[1004] Rhabdoid Differentiation in Renal Cell Carcinomas (RCCs): Clinicopathologic Analysis of 76 Cases

Christopher G Przybycin, Jesse K McKenney, Mariana Mantoan-Padilha, Jordan P Reynolds, Cristina Magi-Galluzzi. Cleveland Clinic, Cleveland, OH

Background: Rhabdoid differentiation (RD) has been associated with aggressive behavior in RCCs and is often considered of similar prognostic importance to sarcomatoid differentiation (SD), which warrants a Fuhrman grade of 4. We report a clinicopathologic analysis of a series of RCCs with RD and compare clinical outcome with a cohort of RCCs with SD.
Design: We searched for kidney specimens with the word “rhabdoid” resected at our institution between 1997 and 2011. Diagnoses were confirmed by re-review. Primary tumors and metastases were evaluated for: percentage of RD, percentage of SD (if any), percentage of necrosis, grade of the non-rhabdoid/non-sarcomatoid component, and staging parameters. To determine any isolated effect of RD, follow-up data were examined for patients with clear cell RCCs having RD but lacking SD, and were compared with those from a cohort of patients with clear cell RCCs having SD but lacking RD.
Results: 76 primary RCCs with RD were found: 68 clear cell RCCs, 1 papillary RCC, 1 chromophobe RCC, and 6 RCCs, unclassified. Sixty-two cases (82%) were stage pT3a or higher, and nodal metastases were seen in 17 (22%) cases. RD comprised over half of tumor volume in 31 (41%) cases. Twenty-four (32%) cases also had SD, which was contiguous with the RD in 22 (92%) cases; the percentage of SD was >50% in 33% of cases. Necrosis was present in 66 (87%) cases, and was extensive (>50%) in 14 (18%) cases. Distant metastases were present in 27 (36%) cases, 21 of which had available slides. Of these, 14 (67%) showed RD in the metastasis. Follow-up data were available for 39 of the clear cell RCCs containing RD without SD (mean = 22 mo). Of these, 12 died of disease and 4 of unknown causes; 23 had distant metastasis. When compared with a separate cohort of 125 patients with clear cell RCCs containing SD without RD using an extensive univariable analysis (including stage) with subsequent multivariable adjustment, only tumor type (rhabdoid vs. sarcomatoid), patient age, and follow-up months were significant at p<0.05. Adjusting for these statistically significant variables, tumors with RD were less likely to develop distant metastases than their sarcomatoid counterparts: 59% versus 78% (OR 0.38 CI: 0.17-0.87, P=0.0224).
Conclusions: RD in RCC was associated with high tumor stage, frequent metastasis, and frequent contiguous SD, but was associated with fewer distant metastases compared to RCC with SD.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 137, Wednesday Morning

 

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