Immunohistochemical analysis of human embryos and fetuses: an insight into the mechanism of subversion of antigenic differentiation in neoplasia.

OBJECTIVES

Immunohistochemical identification of intermediate filaments and other cell identity markers is of immense value in diagnostic tumor pathology. However, the literature contains many examples of inappropriate expression of markers by various tumors or coexpression of two or more markers supposedly specific for different cell types. The present study investigated this subversion of antigen differentiation in tumors by using developing tissues as a model.

MATERIALS AND METHODS

Twenty-five human embryos and fetuses of 4 to 24 weeks' gestation were studied. An indirect immunoperoxidase method was applied to formalin-fixed, paraffin-embedded sections using a panel of 13 commonly used cell identity markers including intermediate filaments.

RESULTS

During early development, vimentin was found to be coexpressed with cytokeratin in surface ectoderm, developing notochord, renal tubule epithelium, and intestinal mucosa. It coexpressed with glial fibrillary acidic protein in developing neuroglial tissue, with S100 in cartilage, and with skeletal muscle markers in myotubules. Hence, vimentin represents immaturity of tissues and is coexpressed with specific cell markers to be eventually replaced by the latter. Transbarrier expression of cytokeratin in smooth muscle was also noted.

CONCLUSION

The aberrant expression of antigens in neoplastic tissues, as reported in the literature, simulates the varying expression of antigens in immature tissues during development. Hence, it is proposed that the phenomenon of antigenic subversion in neoplasia is related to the process of maturation and differentiation.