Benign phyllodes tumour vs fibroadenoma: FNA cytological differentiation

The differential diagnosis of fibroadenomas vs phyliodes tumours by fine ne edle aspiration (FNA) cytology is not possible in the majority of cases. Th e present study aims to look at common and dissimilar features to allow dif ferentiation, if possible. We reviewed the FNA findings of 18 histologicall y proven phyllodes tumours and 18 fibroadenomas, checking in each case the epithelial features, the stromal features, and any atypia. Using a semi-qua ntitative score assessed by two observers we were able in most cases to dis tinguish a phyllodes tumour from a fibroadenoma. The most important criteri a were larger stromal fragments, numerous plump stromal bare nuclei, and th e higher ratio of stromal bare nuclei to epithelial bare nuclei in phyllode s tumours. In the present study, an original diagnosis of phyllodes tumour was made in 7/18 (38.9%) cases but with our criteria this could be improved to 15/18 (83.3%) cases. Therefore, the presence of specific stromal featur es in a dimorphic cellular pattern should suggest the correct diagnosis and differentiate its appearance from a cellular fibroadenoma.