Tumoral melanosis, also known as nodular melanosis or melanophagocytosis, refers to the histopathologic presence of pigment-laden macrophages that has developed at the site of a regressed pigmented lesion. It is a very rare phenomenon, presenting clinically as one or more gray, gray-blue, blackish, or violaceous macules, papules, nodules, or plaques.

Tumoral melanosis is usually observed from completely regressed melanocytic proliferations, including a primary malignant melanoma. In these cases, it may appear at the site of the primary tumor or at sites of cutaneous metastases, and the phenomenon is often associated with the presence of metastatic melanoma. Most recently, melanoma-associated tumoral melanosis has been described in patients with metastatic melanoma undergoing immunotherapy, such as with talimogene laherparepvec, ipilimumab, nivolumab, and pembrolizumab, as well as dabrafenib and trametinib. In these patients, tumoral melanosis usually occurs nearby the primary melanoma excision site or at the site of prior in-transit metastases.

Tumoral melanosis has also rarely been observed after regression of pigmented epithelial lesions, such as pigmented basal cell carcinoma, pigmented Bowen disease, seborrheic keratosis, solar lentigines, pigmented epithelial lined cysts, and benign nevi. Other pathologies described in the literature associated with this finding include mycosis fungoides and blastic plasmacytoid dendritic cell neoplasm (BPDCN).
Even more rarely, tumoral melanosis has been reported in the lymph nodes, known as nodal melanosis. Anecdotally, it has also been found in the visceral organs of 2 patients.