腫瘍性黒色腫：悪性疾患を模倣する良性疾患

We report the case of a 60-year-old male with metastatic melanoma originating from a hyperpigmented lesion on the hard palate. During treatment with nivolumab, ipilimumab, cisplatin, and temozolomide, he developed multiple bluish macule-like lesions on the retroauricular region, neck, and anterior chest, surrounded by vitiligo-like halos. Given the clinical suspicion of in-transit metastases, biopsies were performed. Histopathological evaluation revealed dermal aggregates of melanin-laden macrophages, positive for CD68, in the absence of melanocytes, findings characteristic of tumoral melanosis. This case underscores the importance of biopsy for new pigmented lesions arising during melanoma immunotherapy. Recognizing tumoral melanosis is essential to avoid misinterpretation as disease progression and to guide appropriate clinical management.