Tubulocystic renal cell carcinoma: is there a rational reason for targeted therapy using angiogenic inhibition? Analysis of seven cases

[Tubulocystic renal cell carcinoma. A rare entity in neoplastic renal pathology]

Tubulocystic renal carcinoma is an uncommon neoplasm. We present a case of a patient presenting with multiple renal colic. A nodular cystic lesion was an incidental sonographic finding which increased in size during subsequent follow-ups. The patient underwent radical nephrectomy and tubular renal carcinoma was diagnosed histopathologically and immunohistochemically.

Noncoding RNA Expression and Targeted Next-Generation Sequencing Distinguish Tubulocystic Renal Cell Carcinoma (TC-RCC) from Other Renal Neoplasms

Tubulocystic renal cell carcinoma (TC-RCC) is a rare recently described renal neoplasm characterized by gross, microscopic, and immunohistochemical differences from other renal tumor types and was recently classified as a distinct entity. However, this distinction remains controversial particularly because some genetic studies suggest a close relationship with papillary RCC (PRCC). The molecular basis of this disease remains largely unexplored. We therefore performed noncoding (nc) RNA/miRNA expression analysis and targeted next-generation sequencing mutational profiling on 13 TC-RCC cases (11 pure, two mixed TC-RCC/PRCC) and compared with other renal neoplasms. The expression profile of miRNAs and other ncRNAs in TC-RCC was distinct and validated 10 differentially expressed miRNAs by quantitative RT-PCR, including miR-155 and miR-34a, that were significantly down-regulated compared with PRCC cases (n = 22). With the use of targeted next-generation sequencing we identified mutations in 14 different genes, most frequently (>60% of TC-RCC cases) in ABL1 and PDFGRA genes. These mutations were present in <5% of clear cell RCC, PRCC, or chromophobe RCC cases (n > 600) of The Cancer Genome Atlas database. In summary, this study is by far the largest molecular study of TC-RCC cases and the first to investigate either ncRNA expression or their genomic profile. These results add molecular evidence that TC-RCC is indeed a distinct entity from PRCC and other renal neoplasms.

The evolving classification of renal cell neoplasia

The classification of renal cell neoplasia is morphologically based; however, this has evolved over the last 35 years with the incorporation of genetic characteristics into the diagnostic features of some tumors. The 2013 Vancouver classification recognized 17 morphotypes of renal parenchymal malignancy and two benign tumors. This classification included the newly established entities tubulocystic renal cell carcinoma (RCC)), acquired cystic disease-associated RCC, clear cell (tubulo) papillary RCC, microphthalmia transcription factor family translocation RCC and hereditary leiomyomatosis RCC syndrome-associated RCC. In addition to these newly described forms of RCC there are a number of novel tumors that are currently recognized as emerging entities. These are likely to be incorporated into subsequent classifications and include thyroid-like follicular RCC, succinate dehydrogenase B mutation-associated RCC, ALK translocation RCC, tuberous sclerosis complex-associated RCC, and RCC with (angio) leiomyomatous stroma.

Tubulocystic Renal Cell Carcinoma: A Rare Renal Tumor

Tubulocystic renal cell carcinoma of the kidney is a rare entity with less than one hundred cases reported so far. It was previously considered to have some similarities to various other renal cancers although this tumor has distinct macroscopic, microscopic and immuno-histochemical features. It is now a well-established entity in renal neoplastic pathology and has been recognized as a distinct entity in the 2012 Vancouver classification of renal tumors. This review aims to give an overview of tubulocystic renal cell carcinoma after extensive literature search using PubMed and CrossRef.