MOC-31, also known as Epithelial
specific Antigen/Ep-CAM, consists of two 34 and 39 kDa glycoproteins. These
glycoproteins are located on the cell membrane surface and in the cytoplasm of
virtually all epithelial cells with the exception of most squamous epithelia,
hepatocytes, renal proximal tubular cells, gastric parietal cells
and myoepithelial cells. MOC-31 is used in a panel of antibodies as a
negative marker for mesothelioma; and a negative stain for MOC-31 has been shown
to exclude lung adenocarcinoma. MOC-31 is useful in differentiating tumors of
unknown origin in liver cancers and distinguishing cholangiocarcinoma (+) from
hepatocellular carcinomas (-). MOC-31 may be advantageous in the
demonstration of epithelial cell differentiation in cases where
anti-cytokeratins are not clearly positive or in cases where a false positivity
for cytokeratin cannot be excluded, such as in submesothelial
cells.