# Tumoral Melanosis: A Benign Mimicker of Malignant Disease

## TL;DR

A patient undergoing melanoma treatment developed benign pigmented lesions mistaken for cancer, highlighting the need for biopsies to avoid misdiagnosis.

## Contribution

This case highlights tumoral melanosis as a benign condition that can mimic melanoma progression during immunotherapy.

## Key findings

- Biopsies revealed melanin-laden macrophages without melanocytes, consistent with tumoral melanosis.
- The lesions were surrounded by vitiligo-like halos and occurred during treatment with nivolumab and ipilimumab.
- The case emphasizes the importance of histopathological evaluation to prevent misdiagnosis of metastatic disease.

## Abstract

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.