CPT® Code 88365

In situ hybridization (FISH) is a sophisticated laboratory technique utilized to identify and localize specific nucleic acid sequences, including DNA and RNA, within fixed tissues or cells. This method provides critical temporal and spatial information regarding gene expression and genetic coding, which is essential for understanding the organization, regulation, and functional roles of genes within biological systems. The process begins with the fixation of sample cells or tissues, which preserves the target transcripts in their original locations. Following fixation, a DNA or RNA probe is introduced, which hybridizes, or binds, to the target nucleic acid sequence at an elevated temperature. After this binding occurs, any unbound excess probe is thoroughly washed away to ensure specificity. The remaining bound DNA or RNA targets are then stained using spectrally distinct fluorophore labels, allowing for visualization under fluorescent microscopy. This technique, known as FISH, can be employed to assess various genetic characteristics, such as gene presence, copy number, and location through DNA-FISH, or to analyze gene expression and the localization of RNA through RNA-FISH. Notably, FISH has the capability to utilize multiple probes simultaneously, enabling the visualization of co-locations of different targets within a single specimen. The CPT® Code 88365 specifically refers to the initial single probe stain procedure performed on a specimen, while additional single probe stains are reported using code 88364, and the use of multiple probes in the same staining procedure is captured by code 88366.