Immunohistochemical evaluation of prostate needle biopsies using saved interval sections vs new recut sections from the block: a prospective comparison.

The best method of tissue sampling for performance of immunohistochemistry on prostate needle biopsy tissue sections has not been established. The aim of this study was to prospectively compare the usefulness of using saved interval sections vs new recut sections from the paraffin block in the immunohistochemical evaluation of prostate needle biopsy (PNB) material. Seventy (10.3%) of 682 PNB specimens consecutively examined over a 1-year period were evaluated immunohistochemically. Of these cases, 38 were concurrently evaluated using saved interval sections (2 levels) and recut sections. Identical staining results were achieved in 21 cases (55%). Loss of the atypical/ malignant focus of interest was seen in 3 (8%) of the interval sections vs 19 (50%) of the recut sections (P < .0001). The mean linear extent of the foci that were lost in the recut sections (0.75 mm) was significantly less than that of the foci that were not lost in the recuts (1.32 mm; P = .025). Fifteen (79%) of the 19 foci that were lost in the recut sections were 1 mm or less in length vs 7 (37%) of the 19 not lost in the recuts (P = .021). These findings support the practice of cutting and saving 2 interval levels of unstained sections of PNB specimens for potential immunohistochemical evaluation.