Epithelial carcinomas arising within phyllodes tumours of the breast: a review of their histopathological, pathophysiological and molecular characteristics

Epithelial proliferation is a common feature of phyllodes tumours (PT) but epithelial malignancy is rare. This review seeks to further our understanding of epithelial malignancy within phyllodes tumours by analysing their histopathological and molecular characteristics in previously reported cases in the literature. PubMed was searched for case reports, case series and literature reviews of in situ and invasive carcinoma within phyllodes tumours. Only cases where the carcinoma was within the PT were included. Cases of synchronous carcinoma in the ipsilateral or contralateral breast were excluded. Eighty-six cases of in situ or invasive carcinoma within a PT were identified. Across the grades of phyllodes tumours there was a similar proportion of invasive carcinomas compared to in situ lesions. The malignant stroma correlates with a higher likelihood of epithelial malignancy, and molecular studies support a possible causal pathophysiological relationship. Malignant phyllodes tumours as compared to benign appear to have a greater likelihood to contain either an in-situ or invasive epithelial malignancy. This higher likelihood suggests that interactions between the malignant stroma and the transforming epithelium may play a significant role in the phenomenon which remains to be elucidated.