High‐grade encapsulated papillary carcinoma of the breast: an under‐recognized entity

Aims Encapsulated papillary carcinoma ( EPC ) is a recognized special type of breast carcinoma. Despite compelling evidence indicating its invasive nature, although not of a conventional form, the current consensus is to manage EPC as an in‐situ disease, based on its indolent clinical behaviour. Although most EPC s are recognized to be of low and intermediate grade, a distinct proportion of these tumours do show high cytonuclear grade features. The existence and behaviour of these rare high‐grade variants remains to be defined. We aim to characterise these tumours and provide evidence to guide their management. Methods and results In this study, we have identified 12 high‐grade EPC s without associated conventional stromal invasion. To further characterize these high‐grade tumours, a series of invasive papillary carcinomas ( n = 30) were assessed for the coexistence of EPC . The literature was also reviewed. Approximately 3% of pure EPC s showed high‐grade features as defined by nuclear pleomorphism and increased mitotic activity. These tumours not only showed histological features associated with aggressive behaviour, but were also often hormone receptor‐negative, tended to be of larger size, and were more frequently associated with stromal invasion. Of the 10 patients with follow‐up data, one with pure high‐grade EPC developed recurrence and died of her disease. Conclusion High‐grade EPC is rare, and its histological features and more aggressive clinical behaviour suggest that consideration should be given to managing it in a similar fashion to conventional forms of invasive breast carcinoma, based on established clinicopathological parameters.