Correlation of Recently Proposed Chromophobe Tumor Grade (CTG) with Initial Stage in 82 Chromophobe Renal Cell Carcinomas (RCC) from a Single Institution.
Elizabeth Weinzierl, Benjamin Chung, Jesse McKenney. Stanford, Stanford, CA
Background: It is well-recognized that the Fuhrman grading system is not appropriate for chromophobe RCC, because the majority of cases would receive a Fuhrman grade > 3 despite the expected indolent behavior. A novel grading system specific to chromophobe RCC was recently proposed (Paner et al. Am J Surg Pathol 2010;34(9):1233-40), but has not yet been evaluated by other investigators.
Design: All available chromophobe RCCs were identified from the surgical pathology archives of a single hospital from 1987-2010. No consultation cases were included. Patient age and sex were recorded. Each case was re-reviewed by two pathologists to confirm diagnoses and each case was graded following the novel chromophobe tumor grade system criteria described by Paner et al. The percentage of tumor comprised of each grade was also recorded. Grade was correlated with AJCC 7th ed. stage at initial surgery.
Results: 82 chromophobe RCCs were identified. 53 patients were male and 29 female. The patients' ages ranged from 17 to 87 years (mean=60; median=61). 53 (65%) were CTG1, 27 (33%) CTG2, and 2 (2%) CTG3. Both CTG3 cases had sarcomatoid differentiation. All cases with CTG2 also had foci of CTG1; the percentage of tumor comprised of CTG2 ranged from less than 5% to 60%. Cases presenting at AJCC 7th ed. stage > 3 were as follows: 9/53 CTG1 (17%), 4/27 CTG2 (15%), and 2/2 CTG3 (100%). The anatomic stage matched the pT stage for all cases. Only one case (1.2%), which was CTG2 in 15% of the tumor, presented with lymph node metastasis. The one case presenting with pT4 disease had sarcomatoid differentiation (i.e. CTG3). No distant metastases were present at the time of initial diagnosis in any of the cases.
Conclusions: The newly proposed chromophobe tumor grade did not correlate with AJCC stage in this study; however, the number of cases with CTG3 and/or extrarenal extension or metastatic disease was extremely limited. In contrast to the Fuhrman grading system, the chromophobe tumor grade system assigned a low grade designation (CTG1) to the majority of cases in this series. Further study of the chromophobe tumor grade system is warranted, and correlation with long-term clinical follow-up data is ongoing to determine the utility of this novel chromophobe grading system for the prediction of subsequent recurrence and/or metastasis.
Category: Genitourinary (including renal tumors)
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 91, Wednesday Morning