Melanoma
A malignant proliferation of melanocytes that, unlike a benign naevus, grows asymmetrically and eventually invades vertically into the dermis, and it is the depth of that invasion at diagnosis, the Breslow thickness, that is the single strongest predictor of survival.
In a nutshell
A melanocyte clone escapes normal growth control, first spreading radially (giving the ABCDE features) then invading vertically into the dermis. Breslow thickness, how deep it has gone, is the dominant driver of prognosis, excision margin and further staging.
Classic presentation
A changing or new asymmetrical, irregularly-bordered, variably-coloured pigmented lesion, sometimes itching or bleeding.
Key points
- ABCDE and the weighted 7-point checklist both capture the same underlying feature: uncoordinated, ongoing clonal growth versus a stable benign naevus.
- Breslow thickness, not subtype, is the key prognostic factor and determines excision margin and need for sentinel node biopsy.
- Diagnosis requires full excision biopsy, not a shave or punch biopsy, so the deepest point of invasion is not missed.
- Suspicious lesions go via the 2-week-wait pathway: early excision while thin is curative.
- Metastatic melanoma is treated with immunotherapy or targeted BRAF/MEK inhibitors rather than surgery alone.
First-line investigation
Dermoscopy followed by full excision biopsy of the suspicious lesion to measure Breslow thickness histologically.
First-line management
Urgent 2-week-wait excision biopsy, followed by wide local excision with a margin scaled to the measured Breslow thickness.
Exam traps
- A shave or punch biopsy of a suspected melanoma is the wrong answer: excision biopsy is required to measure Breslow thickness accurately.
- Amelanotic melanoma can lack obvious pigment, so a pink, changing, bleeding nodule should not be dismissed just because it isn't dark.
- Prognosis correlates with Breslow thickness, not lesion diameter or subtype alone.
Educational content pending clinical review. Not medical advice.