Subsequent endometrial carcinoma with adjuvant tamoxifen treatment in Japanese breast cancer patients

This study aimed to detail the clinicopathologic features of endometrial carcinomas that developed in Japanese patients receiving adjuvant tamoxifen treatment for breast cancer patients. Ten endometrial carcinomas in tamoxifen-treated breast cancer patients were collected from two medical centers. The endometrial carcinomas included two stage Ia, four stage Ib, two stage Ic and two stage IIIc. Three tumors were Grade 1, six were Grade 2, and one was Grade 3. The tumor was limited to the endometrium in two cases. Myometrial invasion was limited to the inner half of the myometrium in five cases and involved the outer half in three. A mild degree of lymphovascular space invasion was identified in five cases. Deep cervical invasion was recognized in one case. The cell types comprised nine endometrioid adenocarcinomas and one serous carcinoma. Five of eight postmenopausal endometrial carcinomas were associated with polypoid endometrial lesions composed of cystically dilated atrophic and proliferative glands widely separated by fibrotic stroma. Two patients with retroperitoneal lymph node metastases died of endometrial cancer. One patient developed a contralateral breast cancer during tamoxifen treatment. No patient died of breast cancer. We did not demonstrate a higher frequency of either high-grade tumors or unfavorable histologic subtypes in tamoxifen-treated Japanese breast cancer patients.