Lentigo Maligna Melanoma (LMM) is a melanocytic neoplasm arising from 5% of Lentigo Maligna (LM) subtype. Both LM and LMM are considered rare in brown skin.
A 58-year-old man with Fitzpatrick Skin type IV-V, a farmer with a history of intermittent sun exposure during his childhood, sought consult for a pigmented patch on the right forearm. Forty years prior to consult, patient noted the appearance of solitary, dark brownish, and gradually increasing macule on the right forearm which became brownish-black in color over the years. Depigmented areas on the plaque and a mass the size of a golf ball on the right axilla were noted 3 months prior to consult. Dermatological examination revealed a 1x2cm solitary, ill-defined, irregularly shaped brownish black patch on the dorsal surface of the right forearm with areas of depigmentation. Dermoscopy revealed asymmetric black nests and clods, blue white veil, white areas, rhomboidal structures with asymmetric follicular openings, and multiple black dots. Clinical diagnosis was LMM and was validated by histopathological examination. Atypical melanocytes were highlighted by Melan-A stain. Excision of the right axillary mass showed melanoma of the lymph node. Referral to an Oncologist who recommended radiotherapy was done. No recurrence on the forearm lesion or lymphadenopathy were observed after 1 year of follow-up.
In a country where melanoma is rarely observed, dermoscopy plays an important tool in the immediate diagnosis of malignant pigmented lesions.Histopathology remains to be the gold standard but the practice of dermoscopy is expected to fast track melanoma diagnosis and proper management.