2019 Volume 33 Issue 3 Pages 173-178
A 65-year-old man presented with a red-brown nodule and a brown-black macule at the periphery of a brown plaque measuring 14×3cm on the right side of his back. Although the brown plaque was a congenital lesion, the nodule was recently detected by his primary care physician. Histopathological examination of the lesion revealed a compound nevus and concomitant malignant melanoma showing solitary proliferation and nests of atypical melanocytes in the epidermis and superficial dermis. The tumor thickness was 2.7 mm. Positron emission tomography-computed tomography showed no metastasis. We excised the lesion with a 2-cm margin from the scar at the biopsy site and a 5-mm margin from the nevus. After excision, right axillary and inguinal sentinel lymph node biopsies, followed by right axillary lymphadenectomy, were performed. Based on these results, we diagnosed him with malignant melanoma (pT3aN1aM0, stage IIIA). We administered 3 courses of postoperative interferon beta therapy, and no recurrence or metastasis has occurred during 1-year follow-up. Although malignant melanoma rarely originates in a medium-sized congenital melanocytic nevus, it is important to educate patients regarding the need for prompt dermatological consultation if a lesion changes in color and/or form.[Skin Cancer (Japan) 2018 ; 33 : 173-178]
