Mucinous cystadenocarcinoma of the breast: a case report of a rare entity and how to recognize it

Abstract

Mammary mucinous cystadenocarcinoma is a rare primary breast malignancy. First described in 1998 by Koenig and Tavassoli, it was named in the third edition of the WHO International Classification of Tumours (2003) but was only recognized as a distinct entity in the most recent fifth edition (2019). Lack of data impedes our understanding of tumourigenesis and long-term prognosis. No standardized treatment protocol is available. Here we present a case in which this unusual diagnosis was suggested on core biopsy and confirmed on surgical resection. The purpose of this case report is to add to the data on its long-term behaviour, and illustrate an approach to its diagnosis.