This descriptive study, although small, demonstrates the difficulty in applying the current World Health Organization provisional criteria at a single institution with suggestion of an immunohistochemcial panel that may assist in the diagnosis of TCEB1-mutated RCC with leiomyomatous stroma.
Importantly, recent molecular analyses suggest the existence of another 'VHL wild-type' evolutionary subtype of clear cell RCC in addition to TCEB1 mutated RCC and clear cell papillary renal cancer.
The last 30 years of research in renal cell carcinoma (RCC) has revealed that the vast majority of RCC histologies share a recurrent pattern of mutations to metabolic genes, including VHL, MTOR, ELOC, TSC1/2, FH, SDH, and mitochondrial DNA.
Therefore, we focused on four VHL missense mutations, which affect the overlapping pVHL binding sites of p53 and Elongin C, by investigating their impact on HIFα degradation, p53 expression and signaling, as well as on cellular behavior using ccRCC cell lines and tissues.
The currently recognized 2016 World Health Organization classification for RCC subtypes is briefly discussed, including new diagnostic entities (clear cell papillary RCC, hereditary leiomyomatosis and RCC-associated RCC, succinate dehydrogenase-deficient RCC, tubulocystic RCC, and acquired cystic disease-associated RCC) and areas of evolving RCC classification, such as transcription elongation factor B subunit 1 (TCEB1)-mutated RCC/RCC with angioleiomyoma-like stroma/RCC with leiomyomatous stroma, RCC associated with anaplastic lymphoma receptor tyrosine kinase (ALK) gene rearrangement, thyroidlike follicular RCC, and RCC in neuroblastoma survivors.
Pathologically, all TCEB1-mutated tumors shared characteristic features including thick fibromuscular bands transecting the tumor, pure clear cell cytology frequently with cells showing voluminous cytoplasm, and clear cell renal cell carcinoma-like acinar areas associated with infolding tubular and focally papillary architecture.
Mutations in the von Hippel-Lindau (VHL) gene are pathogenic in VHL disease, congenital polycythaemia and clear cell renal carcinoma (ccRCC). pVHL forms a ternary complex with elongin C and elongin B, critical for pVHL stability and function, which interacts with Cullin-2 and RING-box protein 1 to target hypoxia-inducible factor for polyubiquitination and proteasomal degradation.
Defective VHL-mediated proteolysis was a common feature of ccRCC, which was caused not only by VHL inactivation but also by new hotspot TCEB1 mutations, which abolished Elongin C-VHL binding, leading to HIF accumulation.