Stromal neoplasms of the breast: a comparative flow cytometric study.

We analyzed 42 mammary spindle cell neoplasms (10 conventional fibroadenomas, 8 giant fibroadenomas, 17 cystosarcoma phyllodes, and 7 stromal sarcomas) by flow cytometry to assess the diagnostic and prognostic relevance of DNA content analysis in the pathologic evaluation of these lesions. Our data indicate that all fibroadenomas were diploid, cystosarcoma phyllodes displayed diploid and aneuploid DNA content irrespective of their histological categorization, and that stromal sarcomas were all aneuploid and clinically aggressive. Diploid cystosarcoma phyllodes were biologically indolent, whereas most of the aneuploid neoplasms killed their hosts (P = 0.03). The present study indicates that a DNA content abnormality it is a reliable marker of malignancy in these neoplasms, and it may identify subsets of patients with variable biologic courses within the histopathologic spectrum of cystosarcoma phyllodes.