OBJECTIVETo study the clinicopathologic features, immunophenotype, differential diagnosis and prognosis of uterine epithelioid trophoblastic tumor(ETT).

METHODSFrom 2000 to 2007, 5 ETTs cases were diagnosed in the affiliated Women's Hospital, School of Medicine, Zhejiang University. The pathologic characteristics and immunophenotype of the tumors were analyzed by histological examination and immunohistochemistry of CK18, p63, inhibin-alpha, HCG, HPL, PLAP and Ki-67. The clinical prognostic factors were evaluated based on a following-up data with a period of 11 - 50 months.

RESULTSThe overall prevalence of ETT was 0.48% among all the gestational trophoblastic diseases patients received in the same period. Five ETT patients were in the reproductive ages with a median of 33 years. Histologically, the tumor showed an invasive, nodular growth consisting of uniform mononuclear trophoblastic cells. There were zones of hyaline material in the tumour nests. Necrosis was commonly seen with a characteristic geographic pattern. Immunohistochemically, all cases displayed a diffuse CK18 and p63 positivity, to be either positive focally or negative for HCG, HPL and PLAP staining. Inhibin-alpha staining was positive or negative either in the 5 cases. Two patients died of the tumour relapse: one died after 1 year with the tumor having a high mitotic activity (averagely 15 mitotic figures per 10 high-power fields), and the other died of lung metastasis 2 years after the diagnosis.

CONCLUSIONSETT is a rare trophoblastic disease with distinct clinicopathological features and immunostaining patterns. A high mitotic index and lung metastasis are indicators for an unfavorable prognosis.