Immunoreactive secretory component of IgA in human tissues and tumors

Secretory component (SC) of IgA is known to be produced by many glandular epithelial cells. To assess the usefulness of this antigen as a glandular tumor differentiation marker, the authors evaluated its normal body distribution and tested a variety of glandular neoplasms. The known normal distribution of SC was confirmed and extended to include the prostate. Immunoreactive SC was detected only in epithelial and glandular tumors. Many types of well-differentiated adenocarcinomas, (ovary, prostate, small bowel, pancreas, stomach, biliary) however, contained little or no immunoreactive SC. Therefore, the authors conclude that immunoreactive SC cannot be used as a general differentiation marker in tumors of glandular derivation. A high frequency of antigenic expression was found in adenocarcinomas of the lung (4/10), breast (5/10), and colon (24/27). No correlation between expression and tumor differentiation was observed in pulmonary or mammary tumors. Only in colonic neoplasia was such a relationship detected. SC expression in colonic tumors was not related to mucin content but was associated with the presence of a visible brush border.