Fluorescence in situ hybridization on formalin-fixed, paraffin-embedded tissue sections.

Although in situ hybridization has been in use for over 30 years, its application to the study of solid tissue has only recently been adopted. Despite the numerous reports of the viability of formalin-fixed, paraffin-embedded (FFPE) tissue for fluorescence in situ hybridization (FISH) testing, this technique has not been universally implemented in the routine diagnostic setting. This is most likely due to the perception that the process is more technically demanding than FISH using conventional cytogenetic samples. FFPE FISH does, however, enable retrospective analysis of archived tissue samples and is helpful in the diagnosis of morphologically difficult cases such as Burkitt-like lymphoma, diffuse large B-cell lymphoma, and mantle-cell lymphoma.