Metastatic mucinous carcinomas in the ovary: a practical approach to diagnosis related to gross aspects and to immunohistochemical evaluation.

Ovarian mucinous carcinomas are uncommon, and the differential diagnosis is metastatic carcinoma mainly from the gastrointestinal tract. The aim was to verify the importance of immunohistochemical reactions and the algorithm described in literature on the basis of laterality and tumor size. Twenty-five cases identified as metastatic mucinous adenocarcinomas were reviewed, along with clinical records; a tissue microarray was created, and immunohistochemical reactions for CK7, CK20, Ca125, hormonal receptors, WT1, DPC4, β-catenin, and Cdx2 were determined. The median age was 51, and only 9 patients had a history of cancer. Sixteen patients (64%) had bilateral tumors, with sizes ranging from 5 to 36 cm (average, 20.5 cm); 9 (36%) had unilateral tumors varying from 5.5 to 38 cm (average, 21.8 cm). Algorithm agreement was 76%; most unilateral tumors were >13 cm. Common positive markers were Dpc4 (88%), Cdx2 (68%), CK20 (60%), and CK7 (44%). The useful markers were CK7, CK20, and Cdx2, although there were cases with overlapping results. The most common primary tumor was of colorectal origin (14 cases). The mean survival age was 32.6 mo. Although the proposed algorithm and immunohistochemical reactions are useful tools for diagnosis, some mucinous tumors cannot be definitively classified as primary or metastatic without further clinical evaluation, emphasizing the limits of this challenging diagnosis.