[974] Oncocytic Papillary Renal Cell Carcinomas Should Be Classified Separately from Type 1 and Type 2 Tumors

Yunchuan D Mo, Stephen H Culp, Mairo L Diolombi, Helen P Cathro. University of Virginia, Charlottesville, VA

Background: Over the past decade, pathologists have increasingly recognized an oncocytic variant of papillary renal cell carcinoma (PRC) that complicates classification as Type 1 or Type 2 PRC. The International Society of Urological Pathology recently proposed reclassifying oncocytic papillary renal cell carcinoma (OPRC) as a separate subtype. We set out to test the validity of separating oncocytic tumors from other PRC.
Design: This study examined 69 consecutive cases of PRC with sufficient tissue for analysis diagnosed at the University of Virginia from 1992-2007. All cases were classified by type, including those with oncocytic features. Histologic, clinical and outcomes data were analyzed by type, with and without oncocytic features.
Results: A total of 15 (21.4%) tumors were oncocytic, the majority of which were Type 2 tumors (11 or 73.3%) (p<0.001). AMACR was positive in 93.3% and CK7 in 66.7% of OPRC. The male to female ratio of OPRC cases was nearly 1:1 in contrast to the male bias historically seen in PRC. The presence of oncocytic features was significantly associated with higher Fuhrman grade (p<0.001) and no OPRC tumors were multifocal, as opposed to 13 (23.6%) of non-OPRC tumors. At a median follow-up of 79.9 months for the entire cohort, 5-yr disease specific survival (DSS) for OPRC patients was 79.0%, which was intermediate between patients with Type 1 (93.4%) and Type 2 (44.4%) tumors. By Cox proportional hazards regression analysis, DSS of OPRC patients was significantly better than Type 2 patients (HR 0.12, 95% CI 0.03, 0.52, p=0.004), but tended to be worse than Type 1 patients (HR 2.58, 95% CI 0.78, 8.50l p=0.12).

Conclusions: We report the largest cohort of OPRC patients to date. Patients with OPRC demonstrated a survival rate intermediate between that of non-oncocytic Type 1 and non-oncocytic Type 2 PRC. Separating OPRC from Type 2 PRC improves prognostication. Although the majority of OPRC tumors were classified as Type 2 PRC, oncocytic features complicate histomorphologic typing of PRC. Therefore, separate classification of OPRC would clarify typing of PRC and improve the validity of Fuhrman nuclear grading for PRC. The study supports separation of OPRC from Type 1 and Type 2 PRC, based on both histomorphologic typing and patient survival data.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 144, Monday Morning


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