Immunohistologic heterogeneity of malignant tumors

Intratumor heterogeneity exists in most, if not all, human solid tumors and is reflected by differences in morphology, antigenicity, chromosomal and biochemical markers, invasion, metastatic spread, as well as sensitivity to therapy. Heterogeneity may be the result of genetic and/or environmental mechanisms. To be assessed by immunohistochemistry, heterogeneity of tumor cells has to be expressed by antigenic changes, i.e. quantitative or qualitative differences in antigen expression, secretion or uptake. Consequently, presence and distribution of hormones, steroid hormone receptors (e.g., in mammary carcinomas), blood group antigens (e.g., in diverse carcinomas), and cytoskeletal components, particularly intermediate filament-associated proteins (e.g., in neoplasms of diverse origin), can indicate heterogeneity within a tumor.