EPITHELIOID CELLS IN MYOID HAMARTOMA OF THE BREAST - A POTENTIAL DIAGNOSTIC PITFALL FOR CORE BIOPSIES

Objective.--We report six cases of myoid hamartoma of the breast, a ra re benign lesion in which the characteristic smooth muscle cells may h ave epithelioid histology. We emphasize the importance of radiographic correlation and immunohistochemical studies to diagnosis, particularl y on stereotactic core biopsies, to avoid potential confusion with inf iltrating lobular carcinoma. Design.--Case studies. Prospective and re trospective analysis of six cases, including stereotactic biopsy of tw o. Setting.--Academic medical center-based pathology practice. Patient s.--Six postmenopausal women, aged 50 to 59 years, with palpable or no npalpable mammographically evident breast masses. Results.--All the le sions were radiographically well circumscribed, most showing heterogen eous radiodensity. Histologically variable amounts of glandular, fibro us, and adipose tissue were admired with smooth muscle cells, which oc casionally had prominent epithelioid features. All the lesions' myoid cells stained for smooth muscle markers as well as steroid receptor pr oteins. Stereotactic core biopsy was diagnostic in one case, making ex cision unnecessary. Conclusions.--With proper radiographic correlation and immunohistochemical confirmation, myoid hamartoma can be confiden tly diagnosed even on the limited tissue samples yielded by stereotact ic core biopsy.