted, schedule outpatient dermatology follow-up explicitly — do not leave it to "patient will call."

— Avoid anchoring on prior benign biopsies; re-evaluate each lesion on its current merits.

— Use checklists (ABCDE, ugly duckling) to prevent omission.

— Acral and mucosal melanomas in patients with skin of color are often diagnosed late — examine palms, soles, nails, oral mucosa in all patients regardless of skin type.

— Discuss insurance coverage of dermatology referral, photography (often not covered), and genetic testing.

— Tanning beds are FDA Class II devices with mandatory black-box warnings; many states ban minors from use. Documenting counseling against use is good practice and protective.

Board pearl: A patient with a biopsy result of melanoma that was never communicated by the clinic and is found 18 months later with metastatic disease is a classic failure-of-communication malpractice scenario. Step 3 expects you to build a closed-loop result-tracking system as standard practice.

Informed consent for biopsy/excision:

Closed-loop pathology result communication (patient safety priority):

Transitions of care:

Cognitive bias mitigation:

Equity and access:

Mandatory reporting / public health: Not directly relevant to dysplastic nevi, but cancer registry reporting for confirmed melanoma is required in all US states.

Tanning bed counseling — legal context:

High-Yield Associations and Rapid-Fire Facts

Key distinction: A nevus that becomes darker uniformly in pregnancy is usually physiologic; a nevus that becomes asymmetric, irregularly bordered, or color-variegated in pregnancy is pathologic and warrants biopsy without delay.

FAMMM (familial atypical multiple mole melanoma) syndrome: ≥100 nevi, ≥1 atypical nevus ≥8 mm, family history of melanoma; CDKN2A germline mutation; also increased pancreatic cancer (lifetime risk up to 17%) and astrocytoma risk.

BAP1 tumor predisposition syndrome: uveal melanoma, cutaneous melanoma, mesothelioma, renal cell carcinoma, BAP1-inactivated melanocytic tumors (BIMTs — pink/red intradermal papules).

Xeroderma pigmentosum: autosomal recessive defect in nucleotide excision repair; melanoma + SCC + BCC at young ages; strict UV avoidance.

Albinism (OCA1/OCA2): absent or reduced melanin; high skin cancer risk; aggressive sun protection.

Tanning bed before age 35: 75% relative increase in melanoma risk.

Sentinel node biopsy threshold: Breslow ≥0.8 mm (or thinner with ulceration or high mitotic rate).

Most common melanoma subtype overall: superficial spreading (~70%).

Most common melanoma in darker skin: acral lentiginous.

Most aggressive melanoma: nodular (rapid vertical growth phase).

Lentigo maligna: in situ melanoma of chronically sun-damaged skin; head/neck of elderly; 5% lifetime progression to invasive lentigo maligna melanoma.

Breslow depth is the strongest prognostic factor for primary cutaneous melanoma — measured from granular layer to deepest invasion.

Ulceration upstages melanoma within each T category.

BRAF V600E mutations: ~50% of melanomas; targetable with dabrafenib/trametinib or encorafenib/binimetinib.

Adjuvant immunotherapy (nivolumab, pembrolizumab) is standard for stage III and resected stage IV melanoma.

USPSTF stance on routine skin cancer screening in asymptomatic average-risk adults: "I" — insufficient evidence (does not endorse or discourage).

Nicotinamide 500 mg BID reduces non-melanoma skin cancer; no proven melanoma benefit.

Board Question Stem Patterns

Step 3 management: When two answer choices are both "reasonable," pick the option that integrates longitudinal surveillance + patient education + multidisciplinary referral, not the single procedural choice.

Pattern 1 — Surveillance cadence: "A 32-year-old fair-skinned woman has 60+ nevi and 5 clinically atypical moles. Her sister was diagnosed with melanoma at age 28. Next best step?" → Refer to dermatology for baseline total-body photography and skin exams every 6 months. Wrong answers: prophylactic excision of all atypical nevi, annual whole-body CT, BRAF testing.

Pattern 2 — Biopsy technique: "A 5 mm pigmented lesion on the back is asymmetric with two colors and changed over 6 months. What is the best biopsy?" → Excisional biopsy with 1–3 mm margins to subcutaneous fat. Wrong answers: superficial shave, 4 mm punch from center, observe in 6 months.

Pattern 3 — Re-excision margins: "Pathology shows a severely dysplastic nevus with positive deep margin." → Re-excise with 2–5 mm clear margins. For melanoma in situ: 5–10 mm (often staged on face).

Pattern 4 — Pregnancy: "Pregnant 24 weeks, changing 7 mm lesion." → Excisional biopsy now under local anesthesia. Not "wait until postpartum."

Pattern 5 — Transplant patient with atypical nevi: → Skin exam every 3–6 months, discuss switching from calcineurin inhibitor to mTOR inhibitor with transplant team, intensive sun protection.

Pattern 6 — Subungual pigment: "Persistent 4 mm wide brown longitudinal nail band with extension onto cuticle (Hutchinson sign)." → Nail matrix biopsy to rule out acral melanoma.

Pattern 7 — Family history red flag: "Three relatives with melanoma, one with pancreatic cancer." → Genetic counseling for CDKN2A, dermatology surveillance, ophthalmology exam, pancreatic surveillance consideration.

Pattern 8 — Result communication failure: Patient never told about melanoma biopsy result. → Build closed-loop pathology tracking; communicate all results within 14 days.

Pattern 9 — USPSTF screening: → Insufficient evidence (I) for asymptomatic average-risk adults; high-risk patients still benefit from targeted surveillance.

One-Line Recap

Rapid recap bullets:

Board pearl: When in doubt on Step 3, the right answer pairs a definitive diagnostic action (excisional biopsy) with longitudinal multidisciplinary follow-up — never "reassure and return in a year" for a changing pigmented lesion.

The core teaching: Dysplastic nevi are markers of melanoma risk that require risk-stratified surveillance (every 6–12 months for moderate risk, every 3–6 months for high risk), excisional biopsy of any suspicious or changing lesion with 1–3 mm margins, and re-excision only for severely dysplastic lesions with positive margins or for invasive melanoma — not prophylactic removal of every atypical mole.

Biopsy: Excisional with 1–3 mm margins to subcutaneous fat is preferred. Shave acceptable only for clearly benign-appearing lesions; never use partial sampling on lesions concerning for melanoma. Send with clinical context to dermatopathology.

Re-excision margins: Mild dysplasia = no re-excision; moderate dysplasia with positive margin and no clinical residual = observe; severe dysplasia with positive margin = 2–5 mm re-excision; melanoma in situ = 5–10 mm; invasive melanoma = 1–2 cm based on Breslow depth; SLNB if Breslow ≥0.8 mm.

Surveillance hierarchy: USPSTF gives an "I" statement for routine population screening, but high-risk patients (FAMMM, ≥5 atypical nevi, prior melanoma, CDKN2A/BAP1 carriers, transplant recipients) need dermatology-led exams every 3–6 months, total-body photography, dermoscopy, and ophthalmology + genetic counseling when indicated.

Prevention and safety: Daily broad-spectrum SPF ≥30, UPF clothing, absolute avoidance of tanning beds, monthly self-skin exams with the "ugly duckling" rule, and closed-loop pathology result communication within 14 days are the patient-safety and longitudinal-care anchors that Step 3 tests repeatedly.