[1031] Utility of Phosphotungstic Acid Haematoxylin (PTAH) in the Differentiation of Renal Epithelial Tumors

John K Schoolmeester, William R Sukov, John C Cheville. Mayo Clinic, Rochester, MN

Background: Proper histologic classification of renal cell carcinoma is critical as its subtypes demonstrate significant variation in their prognosis. Oncocytoma, a benign lesion, may show morphologic overlap with chromophobe (CHRCC), papillary (PRCC) and clear cell (CCRCC) renal cell carcinoma. Immunohistochemistry (IHC) can be helpful in differentiation of these lesions but can also lead to equivocal results. We evaluated the use of phosphotungstic acid haematoxylin (PTAH), a histochemical stain, in the differentiation PRCC, CCRCC, CHRCC and oncocytoma and compared these results to established IHC stains.
Design: Twenty-five cases of CHRCC, PRCC, CCRCC and oncocytoma were each used for tissue microarray construction consisting of 4 cores per tumor (0.6 mm diameter). All 100 cores were stained with PTAH, CD117, AMACAR, CK7 and eCadherin. Each core was semiqualitatively graded as strong (2+), weak (1+) or none (0) and semiquantitatively graded as diffuse (>50%), intermediate (26-50%) or focal (1-25%). Staining of at least 1+, intermediate and greater was considered positive.
Results: Staining results are summarized in Table 1. PTAH created unique patterns in all 4 tumor types. Oncocytoma demonstrated diffuse, uniformly strong cytoplasmic staining (Figure A); CHRCC showed dusty, weak cytoplasmic stain in variable quantities of cells (Figure B); PRCC exhibited either a basilar cytoplasmic distribution with apical clearing (Figure C) or rarely diffuse cytoplasmic staining similar to oncocytoma; CCRCC featured mostly a lack of staining (Figure D).

Conclusions: Our study shows that the unique staining pattern of PTAH consistently distinguished oncocytoma from CHRCC and is of greater utility than IHC in this respect. In conjunction with tumor morphology, PTAH stratified all tested subtypes of RCC more accurately and reliably than IHC. We believe PTAH is of exceptional use in differentiation of oncocytoma, CHRCC, PRCC and CCRCC.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 155, Monday Morning


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