Ovarian hilus cell heterotopia.

The eutopic location of ovarian hilus cells in the hilar stroma of the ovary and in the adjacent mesovarium is widely recognized. Hilus cell heterotopia, that is, the presence of normal hilus cells in an abnormal site, is rare and there are only a few case reports and 1 earlier systematic study of this phenomenon in the literature. Hilus cell heterotopia has been reported in the fimbrial stroma of the fallopian tube, paratubal and parafimbrial cyst walls and usually takes the form of discrete, circumscribed nodules or clusters of hilus cells. We report a series of 6 cases of hilus cell heterotopia, all of which were identified in association with other underlying pelvic pathology and in patients over 40 years of age. We have shown that hilus cell heterotopia is not limited to the fallopian tube but can also involve the subcapsular ovarian cortex and may have an infiltrative (rather than a nested) growth pattern that can resemble metastatic carcinoma, potentially mimicking a metastatic lobular carcinoma of the breast. This is particularly relevant in patients in whom staging procedures are carried out for gynecologic pelvic neoplasms, and for those few patients who also have a history of concurrent carcinoma, particularly of the breast.