The 4 present cases with endometrioid adenocarcinoma (EMA) of the ovary were characterized by estrogen overproduction and resemblance to sex cord-stromal tumor (SCST). The patients were all postmenopausal, at ages ranging from 60 to 79 years (av. 67.5), who complained of abdominal discomfort or distention and also atypical genital bleeding. Cytologically, maturation of the cervicovaginal squamous epithelium and active endometrial proliferation were detected. The serum estrogen (estradiol, E2) value was preoperatively found to be elevated, ranging from 48.7 to 83.0 pg/mL (av. 58.4). In contrast, follicle stimulating hormone was suppressed to below the normal value. MR imaging diagnoses included SCSTs such as granulosa cell tumor or thecoma for 3 cases because of predominantly solid growth, and epithelial malignancy for one case because of cystic and solid structure. Grossly, the solid part of 3 cases was homogeneously yellow in color. Histologically, varying amounts of tumor components were arranged in solid nests, hollow tubules, cord-like strands and cribriform-like nests in addition to the conventional EMA histology. In summary, postmenopausal ovarian solid tumors with the estrogenic manifestations tend to be preoperatively diagnosed as SCST. Due to this, in the histological diagnosis, this variant of ovarian EMA may be challenging and misdiagnosed as SCST because of its wide range in morphology.