Ubaradka G. Sathyanarayana, PhD, Chandler Birch. Raymond B Nagle, MD, PhD, Scott A Tomlins, MD, PhD, Nallasivam Palanisamy, PhD, Wenjun Zhang, PhD, Antony Hubbard, Patrick Brunhoeber, MD, Yixin Wang, PhD, Lei Tang, PhD
Determination of optimum formalin fixation duration for prostate needle biopsies for Immunohistochemistry and Quantum dot FISH analysis
Ventana Medical Systems/Roche, Tucson, AZ and University of Michigan, Ann Arbor, MI
Abstract:
Prostate biopsy is the key clinical specimen for disease diagnosis. However, various conditions used during biopsy processing for histological analysis may affect the performance of diagnostic tests, such as hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC) or in situ hybridization (ISH). One such condition that may affect diagnostic test performance is fixation duration in 10% Neutral Buffered Formalin (NBF). For example, prostate needle biopsies are often less than 1 mm in diameter and thus over-fixed. It is important to understand the impact of tissue fixation duration on diagnostic test performance to enable optimized assay procedures. This study was designed to study the effect of 10% NBF fixation duration of prostate needle biopsy on multiplexed Quantum dot (QD) ISH assay of ERG and PTEN, two genes commonly altered in prostate cancer. The samples were also evaluated for H&E staining and ERG and PTEN IHC. H&E staining and ERG and PTEN IHC were acceptable for all the duration of fixation tested. For QD ISH, we observed good signal with biopsy samples fixed from 4 hr. to 120 hr. Biopsy specimens fixed between 8 hr. to 72 hr. gave the best signal as scored by the study pathologist. In a separate cohort of 18 routinely processed prostate biopsy cores, all cores were stained successfully with the QD ISH assay and results were 100% concordant to ERG and PTEN IHC. We conclude that 8 hr. to 72 hr. duration of fixation for prostate needle biopsies in 10% NBF results in optimal QD ISH assay performance.
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