[822] Unclassified Renal Cell Carcinoma: A Contemporary Study of 116 Cases with Emphasis on Tumors with Aggressive Behavior

Ying-Bei Chen, Hikmat Al-Ahmadie, Anuradha Gopalan, Samson W Fine, Victor E Reuter, Satish K Tickoo. Memorial Sloan-Kettering Cancer Center, New York

Background: Renal cell carcinoma, unclassified (URCC) is a diagnosis given to renal cell tumors that do not fit into one of established histologic subtypes in the current WHO classification. They constitute 3-5 % cases in several surgical series. The clinicopathologic spectrum and genetic alterations in URCC have not been well studied.
Design: Using current diagnostic criteria for URCC, we retrospectively identified a cohort of 116 patients who were diagnosed and surgically treated at our institution in 1989-2010. Low grade oncocytic tumors were excluded for the purpose of this study.
Results: 68 (59%) patients were men and 48 (41%) women. Mean age at nephrectomy was 58.1 years (11-86), mean tumor size was 6.7 cm (1.3-18.0), and 15 patients had multiple tumors bilaterally or ipsilaterally. Median follow-up is 26 months (6-202). Based on histologic features, we were able to divide the tumors into 3 main groups: I). Tumors with a mixture of clear and eosinophilic cells, variable architectural patterns including alveolar, papillary and solid, and without extensively infiltrative borders; many of these resembled translocation-associated RCC, but were TFE3/B negative.(n=31;27%) II). Tumors lacking clear cells, with variable but often prominent papillary architecture and extensively infiltrative borders; some of these raised the possibility of collecting duct carcinoma or type 2 papillary RCC.(n=57;49%) III). Tumors predominantly composed of high-grade oncocytic cells in variable architectural patterns other than papillary.(n=28;24%) There was no significant difference in age, gender or tumor size among the 3 groups. As summarized in table, there were significant differences among the groups for high tumor stage, lymph node and distant metastases at presentation, as well as death due to disease, with tumors in group II appearing to be the most aggressive.

Histologic GroupsN≥ pT3 (%)*N1/2 (%)*M1 (%)*Met. for M0 Pt in F/U (%)DOD (%)
I3119 (61)7 (23)2 (6)9 (29)7 (23)
II5738 (67)29 (51)13 (23)17 (30)27 (47)
III286 (21)003 (11)2 (7)
p value<.001<.001<.001.133<.001
* Stage at nephrectomy

Conclusions: Sub-grouping high-grade URCC by morphology reveals groups with dissimilar clinical course and outcome. Tumors in group II (with usually prominent papillary architecture, infiltrative borders, and lacking clear cells) present with early metastasis and are associated with highest cancer-specific mortality. Further studies including mutation and expression analysis are ongoing to identify molecular alterations which may help better define subsets of tumors in the URCC category.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 103, Wednesday Morning


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