Abstract

This study aimed to document chronologic histologic changes of endometrial biopsies from patients with endometrial adenocarcinoma on high-dose progestin therapy. Seven patients with presumptive FIGO stage IA endometrial adenocarcinoma treated with medroxyprogesterone acetate 600 mg/day were investigated retrospectively. Good response was defined as complete disappearance of carcinoma foci within 16 weeks of treatment and poor response as the presence of residual foci at 16 weeks. Two patients were poor responders and were excluded from the study, while five good responders were analyzed. Hematoxylin and eosin (H&E)–stained slides were reviewed and analyzed based on nine histologic features to describe the histology observed commonly in good responders. All the five good responders showed relatively uniform morphologic changes during the high-dose progestin therapy and the common histology was described as follows. The first change was swelling of the neoplastic glandular epithelial cells with pale vacuolated cytoplasm and round to oval nuclei. Mitotic arrest was also observed. Next, the epithelia were disrupted by lymphoplasmocytic infiltration and replaced by low cuboidal epithelium with or without squamous or morular metaplasia. The stromal area increased with predecidual changes. The final morphology was small atrophic glands scattered in predecidual stroma with dilated vessels. Therefore, the morphologic change of the endometrial biopsy observed in earlier stage of treatment might be able to predict good response to high-dose progestin therapy.