Giant congenital melanocytic nevus associated with lipoma in an Indian man.

Congenital melanocytic nevus is a inborn melanocytic proliferation either present since birth or soon afterward and shows characteristic histopathological features comprising proliferation of benign melanocytes and extension of nevus cells into the deep reticular dermis and subcutis. We report the case of a 35-year-old male patient who presented with a progressively enlarging soft tissue mass in bilateral flank region. High-resolution ultrasound imaging showed multiple lipomatous masses within the soft tissues on the either flank region. Subsequent excision of the soft tissue mass showed a well-circumscribed lipomatous lesion with diffuse infiltration by benign appearing melanocytes within the fat lobules established by immunohistochemistry, which was positive for HMB45 and S100. This case serves to illustrate the initial diagnostic challenge in a male patient as well as the plasticity of the neural crest cells.