Sarcomatoid features and lymph node-positive disease in chromophobe renal cell carcinoma

Evaluation of American Urological Association Renal Cell Carcinoma Risk Groups for Chromophobe Renal Cell Carcinoma

OBJECTIVE

To develop and compare various models for risk stratification in chromophobe renal cell carcinoma (chrRCC). Models have been developed to predict progression-free (PFS) and cancer-specific survival (CSS) following surgery for localized renal cell carcinoma (RCC). Notably, chromophobe RCC (chrRCC) is not included in American Urological Association (AUA) risk stratification, as nuclear grading is not recommended.

METHODS

We queried our institutional registry to identify patients managed surgically for unilateral, sporadic, M0, chrRCC from 1970-2012. AUA risk groups were defined using reported criteria, excluding grade, and were compared to the Mayo system incorporating nodal involvement, perinephric/renal sinus fat invasion, and sarcomatoid differentiation. PFS and CSS were estimated using the Kaplan-Meier method. Predictive ability was summarized using c-indexes from Cox proportional hazard regression models.

RESULTS

A total of 257 patients were identified. Thirty-nine patients experienced disease progression at a median 30 months (IQR 5.0-84) and 25 died from chrRCC at a median 34 months (IQR 15-79) following surgery. PFS and CSS rates at 10 years after surgery were 84% and 90%, respectively. C-indexes for modified AUA and Mayo risk groups were similar at 0.76 and 0.75, respectively, for PFS, and 0.77 and 0.76, respectively for CSS.

CONCLUSION

The modified AUA and Mayo risk stratification systems have similarly robust c-indexes for PFS and CSS in chrRCC. These models can be used to counsel patients based on pathologic features, inform clinicians on appropriate follow-up pathways, and identify patients at risk of disease progression for enrollment in adjuvant systemic therapy trials.

The significance of sarcomatoid and rhabdoid dedifferentiation in renal cell carcinoma

Dedifferentiation in renal cell carcinoma (RCC), either sarcomatoid or rhabdoid, is an infrequent event that may occur heterogeneously in the setting of any RCC histology and is associated with poor outcomes. Sarcomatoid dedifferentiation is associated with inferior survival with angiogenesis targeted therapy and infrequent responses to cytotoxic chemotherapy. However, immune checkpoint therapy has significantly improved outcomes for patients with sarcomatoid dedifferentiation. Biologically, sarcomatoid dedifferentiation has increased programmed death-ligand 1 (PD-L1) expression and an inflamed tumor microenvironment, in addition to other distinct molecular alterations. Less is known about rhabdoid dedifferentiation from either a clinical, biological, or therapeutic perspective. In this focused review, we will discuss the prognostic implications, outcomes with systemic therapy, and underlying biology in RCC with either sarcomatoid or rhabdoid dedifferentiation present.

Clinicopathologic and Immunohistochemical Characterization of Sarcomatoid Chromophobe Renal Cell Carcinoma: An Analysis of 22 Cases

Sarcomatoid differentiation in chromophobe renal cell carcinoma (ChRCC) is a rare finding and a significant predictor of worse outcomes. When the sarcomatoid component overgrows the conventional component or is the only component on a biopsy, the differential diagnoses encompass a variety of entities. Therefore, we reviewed 22 sarcomatoid ChRCCs and characterized the immunophenotype. Given that renal carcinomas with sarcomatoid features may benefit from immune checkpoint inhibitor-based therapy we also assessed the programmed death-ligand 1 (PD-L1) (28-8) expression. DOG1, CD117, cytokeratin 7, and PAX8 were negative in 100%, 88%, 63%, and 44% of the sarcomatoid components, respectively. GATA3 was expressed in 31% of the conventional components and in 50% of the sarcomatoid components. One conventional and 3 sarcomatoid components expressed PD-L1. Sarcomatoid ChRCCs have a high propensity for metastases and cancer progression. Distant metastatic disease was seen in 73% of the cases and median survival in this cohort was <1 year. The sarcomatoid portion had increased expression of PD-L1 and frequent loss of expression of multiple immunohistochemical markers associated with ChRCC. Half of the sarcomatoid ChRCC exhibited GATA3 expression, 3 of which did not express PAX8.