An incidentally diagnosed epithelioid trophoblastic tumor in hysterectomy.

Epithelioid trophoblastic tumor is a rare non-molar gestational trophoblastic disease. A 40-year-old multiparous woman was incidentally diagnosed with epithelioid trophoblastic tumor after hysterectomy. Hysterectomy specimen revealed multiple small, tan to yellow nodules measuring 0.3-0.8 cm just below the endometrium. In the microscopic examination uniform neoplastic cells with varying cellularity were accompanied by necrotic zones and eosinophilic hyaline material. Immunohistochemically neoplastic cells were diffusely stained with CK 7, inhibin-alpha, p63, hPL, and CD146. There was no staining with beta-HCG, SMA, PLAP, or h-caldesmon. Ki-67 proliferative index was approximately 10% and cyclin E was stained in approximately 10% of the neoplastic cells. Although immunohistochemical studies are helpful in classifying gestational trophoblastic lesions, borderline values can cause diagnostic confusion between neoplastic and reactive lesions, particularly in inadequate endometrial biopsies.