Clear cell renal cell carcinoma (ccRCC) with predominant papillary features is best classified as a rare morphologic variant of ccRCC, not MiT family translocation or papillary RCC, according to an analysis of 23 tumors.
Areas of papillary pattern made up anywhere from 40% to 100% of the 23 tumors. Even so, cytology and immunohistochemical and genetic testing was most consistent with ccRCC, and tumors were negative for TFE3 protein, which ruled out MiT family translocation RCC, reported Reza Alaghehbandan, MD, and his associates. The report is in Annals of Diagnostic Pathology.
The findings help clarify where ccRCC fits in the diagnostic tree when there’s significant papillary morphology, something that hasn’t been clear until now. The proper classification matters because it carries treatment implications; for instance, ccRCC generally responds well to immunotherapy and targeted therapy, but papillary RCC does not, so doctors often recommend treatment through a clinical trial.
“The presence of mixed morphologic components in renal neoplasms in general and in ccRCCs in particular can be puzzling in routine practice, which can potentially lead to misdiagnosis.” Getting it right is “crucial” to ensure the best treatment, said Dr. Alaghehbandan, of the University of British Columbia, Vancouver, and his associates.
Cytokeratin 7 (CK7) staining was negative in the nonpapillary areas of 20 tumors (87%), and only focally positive in three (13%). In contrast, clear cell papillary RCC is strongly and diffusely positive for CK7.
In papillary areas, Alpha-methyl CoA racemase was positive or focally positive in 17 tumors (73.9%); in nonpapillary areas, it was positive or focally positive in 22 (95.6%). Carbonic anhydrase IX was mainly negative in both nonpapillary and papillary areas, while vimentin and CD10 were positive or focally positive in both.
Patients were a mean of 65.2 years old, and 19 were men. The median tumor size was 6.5 cm. At a median follow-up of 2.5 years, two patients had died of their disease, and two had developed metastasis.
There was no industry funding, and the investigators didn’t have any disclosures.
SOURCE: Alaghehbandan R et al. Ann Diagn Pathol. 2018 Nov 22. doi: 10.1016/j.anndiagpath.2018.11.004.