Tumoral Melanosis

An 84-year-old man with a history of melanoma on the right forehead, complicated by in-transit metastases to the scalp, developed blue-gray macules after receiving immunotherapy.

Seven months after starting treatment, his scalp nodules shrank, leaving behind gray spots. A dermoscopy-guided biopsy of four lesions showed melanin-laden macrophages in the superficial and middle dermis, without residual melanoma. Immunohistochemical staining for melanoma markers was negative, confirming tumoral melanosis, a benign pigmented skin lesion that occurs after melanoma regression, sometimes as a response to immunotherapy.

Tumoral melanosis can mimic metastatic melanoma, but absence of nodules supports the diagnosis. Histologic assessment is crucial to differentiate between melanoma metastases and tumoral melanosis. The patient continues dermatologic surveillance, as new papules or nodules warrant biopsy for melanoma recurrence.

An 84-year-old man with a history of melanoma on the right forehead, complicated by in-transit metastases to the scalp, developed blue-gray macules after receiving immunotherapy.

Seven months after starting treatment, his scalp nodules shrank, leaving behind gray spots. A dermoscopy-guided biopsy of four lesions showed melanin-laden macrophages in the superficial and middle dermis, without residual melanoma. Immunohistochemical staining for melanoma markers was negative, confirming tumoral melanosis, a benign pigmented skin lesion that occurs after melanoma regression, sometimes as a response to immunotherapy.

Tumoral melanosis can mimic metastatic melanoma, but absence of nodules supports the diagnosis. Histologic assessment is crucial to differentiate between melanoma metastases and tumoral melanosis. The patient continues dermatologic surveillance, as new papules or nodules warrant biopsy for melanoma recurrence.