Immunohistochemistry (IHC) is important for cytology but poses special challenges because preanalytic conditions may differ from the conditions of IHC-positive controls.
To broadly survey cytology laboratories to quantify preanalytic platforms for cytology IHC and identify problems with particular platforms or antigens. To discover how validation guidelines for HER2 testing have affected cytology.
A voluntary survey of cytology IHC practices was sent to 1899 cytology laboratories participating in the College of American Pathologists Nongynecologic Cytopathology Education Program in the fall of 2009.
A total of 818 laboratories (43%) responded to the survey by April 2010. Three hundred fourty-five of 791 respondents (44%) performed IHC on cytology specimens. Seventeen different fixation and processing platforms prior to antibody reaction were reported. A total of 59.2% of laboratories reported differences between the platforms for cytology specimens and positive controls, but most (155 of 184; 84%) did not alter antibody dilutions or antigen retrieval for cytology IHC. When asked to name 2 antibodies for which staining conditions differed between cytology and surgical samples, there were 18 responses listing 14 antibodies. A total of 30.6% of laboratories performing IHC offered HER2 testing before publication of the 2007 College of American Pathologists/American Society of Clinical Oncologists guidelines, compared with 33.6% afterward, with increased performance of testing by reference laboratories. Three laboratories validated a nonformalin HER2 platform.
The platforms for cytology IHC and positive controls differ for most laboratories, yet conditions are uncommonly adjusted for cytology specimens. Except for the unsuitability of air-dried smears for HER2 testing, the survey did not reveal evidence of systematic problems with any antibody or platform.