Introduction: The morphological characteristics of the endometrium in patients with choriocarcinoma have not been well described. We described the endometrial morphology patterns in 46 choriocarcinomas and analyzed their relationship with the clinicopathological characteristics of these patients. Methods: Forty-six patients diagnosed with choriocarcinoma that had sufficient endometrial tissues for histopathological diagnosis were selected. Diagnoses of choriocarcinoma and secretory status of endometrium were reviewed. LHCGR expression of endometrium was evaluated by immunostaining. Results: Endometrial morphology was classified as secretory or nonsecretory. The 15 secretory specimens included 2 highly secretory and 13 common secretory specimens. The 31 nonsecretory patterns included 1 hyperplasia without atypia, 7 disordered proliferations, 13 typical proliferations, and 10 resting endometria. Among these, 11 specimens with overall nonsecretory patterns showed focally weak secretory changes surrounding the choriocarcinoma lesion. Secretory patterns were observed in classic choriocarcinomas (8/17) and monomorphic choriocarcinomas (7/21) but not in scanty-trophoblast choriocarcinomas (0/8). Secretory changes appeared significantly less frequently in patients who received multi-agent chemotherapy (4/25) than in those who did not (7/14) or received single-agent chemotherapy (4/7) (P = 0.030). The differences in age, months since the last pregnancy, pregnancy type, recurrence, specimen type, gross diameter, human chorionic gonadotropin (hCG) levels, and expression of hCG receptors were not statistically significant. Conclusions: The endometrial morphologies in choriocarcinoma were diverse, including various proliferative and secretory changes, but rarely hypersecretory changes, compared to the prevailing hypersecretory endometrium in hydatidiform moles. The variety in endometrial morphology was the consequence of ovarian hormonal disturbances of the hypothalamic-pituitary-gonadal axis by hCG from choriocarcinoma. Therefore, the endometrium may serve as a clue for histopathological diagnosis of choriocarcinoma. Our study presents the largest cohort reported to date to describe the diverse spectrum of endometrial changes in choriocarcinoma patients.
Keywords: choriocarcinoma; differential diagnosis; endometrium; human chorionic gonadotropin; luteinizing hormone/choriogonadotropin receptor.