Multinucleated stromal giant cells in mammary fibroepithelial neoplasms. A study of 11 patients.

Multinucleated stromal giant cells (MSGCs) found in otherwise-banal breast tissue have only rarely been mentioned in specific lesions. We describe unilateral fibroepithelial tumors with MSGCs in 11 women who were 23 to 60 years old (mean age, 42 years). The tumors ranged from 1.7 to 9.0 cm in greatest dimension (mean, 3.7 cm) and were classified on the basis of stromal cellularity, infiltration at the margin, cellular pleomorphism, and mitoses independently of MSGCs. Using these criteria, there were four fibroadenomas, one benign cystosarcoma, and four low-grade and two high-grade malignant cystosarcomas. The MSGCs had hyperchromatic or vesicular nuclei, many with clear nuclear inclusions. The nuclei were often arranged in a semicircular or florette pattern. The MSGCs, although widely distributed, tended to cluster. They accounted for most of the stromal cellularity in the fibroadenomas, numbering focally up to 10 per high-power field. The benign and low-grade malignant cystosarcomas had fewer MSGCs. The MSGCs contributed least to the cellularity in the high-grade cystosarcomas. Five patients had no further therapy. Five patients underwent wide excision and one patient had a mastectomy. Follow-up extended to 8 years (median follow-up, 4 years). There were no recurrences, and all patients were alive with no evidence of disease. The results of this study lead us to conclude that the diagnosis and grading of fibroepithelial tumors of the breast depend on the cellularity and pleomorphism of the stroma, exclusive of MSGCs. Cystosarcomas that have MSGCs do not have an especially malignant clinical course.