Intestinal-type mucinous ovarian carcinoma arising from a seromucinous precursor lesion

Objective: Mucinous ovarian carcinoma is a tumor with gastrointestinal differentiation, which is not associated with endometrial-type (endometriotic or seromucinous) precursors. Here, we describe a peculiar case of mucinous ovarian tumor with intestinal differentiation arising in a seromucinous lesion, which may represent a distinct entity. Case presentation: A 58-year woman underwent surgery due to a 14.5-cm ovarian mass with lymph nodal, peritoneal, omental and colorectal involvement. Histological examination with ancillary immunohistochemical analysis has been performed. Histologically, the mass was a carcinoma with intestinal differentiation and expansile growth pattern, arising in a seromucinous cystadenoma with intestinal metaplasia. Both the carcinoma and the metaplasia showed loss of Müllerian markers (estrogen and progesterone receptors, PAX8) and positivity for intestinal-type markers (cytokeratin 20, CDX2). Conclusions: Our case may represent the ovarian counterpart of endometrial gastrointestinal-type carcinoma, which is an aggressive entity developing from gastrointestinal metaplasia of the endometrial epithelium. Acknowledging the existence of such entity might be relevant in terms of diagnosis and patient management.