Malignant amelanotic melanoma of the pleura without primary skin lesion:an autopsy case report.

Melanoma metastasizing to the lungs is common, but primary pulmonary or pleural melanoma is extremely rare. We present an autopsy case of malignant melanoma of the pleura without primary skin lesion in a 49-year-old man. A mass found in the right chest was diagnosed as spindle cell sarcoma by antemortem fine-needle aspiration cytology. At autopsy, a yellow-white tumor located primarily in the right visceral pleura (diagnosed as an amelanotic melanoma) was found to have invaded into the right lung, right parietal pleura, and right diaphragm, and to have metastasized into the left lung and visceral pleura, thyroid, and left adrenal gland. No primary site was found. The tumor cells were positive for S100 and focally positive for HMB-45, but negative for other markers. Immuno-histochemical examination for S100 and HMB-45 would thus appear to be useful for the diagnosis of an amelanotic melanoma.