[961] Sporadic Hybrid Oncocytic/Chromophobe Tumor (HOCT) of the Kidney – The Quest To Define It Continues!.

Kiril Trpkov, Matteo Brunelli, Guido Martignoni, Asli Yilmaz. University of Calgary, AB, Canada; Universitá di Verona, Verona, Italy

Background: HOCT of the kidney have been typically described in patients with Birt-Hogg-Dubé syndrome and in renal oncocytosis. Although rare sporadic HOCT have also been described, it remains uncertain what is the spectrum of their features, their long-term behavior and if they are different or similar to the hybrid tumors in Birt-Hogg-Dubé and oncocytosis. To our knowledge, only one multiinstitutional study has attempted to better characterize sporadic HOCT (Virchows Arch 2010; 456:355-65).
Design: We studied 6 tumors from patients who had no clinical evidence of BHD or renal oncocytosis. The tumors showed oncocytoma-like appearances with focal chromophobe-like changes: perinuclear halos, nuclear irregularities (raisinoid nuclei) and/or prominent cell membranes. All tumors were diffusely positive for C-kit and, similar to oncocytoma, only rare cells were positive for CK7 (less than 5% of cells), which is different from the diffuse CK7 positivity in chromophobe renal cell carcinoma (RCC). We performed fluorescence in-situ hybridization (FISH) to evaluate the numerical chromosomal alterations in 5 of 6 cases.
Results: HOCT were identified in 3 males and 2 females (one male patient had bilateral solitary tumors). Mean patient age was 72 years (range, 57 to 83). All tumors were stage pT1 (4 were pT1a and 2 were pT1b). The tumors ranged from 3.2 to 6.5 cm (mean 4.5). On gross examination, 5 tumors were light-brown and 1 tumor was mahogany-brown. No central scar was seen grossly in any tumor. On light microscopy, 5 tumors showed combinations of solid and tubulo-alveolar growth patterns and 1 tumor was tubulocystic. All cases showed only luminal staining for colloidal iron (Müller-Mowry) of variable intensity, similar to oncocytoma. Parvalbumin was positive in 3/3 evaluated cases. In 3/5 tumors evaluated by FISH, there were multiple chromosomal monosomies (loss: 1, 6, 10; 2, 6, 10 and 1, 2, 6, 10), as typically seen in chromophobe RCC. In the remaining 2/5 cases evaluated by FISH, in addition to chromosomal losses (loss 1, 2 and 2, 6, 10, respectively), we also found chromosomal gains (gain: 6, 10, 17 and 1, 17, respectively). After a mean follow-up of 68 months (range, 36 to 109), no recurrence or metastatic disease were documented in any patient.
Conclusions: Sporadic HOCT of the kidney are indolent tumors which show features intermediate between oncocytoma and chromophobe RCC. Although some sporadic HOCT exhibit multiple chromosomal losses, similar to chromophobe RCC, some HOCT show chromosomal gains, similar to those seen in oncocytosis, but not in chromophobe RCC.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 89, Wednesday Morning


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