TCEB1-mutated Renal Cell Carcinoma: A Distinct Genomic and Morphologic Subtype

Integrated sequencing analysis identified a group of tumors among clear cell renal cell carcinomas characterized by hotspot mutations in TCEB1 (a gene that contributes to the VHL complex to ubiquitinate hypoxia inducible factor). We analyzed 11 tumors from two distinct cohorts with TCEB1 mutations along with an expanded cohort to assess whether these should be considered an entity distinct from clear cell renal cell carcinoma and clear cell papillary renal cell carcinoma. All tumors were characterized by hotspot mutations in TCEB1 Y79C/S/F/N or A100P. Morphologic and immunohistochemical characteristics of the tumors were assessed by two experienced genitourinary pathologists. Clinical and pathologic variables, copy number alterations, mutations and expression signatures were compared to a cohort of TCEB1 wild type tumors. All TCEB1 mutated tumors were VHL and PBRM1 wild type and contained distinct copy number profiles including loss of heterozygosity of chromosome 8, the location of TCEB1 (8q21.11). All tumors lacked the clear cell renal cell carcinoma signature 3p loss and contained distinct gene expression signatures. None of the clear cell papillary tumor harbored TCEB1 mutations. Pathologically, TCEB1-mutated tumors all shared characteristic features including thick fibromuscular bands transecting the tumor, pure clear cell cytology frequently with cells showing voluminous cytoplasm, clear cell renal cell carcinoma-like acinar areas associated with in-folding tubular and focally papillary architecture. The presence of voluminous cytoplasm, absence of luminal polarization of tumor nuclei and lack of extensive cup-like distribution of carbonic anhydrase IX expression distinguish it from clear cell papillary carcinoma. No patients had developed metastases at last follow-up (median 48 months). In sum, TCEB1-mutated renal cell carcinoma is a distinct entity with recurrent hotspot mutations, specific copy number alterations, pathway activation and characteristic morphologic features. Further clinical followup is needed to determine whether these tumors are more indolent compared to conventional clear cell renal cell carcinoma.