About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- Any new or changing pigmented lesion is melanoma until assessed: use ABCDE plus the ugly-duckling sign and patient-reported evolution
- Do not reassure a lesion simply because it is small; evolution, asymmetry, irregular border, colour variation, symptoms, and patient concern matter
- Suspicious melanoma should usually be removed by narrow excisional biopsy where feasible; avoid superficial shave of a lesion suspicious for invasive melanoma
- Non-melanoma skin cancers may be pearly, ulcerated, crusted, non-healing, tender, hyperkeratotic, or bleeding rather than deeply pigmented
- Counsel on sun protection, tanning-bed avoidance, self-skin examination for high-risk patients, and timely follow-up of biopsy results
Approach to the Presentation
The clinical task in a pigmented or otherwise suspicious skin lesion is not to name every benign lesion, but to decide whether malignancy needs biopsy or urgent referral. Ask about onset, growth, evolution, bleeding, ulceration, pain, itch, trauma, prior skin cancer, immunosuppression, organ transplant, tanning-bed use, severe sunburns, family history of melanoma, and number of atypical naevi. Examine the lesion and the surrounding skin in good light, compare it with the patient's other moles, and inspect regional lymph nodes if melanoma is suspected. Document size, colour, border, surface, ulceration, and location. The exam commonly tests ABCDE, ugly-duckling recognition, and the correct next best step: biopsy or urgent referral rather than watchful waiting when melanoma is plausible.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Melanoma | must-not-miss | Asymmetry, irregular border, colour variation, diameter often >6 mm, evolution, bleeding, itch, ulceration, ugly-duckling lesion; may be amelanotic | Narrow excisional biopsy with histopathology; urgent dermatology/plastic surgery if site or size makes biopsy difficult |
| Squamous Cell Carcinoma | must-not-miss | Scaly, hyperkeratotic, tender, crusted or ulcerated papule/plaque on sun-exposed skin; higher risk in immunosuppression, scars, chronic ulcers | Skin biopsy; assess high-risk features and regional nodes |
| Basal Cell Carcinoma | must-not-miss | Pearly papule with telangiectasia, rolled border, central ulceration, non-healing sore; superficial BCC may be erythematous scaly patch | Skin biopsy; dermoscopy may show arborizing vessels |
| Merkel Cell Carcinoma | must-not-miss | Rapidly growing painless firm red-blue or violaceous nodule in older or immunosuppressed patient; often sun-exposed | Urgent biopsy and oncology/dermatology referral |
| Seborrhoeic Keratosis | common | Waxy stuck-on verrucous plaque, variable pigmentation, multiple lesions in older adults; can become irritated | Clinical/dermoscopic diagnosis; biopsy if atypical or changing because melanoma can mimic it |
| Benign Melanocytic Naevus / Dysplastic Naevus | common | Stable symmetric pigmented macule or papule; dysplastic lesions may be larger with irregular colour but stable over time | Serial photography/dermoscopy for selected low-risk lesions; biopsy if changing or suspicious |
| Actinic Keratosis | common | Rough gritty erythematous or hyperkeratotic macule/papule on sun-exposed skin; premalignant SCC precursor | Clinical diagnosis; biopsy if thick, tender, ulcerated, rapidly growing, or treatment-resistant |
| Dermatofibroma | common | Firm hyperpigmented papule/nodule, often on legs, dimples inward with lateral compression | Clinical diagnosis; biopsy if atypical, growing, symptomatic, or uncertain |
| Pyogenic Granuloma | common | Friable rapidly growing red papule/nodule that bleeds easily; pregnancy, trauma, or medication associations | Excision/curettage with histology to exclude amelanotic melanoma or SCC |
| Lentigo / Solar Lentigo | common | Flat tan-brown macule on sun-exposed skin, stable, uniform pigmentation; lentigo maligna is the malignant mimic | Dermoscopy/biopsy if irregular, enlarging, variegated, or on chronically sun-damaged face |
| Kaposi Sarcoma / Vascular Lesion | rare | Violaceous macules, plaques, or nodules; immunosuppression or HIV risk; may involve mucosa | Biopsy; HIV testing when clinically appropriate |
Red Flags & Key History
Symptoms
Evolution: new, enlarging, changing shape/colour, bleeding, crusting, ulcerating, itching, or painful lesion
Personal history of melanoma or non-melanoma skin cancer
Family history of melanoma, multiple atypical naevi, blistering sunburns, tanning-bed exposure
Immunosuppression, organ transplant, HIV, chronic lymphocytic leukaemia, or biologic therapy
Non-healing sore despite appropriate wound care
Stable waxy stuck-on lesion for years — favours seborrhoeic keratosis
Firm papule that dimples with compression — favours dermatofibroma
Signs
ABCDE: asymmetry, border irregularity, colour variation, diameter, evolution
