MOC31 immunoreactivity in primary and metastatic carcinoma of the liver - Report of findings and review of other utilized markers

Differentiating between primary tumors of the liver and metastatic lesions can, at times, be difficult. Various histochemical and immunohistochemical methods have been used in an effort to better delineate between hepatocellu lar carcinoma (HCC), especially the microglandular variant, primary cholang iocarcinoma, and metastatic adenocarcinoma; these ancillary studies can yie ld less than satisfactory results. Recently, anti-MOC31, a monoclonal antib ody directed against a cell surface glycoprotein, has been shown to be help ful in distinguishing between adenocarcinoma and mesothelioma. This study a ddresses whether this antibody might be helpful in distinguishing between H CC, primary cholangiocarcinoma, and metastatic adenocarcinoma in the liver. Formalin-fixed, paraffin-embedded tissue sections from 15 HCC (including 1 0 microglandular variants), 14 primary cholangiocarcinomas, and 33 metastat ic adenocarcinomas (7 colon, 1 lung, 8 breast, 4 GE jct/gastric, 9 pancreas , 2 small intestine, 1 renal 1 ovary) were immunostained with anti-MOC31 (1 :40, Dako) after protease digestion and biotin block using a modified ABC t echnique. Positive staining was limited to membrane based reactivity; contr ols stained appropriately. Immunoreactivity for MOC31 was observed in 14 of 14 cholangiocarcinomas and 33 of 33 metastatic tumors. Staining was diffus e, intense, and readily interpretable, with rare exceptions. All 15 cases o f HCC were negative. We conclude that cholangiocarcinoma and metastatic ade nocarcinoma from a variety of sites express MOC31: HCC is uniformly negativ e for this marker. Anti-MOC31 may prove useful in the evaluation of liver n eoplasms where primary hepatocellular and adenocarcinoma enter the differen tial diagnosis; it is not useful in separating primary cholangiocarcinoma f rom metastatic adenocarcinoma.