Epithelioid trophoblastic tumor: review of a rare neoplasm of the chorionic-type intermediate trophoblast.

We present a brief review of epithelioid trophoblastic tumor, a rare trophoblastic neoplasm derived from chorionic-type intermediate trophoblastic cells that typically presents in reproductive-age women between 1 and 18 years following a previous gestation. Histologic features include a nodular growth pattern of monomorphic, epithelioid cells within a hyaline matrix. Areas of necrosis and mitotic activity (0-9 mitoses per 10 high-power fields) are additional features of this neoplasm. Positive immunostaining for p63 and cytokeratin, frequent location in the lower uterine segment and endocervix, as well as the epithelioid appearance can lead to confusion with squamous cell carcinoma. Inhibin-alpha is typically expressed, as well as focal, more variable expression of other trophoblastic markers including beta-human chorionic gonadotropin, human placental lactogen, placental alkaline phosphate, and Mel-CAM (CD148). The clinical behavior of this rare form of gestational trophoblastic disease is difficult to predict. Although most cases follow a benign course following resection, there is a potential for metastatic disease.