Clinicopathologic Analysis of Postchemotherapy Gestational Trophoblastic Neoplasia: An Entity Overlapping With Epithelioid Trophoblastic Tumor.

Surgery is generally not required for the majority of gestational trophoblastic neoplasias (GTNs) because they are potentially curable by chemotherapy alone. The histologic assessment is rarely available although the identification of a specific subtype of GTN is relevant to clinical intervention and prognostic prediction. In this study, we analyzed the clinicopathologic features of 4 postchemotherapy GTNs. They presented as a persistent uterine (Cases 1, 2, and 3) or pelvic mass (Case 4) with a raised serum β-hCG level after multiple courses of chemotherapy. All patients were alive without evidence of disease at follow-up periods of 58 to 109 mo after surgery and salvage chemotherapy except for Case 4 which had a recurrent pelvic mass. These GTNs had a characteristic histopathologic pattern of extensive necrosis and a rim of scant viable mononucleated tumor cells at the periphery of the lesion. Immunostaining showed that these tumor cells had a lower Ki67 index than choriocarcinoma, and epithelioid trophoblastic cell tumor although they exhibited an epithelioid trophoblastic cell tumor-like immunostaining pattern (CD146, hPL, and p63). A small number of β-hCG-positive multinucleated trophoblastic cells were also present in 3 of the 4 cases. We suggest that these postchemotherapy GTNs may represent a "snap shot" of the hypothetical choriocarcinoma-epithelioid trophoblastic cell tumor transition. Our findings should provide insights into the pathogenesis of GTNs.