Fibroadenoma versus phyllodes tumor: a vexing problem revisited

Background Fibroepithelial lesions of the breast include fibroadenoma (FA) and phyllodes tumor (PT). Fibroadenomas are benign while phyllodes tumor range from benign, indolent neoplasms to malignant tumors capable of distant metastasis. Our study was to determine the select cytologic features that can accurately distinguish FA from PT. Methods A retrospective review was performed of patients who had histopathology follow up of FA or PT and on whom a pre-operative fine needle aspiration was performed. Cytologic criteria i.e. epithelial component, stromal component and background cellularity were assessed. Results 46 FA and 24 PT were specimens were reviewed. Median age and tumor size for FA and PT were 23.0 and 39.0 years, and 2.0 and 5.0 cm, respectively. Univariate analysis and regression models based on generalized estimating equations revealed that large opened out, folded epithelial sheets, frayed and irregular stromal fragment contours, spindle stromal cell nuclei, spindle cell nuclei in the background and background cell atypia are significant cytological predictors of PT. The GEE regression model achieved 78.9% diagnostic accuracy (p < 0.001) in identifying PT based on cytological features. Median epithelial: stromal ratio was 3.4 and 2.6 for FA and PT, respectively. Conclusion Presence of large, opened out, folded epithelial sheets, frayed and irregular stromal contours with spindle nuclei, background spindle cells and atypia can help distinguish PT from FA.