A 65-year-old man presents with a slowly enlarging, dark-brown to black, asymmetric macule on the left cheek with irregular borders and variegated pigmentation. Dermoscopy shows regression structures, atypical pigment network, and grey pepper-like dots. An excision biopsy is performed. Which histopathological finding would indicate the WORST prognosis according to the current AJCC staging system?

• A Clark level III invasion (into papillary dermis)
• B Breslow thickness less than 1 mm without ulceration and mitotic rate <1/mm²
• C Breslow thickness greater than 4 mm with ulceration (T4b) ✓
• D Presence of tumour-infiltrating lymphocytes (brisk pattern)

Explanation

In the current AJCC 8th edition staging for melanoma, Breslow thickness (vertical tumour depth in mm) is the primary prognostic determinant for the T category, with ulceration as a major upstaging modifier. T4b (thickness >4 mm with ulceration) carries the worst prognosis among primary tumour characteristics, conferring approximately 50% 5-year survival even without nodal involvement. Clark level is now used only for T1 staging (thin melanomas <1 mm) and only when mitotic rate is unavailable. Brisk tumour-infiltrating lymphocytes are a favourable prognostic indicator, not unfavourable.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.