Phyllodes tumours of the breast - differentiating features in core needle biopsy

Aims: To investigate the usefulness of histological features in the differentiation of fibroepithelial lesions of the breast (phyllodes tumours and fibroadenomas) in core needle biopsies. Methods and results: Forty-nine and 69 excision-proven core biopsies of phyllodes tumours and fibroadenomas, respectively, were evaluated histologically for stromal cellular changes (overall stromal cellularity, variability in stromal cellularity, stromal cell pleomorphism, and mitotic count) and stromal architectural changes (stromal overgrowth, fragmentation of the cores, and fat in stroma). In core needle biopsies of phyllodes tumours, overall stromal cellularity, stromal cell pleomorphism and mitotic count showed good correlation with excisions. In phyllodes tumours, core needle biopsy diagnosis showed increased certainty with increasing degree of malignancy. Core biopsies of phyllodes tumours showed more consistent stromal cellular changes (overall stromal cellularity, variability in stromal cellularity, stromal pleomorphism, and mitotic count) than those of fibroadenomas. These parameters were also useful for differentiation between benign and malignant fibroepithelial lesions. For grading phyllodes tumours, stromal cell pleomorphism and mitotic activity were found to be helpful. Conclusions: In the core biopsy assessment of phyllodes tumours, evaluation of selected histological parameters, particularly those pertaining to stromal cellular changes, is helpful.