While formalin-fixed, paraffin-embedded (FFPE) tissue is preferred, IHC can be performed on frozen sections. Frozen sections may be used for more specialized studies, such as on lymph nodes or for thicker sections necessary for axon studies in nerve tissue. However, with the introduction and use of antigen unmasking and epitope retrieval methods, use of frozen sections for IHC is used less frequently. Frozen sections are primarily used when a quick evaluation is necessary without the delay of fixation, tissue processing, and slide processing.