Utility of fibronectin in immuocytochemial differentiation of reactive mesothelial cells from metastatic malignant cells in serous effusions.

Cytological evaluation of serous effusions often poses difficulties to the pathologists. This study was designed to assess the utility of fibronectin as a mesothelial cell marker and evaluate its use along with carcinoembryonic antigen (CEA) as a short panel to aid in the differentiation of reactive mesothelial cells from metastatic adenocarcinoma cells in serous effusions. Forty serous effusion cases from clinically benign cases and forty from clinically malignant cases with a known primary were included in the study. After routine cytological evaluation, the cases were categorized as benign, suspicious and malignant. All the cases were studied for fibronectin and CEA immunostaining using APAAP technique. In the present study, fibronectin emerged as a 100% specific and 93.4% sensitive marker for mesothelial cells. CEA immunostaining was seen in 80% cases of metastatic adenocarcinoma in serous effusions. Mesothelial cells did not show any CEA positivity. Short panel of CEA and fibronectin aided in reaching a correct diagnosis in three out of five cytologically suspicious cases.