[910] Diagnostic Utility of ΔNp63 (p40) Immunostain in Prostatic Pathology

Muhammad T Idrees, Sunil Badve. IU School of Medicine, Indianapolis, IN

Background: Immunohistochemistry (IHC) plays an extremely important role in the diagnosis of prostatic adenocarcinoma (PA). Few markers have the sensitivity and specificity required for clinical usage. The absence of basal cells, a key diagnostic feature, has been exploited by using IHC markers specific to basal cells. p63, the most common of these markers, is successfully used in routine practice. However, p63 has 2 major classes of isoforms and currently available antibodies do not distinguish these isoforms. A novel antibody that specifically recognizes ΔNp63 isoform, also called p40, was evaluated for its specificity and specificity as a basal cell marker in prostate pathology, and a comparative analysis with p63 was performed.
Design: We selected 82 biopsy cases of PA (29, 25, and 28 with predominant patterns 3, 4, and 5, respectively) including 12 cases with prostatic intraepithelial neoplasia (PIN); we also included 33 benign cases (10 nodular hyperplasia, 5 basal cell hyperplasia, and 18 atrophy/partial atrophy) for analysis. Sections were incubated with p40 antibody (1:1000; Biocare Medical) after antigen retrieval (with high pH buffer) and IHC performed using the DAKO Flex system. p63 (clone 4A4; 1:400; Biocare Medical) immunostaining was performed in a similar manner. All slides were evaluated by both pathologists for the expression of p63 and ΔNp63 (p40) in the basal cells; a comparative analysis was also performed.
Results: Expression of p40 in normal prostate was restricted to basal cells; no expression in the luminal epithelial cells. In cases of PA, p40 immunostain was restricted to the basal cells in normal glands. Tumor cells did not exhibit any staining, irrespective of the Gleason pattern. This pattern of staining was identical to that seen with p63 immunostain. Both immunostains identified a discontinuous and patchy distribution of the basal cells in PINs. In benign cases, basal cells were clearly delineated in a continuous uninterrupted fashion by both immunostains. Atrophic and partial atrophy cases showed interrupted basal cell layer by both markers in all the cases and greatly facilitated the diagnosis. On comparison, the only difference in immunostaining identified was stronger staining intensity and associated ease of use with the p63 antibody.
Conclusions: The expression of ΔNp63 (p40) is restricted to basal cells of the prostate. Comparative analysis showed both p63 and p40 antibodies equally sensitive and specific for basal cells in both benign and malignant conditions. p40 immunostain can be used in prostate pathology as an alternative to p63 without loss of diagnostic accuracy.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 141, Wednesday Afternoon


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