部分的に自然消退傾向を示した背部表在性拡大型黒色腫の1例

抄録

We report a case of superficial spreading melanoma with partial spontaneous regression.
A 30-year-old man presented with a eight year-history of gradually enlarging brownish macule on his back. Five years ago, a part of the macule began to elevate and formed a papule. Simultaneously, the center of the macule began to regress. Histopathological observation of the papule showed that many nests of melanoma cells were found in the epidermis and the upper dermis. Intence infiltrations of inflammatory cells were found periphery to the tumor. The observations of the pigmented macule showed that atypical melanocytes were scattered in the basal cell layer and many lymphocytes were found in the upper dermis. The observation of the regressed lesion revealed dense inflammatory infiltrates composed mainly of lymphocytes and melanophages, and dermal fibrosis. Tumor thickness was 0.85mm. Accordingly, we diagnosed this case as a stage I melanoma. Immunohistological analysis of the macule showed that tumor cells were positive for both S-100 protein and HMB-45. Infiltrations of CD4⁺ and CD8⁺ cells were mainly detected around the foci of tumor cells, and more CD4⁺ cells than CD8⁺ cells were seen. It seems likely that T-cell immunity may have been involved in regression of the tumor.