Histologic examination showed a scantily pigmented dermal nodule, characterized by considerable nuclear polymorphism. The cells were arranged as sheets, with no maturation of cells with descent into the dermis. There was a narrow zone of normal collagen separating the tumor from overlying atrophic epidermis. Infiltration of tumor cells into vessels was observed. Tumor cells were positive for antibodies to HMB-45 and to S100 protein.
A primary lesion could not be found on skin examination, and the patient underwent a thorough examination of the superficial lymphatic system; an eye, ear, nose and throat examination; and a rectocolonoscopy. None of the tests revealed a primary lesion.
Multiple Papulonodular Lesions on the Arm. Arch Dermatol. 2001;137(7):957-962. doi: