Unusual endometrial stromal cell changes mimicking metastatic carcinoma

We report an unusual histopathologic finding in the endometrium from six premenopausal or perimenopausal patients who underwent biopsy for abnormal uterine bleeding. In each case the endometrial stromal cells focally exhibited a pronounced epithelioid appearance; some showed a cord-like trabecular pattern and others a signet-ring-like cell change. All raised the possibility of a metastatic malignancy, particularly from the breast. The epithelioid appearance of the stromal cells appears to be an unusual artifact occurring in a background of secretory change and predecidualization with nonmenstrual breakdown.