Ugly-duckling lesion that looks different from the patient's other naevi
Ulceration, spontaneous bleeding, induration, tenderness, rapid growth
Pearly rolled border with telangiectasia
Hyperkeratotic tender nodule or cutaneous horn on sun-exposed skin
Regional lymphadenopathy near suspicious melanoma or SCC
Approach to Investigation
First-line
Clinical skin examination with ABCDE and ugly-duckling assessmentCompare lesion with the patient's background mole pattern and document size, site, colour, border, surface, ulceration, and symptoms
Dermoscopy if trained/availableImproves recognition of melanoma and benign mimics but does not replace biopsy when suspicion is high
Regional lymph node examinationPalpate draining nodal basins if melanoma, SCC, Merkel cell carcinoma, or thick/ulcerated lesion is suspected
Photograph and measure only when appropriateUseful for clearly low-risk lesions being monitored; not appropriate for a lesion with strong melanoma features
Second-line
Excisional biopsyPreferred for suspicious melanoma where feasible: narrow margins and full-thickness specimen to allow Breslow depth measurement
Punch, incisional, or shave biopsyMay be appropriate for large lesions, cosmetically sensitive sites, or suspected non-melanoma cancers; avoid superficial shave if invasive melanoma is suspected
Histopathology with margin and depth reportingMelanoma management depends on Breslow thickness, ulceration, mitotic rate, margins, and staging features
Specialist
Urgent dermatology/plastic surgery referralFor lesions suspicious for melanoma when primary care biopsy is not feasible, or for high-risk non-melanoma skin cancer on face, ear, lip, genitalia, hands/feet, or immunosuppressed patients
Oncology/surgical oncology stagingFor confirmed melanoma, Merkel cell carcinoma, advanced SCC, nodal disease, or recurrent/aggressive tumours
Management Principles
Cancer Care Ontario skin cancer guidance + Canadian Dermatology Association skin cancer resources1
Decide: reassure, monitor, biopsy, or refer
- Reassure only when the lesion is confidently benign and stable
- Use short-interval review/photography only for low-risk uncertain lesions, not high-risk evolving lesions
- Biopsy or refer urgently when melanoma, SCC, BCC in high-risk site, Merkel cell carcinoma, or non-healing ulcer is possible
2
Biopsy principles
- For suspected melanoma, obtain a full-thickness excisional biopsy with narrow margins where feasible
- Do not destroy a suspicious pigmented lesion with cryotherapy, cautery, or laser before histology
- Ensure biopsy results are actively tracked and communicated to the patient
3
Prevention and counselling
- Advise sun protection: shade, protective clothing, broad-spectrum sunscreen, and avoidance of tanning beds
- Teach ABCDE and ugly-duckling self-awareness for high-risk patients
- Discuss risk factors and arrange periodic professional skin examination based on individual risk and local access pathways
4
Follow-up after diagnosis
- Melanoma: definitive excision margins and sentinel node/staging decisions depend on pathology
- BCC/SCC: treatment options include excision, Mohs surgery in selected high-risk sites, curettage/electrodesiccation, topical therapy for selected superficial disease, or radiotherapy in selected cases
- Immunosuppressed patients need lower threshold for referral and surveillance
Complications & Pitfalls
- Reassuring a changing lesion: Evolution is often the most important melanoma clue.
- Destroying without diagnosis: Never freeze, laser, or cauterize a suspicious pigmented lesion before histology.
- Superficial shave of suspected melanoma: This may prevent accurate Breslow depth measurement.
- Ignoring amelanotic melanoma: Melanoma can be pink, red, or non-pigmented and may mimic pyogenic granuloma or eczema.
- No biopsy tracking system: A missed malignant biopsy result is a patient-safety failure.
MCCQE1 Exam Tips
- 1The classic melanoma clue on exams is evolution: changing size, colour, shape, symptoms, or bleeding
- 2ABCDE is necessary but not sufficient; the ugly-duckling sign is highly useful in vignettes with multiple naevi
- 3Next best step for suspicious melanoma is excisional biopsy, not reassurance, antibiotics, cryotherapy, or long-term observation
- 4A pearly papule with rolled border and telangiectasia is BCC; a tender hyperkeratotic lesion is SCC until proven otherwise
- 5Amelanotic melanoma may look like a pink bleeding papule; pyogenic granuloma-like lesions still need histology
- 6Regional lymph nodes matter in suspected melanoma, SCC, and Merkel cell carcinoma
- 7Counselling is part of the MCC answer: sun protection, tanning-bed avoidance, and follow-up of results
practicetest your knowledge on skin lesion / pigmented lesionApply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — dermatologic and beyond.
open q-bank