PDM is considered a rare

PDM is considered a rare subtype of solitary melanoma confined to the purchase CB-5083 and/or subcutaneous tissue with no known separate primary melanoma and negative metastatic findings on work-up. PDM shows a much better prognosis compared with similarly staged cutaneous melanoma, and 5-year survival rate is as high as 80–100%. An associated benign intradermal nevus is histopathologically detected in 29% (14/49) of PDM cases, which was not found in our case. Our case is probably the first amelanotic type of PDM reported in English literature. No melanization was found with negative immunohistochemical results for Melan-A, HMB-45, and MITF; however, additional staining for tyrosinase eventually led to the diagnosis of melanoma. While tyrosinase antibody is rarely used in Japan, it is used in the form of a pan-melanoma antibody cocktail including Melan-A and HMB-45. In our case, the tumor was not likely to be a recurrence of malignant melanoma, because the laser ablation was done 16 years ago. The possibility of melanoma development subsequent to laser treatment of histologically diagnosed benign lesions was reported. It was also reported that sublethal laser damage could increase p16 expression, and mutation is detected in most benign melanocytic nevi as well, not just in melanoma. The association of the incidence of V600E mutation and clinical subtypes was not statistically significant, which showed that mutation was detected in 37.7% of superficial spreading melanoma, 30.2% of nodular melanoma, 17.0% of lentigo maligna, and 15.1% of acral or mucosal melanomas. Although histological examination was not done before the laser treatment and we could not find dermal component of benign nevus in the resected tumor, laser treatment in our case might still possibly induce malignant transformation of dermal nevus cells harboring BRAF mutation. Acknowledgments
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