Recent advances in the pathology of fibroepithelial tumours of the breast

Fibroepithelial lesions of the breast are biphasic lesions with epithelial and stromal components, as exemplified by fibroadenoma and phyllodes tumour. Fibroadenomas are benign, but a subset of complex fibroadenoma is associated with slightly increased long-term cancer risk. Phyllodes tumour is characterised by a leaf-like pattern arising from stromal expansion. It shows a variable degree of malignancy, with a potential for recurrence or metastasis. Conventionally, histological parameters of stromal cellularity, nuclear pleomorphism, overgrowth, mitotic activity and margin configuration are used for grading, but no definitive criteria have been identified to predict the behaviour. Other markers that have been investigated so far include p53, hormonal receptors, proliferation markers, angiogenesis, c-kit (CD117) and CD10 (CALLA), all without clear-cut advantage over histological criteria. There is also emerging histological and molecular evidence that fibroadenoma and phyllodes tumour may be related and epithelial–stromal interaction may play a role in the pathogenesis of these fibroepithelial lesions.