Case 43 Male, 82 years. Irregular variably pigmented lesion of 2,5 cm, lower backShow diagnosis & comments
Superficial spreading melanoma with partial regression
(PARTIAL) REGRESSION IN MELANOMAS:
Inflammatory infiltrates are common in melanomas, and should not be designated regression. Regression means elimination of melanoma, or parts of melanoma, by the inflammatory response, so that an area of superficial dermal scarring remains, often associated with focal inflammatory infiltrates, and, not uncommonly, presence of small nests of residual melanoma within the fibrotic deral tissue, or intradepidermal melanoma in the overlying epidermis.
Partial regression of melanoma manifests macroscopically as an area of flattening (in a raised lesion) with loss of pigmentation, or a bluish hue resulting from deep melanophages or residual pigmented melanoma cells. Eventually, the area of regression may come to closely resemble normal skin.
If all dermal and epidermal melanoma is eliminated by the inflammatory process, only scar tissue and often scattered or grouped melanphages remains. Such complete regression of a primary melanoma is probably one of the scenarios that result in metastatic melanoma with unknown primary tumour. In some instances, large masses of melanophages have been produced; such so-called 'tumoral melanosis' is insufficient for a formal diagnosis of (previous) melanoma, but is is very likley that most if not all such lesions result from previous melanoma with abundant melanin production, whjich has completely regressed.