Fibroepithelial lesions of the breast with pleomorphic stromal giant cells: a clinicopathologic study of 4 cases and review of the literature.

Pleomorphic stromal giant cells are occasionally found as an incidental finding in breast tissue but are only rarely seen in fibroepithelial lesions. In this report, we describe 4 fibroadenoma-like lesions of the breast with pleomorphic stromal giant cells. Two cases had focal stromal hypercellularity, one of which was with architectural features borderline between a fibroadenoma and a phyllodes tumor, but none was considered diagnostic of phyllodes tumor. One lesion had up to 4 mitotic figures per 10 high-power fields, including rare atypical mitotic figures. The remaining 3 cases lacked mitotic activity. Follow-up for 3 cases at 16 to 59 months revealed no evidence of tumor recurrence. The fourth case was lost to follow-up. It appears that the presence of pleomorphic stromal giant cells in an otherwise benign fibroepithelial lesion has no adverse clinical significance. The clinicopathologic features of each case are discussed, and a review of the literature is provided.