Immunohistochemistry utilization in autopsy pathology: a Canadian experience

Immunohistochemistry (IHC) is an important part of the diagnostic work-up in surgical pathology, but the use of IHC in autopsy pathology is poorly defined. We measured IHC utilization by pathologists performing 609 consecutive non-medicolegal, hospital-based, adult autopsies over a three-year period. IHC requests on non-neurologic and neurologic material were analyzed separately. Total stains, number of tissue blocks, specific antibody requests, resident trainee involvement, and ordering pathologist were recorded. For all autopsies on which IHC was requested, the final autopsy report was reviewed. IHC was requested on 345 cases (57%), and a total of 4612 stains were performed (mean 13.5 per autopsy). For non-neurologic autopsy tissues, IHC was used most commonly for the accurate diagnosis of malignancy. For neuropathologic autopsy examinations, IHC was employed most commonly to exclude neurodegenerative conditions and correlate ante-mortem clinical neurologic findings. Resident involvement did not significantly impact utilization. Individual pathologists demonstrated a wide variation in IHC utilization. We conclude that IHC is used extensively in Canadian non-medicolegal autopsy pathology reflecting the complexity, extent, and severity of disease in patients dying in a tertiary-care, academic hospital setting. Utilization is strongly influenced by the neuropathology component of these autopsies. The results provide a point of reference for IHC utilization in autopsy pathology.