Cytologic presentation and clinicopathologic correlation of Mullerian carcinosarcoma on serous fluid samples

Limited data are present to study the cytologic findings of Mullerian carcinosarcoma (MCS) in serous fluid samples and clinicopathologic features that are associated with cytology yield.

We studied 30 MCS patients diagnosed on surgical resection samples, and reviewed their cytomorphology and immunophenotypes on concurrent serous fluid cytology samples. Clinicopathologic features were also compared between cases with positive or negative cytology.

Fourteen out of 30 patients showed positive cytology, including 12 patients with only carcinomatous components and 2 with sarcomatous cells. Cytomorphology of MCS was mostly consistent with adenocarcinoma, with psammoma bodies occasionally present. The 2 cases with sarcomatous cells showed spindle cells without signs of heterologous differentiation. PAX8 was positive in 10 of 11 cases, and WT1 was positive in 8 of 11 cases including the case with negative PAX8. In 1 case, PAX8 and WT1 were only positive in the sarcomatous but not in carcinomatous cells. MOC31 showed consistent positivity in carcinomatous cells, which appeared to be more sensitive than B72.3 (positive in 72.7%). In addition, sarcomatous cells showed CD10 positivity in 1 case. Clinically, patients who developed body cavity effusions or with higher stage diseases were more likely to have positive cytology.

Cytologic diagnosis of MCS in the serous fluid is challenging due to the rare presence of sarcomatous component. Staining both PAX8 and WT1 is recommended to confirm their Mullerian origin, although both markers may be positive only in sarcomatous cells. Cytology yield of MCS is highly associated with the disease stage.