Diffuse cutaneous melanosis: rare complication of metastatic melanoma

Abstract

Diffuse cutaneous melanosis is a rare complication of metastatic melanoma related to a worse prognosis. There are few cases reported in the literature. Its pathogenesis has not been completely elucidated, although studies have suggested certain mechanisms for its occurrence. It is clinically manifested as a blue-gray discoloration of the skin and mucous membranes in a cephalo caudal progression and usually associated with melanuria. Skin and mucosa histopathology reveals only the presence of melanophages in the dermis, mainly perivascular, and free interstitial melanin. We report the case of a 68-year-old male with metastatic melanoma, diffuse hyperpigmentation of the skin and melanuria.

Diffuse melanosis secondary to metastatic melanoma in a Nelore bull

“…In cases of diffuse cutaneous melanosis, metastases of malignant melanoma occur in the liver, lungs, lymph nodes, spleen, intestines, and heart (6). In such instances, melanuria occurs (1,11), confirmed by the melanophages and melanin in the urine (6). The histologic and immunohistochemical findings in the current case, along with diffuse black discoloration and organomegaly in several tissues, support the diagnosis of generalized (or multicentric) melanosis secondary to metastatic melanoma in the current case.…”

“…Those include the conversion of melanin precursors in the circulation or the dermal melanophages before complete oxidation into melanin; the deposition, in the skin, of pigment granules arising from the neoplasm or the sites of metastases; or even due to an unlimited propagation of melanoma cells that are capable of producing melanized melanosomes (5,15,16). In such cases, emaciation, black discoloration of the skin and urine, hepatomegaly, and metastases mainly in the lung and liver are described (1). In cases of diffuse cutaneous melanosis, metastases of malignant melanoma occur in the liver, lungs, lymph nodes, spleen, intestines, and heart (6).…”

“…Melanosis is hyperpigmentation of various tissues and organs not usually pigmented, resulting from overproduction and accumulation of melanin due to abnormal migration of melanocytes during embryogenesis, in this case without much clinical significance, or even, although rare, due to an association with malignant melanomas (1,4,8,10,11). Malignant melanomas are common in dogs, may constitute 10-15% of the melanocytic tumors in miniature Sinclair pigs, and are uncommon in cats.…”

Duodenal Pseudomelanosis: A Literature Review

“…The term "pseudomelanosis" should therefore be applied to pigmentations that may resemble melanin deposition but with the demonstration of a different type of underlying pigment [9,29]. The two terms are not synonyms, as true melanosis in different organ sites refers to different clinical settings and has different implications [30,31]; however, they are widely used as synonyms in cases of diffuse pigmentation of the colon associated with excessive laxative use, with deposition of lipofuscin (melanosis coli) [32]. In practical terms, DP refers to a distinct endoscopic presentation, with pigmentation limited at the apex of the villi.…”