Clinical significance of in situ hybridization.

In situ hybridization is a morphologic method of localizing specific DNA or RNA sequences at the individual cell level. The technique can be applied to frozen or fixed tissues and cytologic preparations; various types of probes can be utilized and the reaction can be visualized by autoradiography using isotopic markers or by colorimetric methods. In the field of endocrinology, in situ hybridization has seen numerous applications; the detection of viral infections, the characterization of tumors with markers of endocrine differentiation, the determination of hormone synthesis by normal cells and neoplasms. Ectopic hormone production and the production of other substances such as growth factors and cytokines have been established using this new methodology and it has been used to examine production of specific receptors by individual cells in many endocrine tissues. The data that have emerged allow structure-function correlations that have not previously been possible using molecular techniques that are applied to homogenized tissues or even using the most sophisticated morphologic methods such as immunohistochemistry and electron microscopy.