Small cell neuroendocrine carcinoma of the endometrium.

Ten cases of endometrial small cell neuroendocrine carcinoma are described. The ages of the patients ranged from 50 to 75 years (mean, 64 years). Most of the tumors were bulky, intraluminal masses that invaded at least half of the myometrial wall. Small cells were the only malignant element in two tumors. In the other eight, there were admixed elements of adenocarcinoma (five), adenosquamous carcinoma (two), or heterologous mesodermal mixed tumor (one). Histologic examination of metastatic deposits in six cases revealed solely small cells in all but one. Immunohistochemical evidence of neuroendocrine differentiation was demonstrated in all tumors using the markers chromogranin, synaptophysin, leu-7, or neuron-specific enolase. Six of these tumors were originally interpreted as mesodermal mixed tumors with a homologous, stromal-type sarcomatous component at initial pathologic examination, but were reclassified as carcinoma. Clinical follow-up of these 10 patients and an additional seven well-documented patients reported in the literature provided strong evidence for the aggressive nature of this neoplasm. Endometrial small cell neuroendocrine carcinoma is a rare, but aggressive neoplasm that can commonly be mistaken for a homologous-type mesodermal mixed tumor.