Amelanotic malignant melanoma of the esophagus: case report and review of the literature.

A case of amelanotic malignant melanoma of the esophagus in a 76-year-old woman is reported. A whitish polypoid tumor, measuring 3 x 2 x 2.7 cm, surrounded by black pigmented mucosa, was detected in the middle intrathoracic esophagus. The tumor showed a lobulated surface lined by squamous cell layer, and had epithelioid and polyhedral cells forming alveolar clusters. Melanin pigments or stainability for the dihydroxyphenylalanine (DOPA) reaction were only observed in a few tumor cells. Junctional changes and mucosal melanosis, however, were found freely in the mucosa around the tumor. Many tumor cells showed a strongly positive immunohistochemical reaction for neuron specific enolase (NSE) and S100 protein. The patient died of widespread metastases six months after surgery. Further, a review of 106 reported cases of primary esophageal malignant melanoma, including 29 autopsies, was made; the melanomas were found to include 10 of amelanotic type, eight of which had been misdiagnosed at biopsy. Junctional changes could be found in the mucosa over or around the tumor, in four cases, and mucosal melanosis in one. Lymph node metastasis was the most frequently observed development at autopsy regardless of whether the tumor was amelanotic or melanotic. For correct diagnoses of melanomas of the amelanotic type, peripheral mucosal findings, such as junctional changes or melanosis, should be helpful; and, in order to obtain a good prognosis, a careful resection of the regional lymph nodes could prove valuable.