Double cancer of plantar malignant melanoma and vulvar extramammary Paget’s disease

A 75‐year‐old woman presented with a 2‐year history of a pigmented nodular lesion on her left sole and a 9‐year history of a red infiltrative plaque on the vulva. The plantar lesion was a 15‐mm ulcerated nodule located at the center of a 25‐mm atypical pigmentation region; the nodule was clinically suspected to be a malignant melanoma. Histopathological analysis of the vulvar lesion biopsy sample indicated extramammary Paget’s disease (EMPD). There was no evidence of metastasis in the computed tomography (CT) and ¹⁸F‐fluorodeoxyglucose positron emission tomography scans. We simultaneously performed a wide excision of both lesions and a left inguinal sentinel lymph node biopsy. Melanoma cells were identified in the sentinel lymph nodes, and left radical lymph node dissection was performed after a course of neoadjuvant chemotherapy. All the lymph nodes that were resected during the second operation tested negative for melanomas, and the plantar lesion was diagnosed as a stage IIIB malignant melanoma (pT4b, Na2, M0). Thereafter, we administrated four courses of chemotherapy, and 8 months after the operation, there was no evidence of recurrence or metastatic lesions. We present a case report of double cancer: a plantar malignant melanoma and vulvar EMPD, and also discuss the possible genetic mutations responsible for these two tumors.