Diagnostic frozen prostate sextant biopsies: an approach for preserving protein and RNA for additional studies

Primary prostate cancer represents 29% of newly diagnosed visceral cancers in men. Despite this common occurrence, relatively little is known about the pathogenesis of this malignancy. High-grade prostatic intraepithelial neoplasia (HGPIN) is generally accepted as a precursor to invasive prostate carcinoma. There is a lack of adequate animal models, and the available cell culture lines are limited. Tissue from prostate needle core biopsies that have been frozen can provide adequate material for both diagnosis and research.

Transrectal sextant needle biopsies were snap-frozen, serially sectioned and alternately stained with hematoxylin-eosin or reacted with a basal cell-specific antibody. Two pathologists examined all of the sections, which were scored for the presence or absence of carcinoma and HGPIN. Portions of the remaining tissue were used for studies of protein expression and gene expression.

The incidence of carcinoma was 39%, comparable to the mean percent positive cases reported using conventional fixation and paraffin embedding. The incidence of HGPIN was 33%, higher than previously reported.

Prostate carcinoma can be accurately diagnosed using frozen material. The observed high frequency of HGPIN is attributed to the instability of nuclear structure in the frozen material of the atypical nuclei, resulting in inflated grading of PIN lesions. Sufficient material remained in the frozen blocks for additional studies of protein and gene expression.