Amelanotic melanoma presented as multiple flesh-coloured islands

A 97-year-old man visited the dermatology department of Taipei Veterans General Hospital in February, 2023, with a 3-month history of painful skin lesions on his right sole. The lesion began with painful papules and progressed to multiple plaques with ulceration and bleeding. The patient denied recent episodes of fever, chills, or involuntary weight loss. On physical examination, multiple islands of flesh-coloured, indurated plaques with ulcerated borders and crust formation were noted (figure, A). No laboratory abnormalities were found. An incisional biopsy of the lesion revealed nests of melanocytes with pleomorphism and marked atypia in the epidermis and the reticular dermis (figure, B). There was also Pagetoid spreading of melanocytes and ulceration in the epidermis. An invasive amelanotic melanoma with a Breslow thickness of 1·2 mm was confirmed, identified through positive MART-1, SOX-10, and PRAME immunohistochemical stains and a negative p63 stain. Genetic testing for BRAF mutation was negative. 1 week after diagnosis, the patient developed dyspnoea, and chest CT found multiple lung nodules. Owing to his age and the concern of advanced melanoma, the patient was referred to the oncology department for discussion of palliative therapeutic options. Intravenous pembrolizumab 2 mg/kg every 3 weeks was initiated. The lesions on the right sole gradually improved, and the patient's condition remained stable at the most recent follow-up in July, 2023.