Tumoral melanosis after immunotherapy with pembrolizumab - a response sign mimicking melanoma

Tumoral melanosis associated with nivolumab therapy for metastatic melanoma

“…Most cases described in this report showed a favorable clinical response, with nine out of ten patients being alive after the follow-up period [12]. These data are consistent with those described in other single case reports [9][10][11]. In contrast, diffuse melanosis (DM) is associated with poor prognosis.…”

“…Exceptionally, it has also been reported in regressed pigmented epithelial lesions [8]. As in our case, its metastatic appearance makes a skin biopsy necessary, with immunohistochemistry demonstrating positivity for CD68 and absence of neoplastic cells with SOX-10, HMB-45 and Melan-A [5][6][7][8][9][10][11][12]. The prognosis is still unclear due to the limited number of reported cases with long-term follow-up so far [5][6][7][8][9][10][11][12].…”

“…The underlying mechanism of TM is not yet fully understood. It may be related to an increase in T-cell mediated apoptosis, which could suggest a therapeutic response [5][6][7][8][9][10][11][12]. Accordingly, the lesions observed in our patient could correspond to in-transit tumor cells previously undetected in the extension study, and which would have been destroyed by the nivolumab-driven immune response.…”

“…Firstly, as a completely regressed melanoma, usually associated with an aggressive clinical course and metastatic disease. Secondly, in advanced melanoma treated with immunotherapy (mainly pembrolizumab and less frequently nivolumab, ipilimumab) or BRAF inhibitors [3][4][5][6][7][8][9][10][11]. Exceptionally, it has also been reported in regressed pigmented epithelial lesions [8].…”

Gray-black macules in a patient with melanoma

“…Tumoral melanosis is a rare cutaneous response associated with partial or complete regression of melanoma. 1 , 2 Tumoral melanosis presents as darkly pigmented macules, papules, or nodules and often mimics the appearance of melanoma warranting biopsy. 1 Histologically, densely grouped melanophages, but not melanocytes, are present in the dermis and correlate with the pigmented lesions observed clinically.…”