SclerosingTSC1mutated renal cell carcinoma: An unusual pattern mimickingMITFfamily translocation renal cell carcinoma

Abstract

The tuberous sclerosis genes andMTORare increasingly being found to have important roles in novel subtypes of renal cancer, particularly emerging entities eosinophilic solid and cystic renal cell carcinoma (RCC) and high-grade oncocytic renal tumor (HOT)/RCC with eosinophilic and vacuolated cytoplasm. We report a unique renal neoplasm in a 66-year-old woman that initially mimicked MITF family translocation RCC due to mixed clear and eosinophilic cells, extensive stromal hyalinization, and psammoma bodies, yet which was negative forTFE3andTFEBfluorescence in situ hybridization and a next generation sequencing (NGS) gene fusion assay. Cytoplasmic stippling triggered consideration of TSC-associated neoplasms, and a targeted NGS assay revealed a variant in exon 21 ofTSC1resulting in c.2626G>T p.(Glu876*) truncating mutation. This report adds to the morphologic spectrum of TSC-related renal neoplasms, including prominent stromal hyalinization as a potentially deceptive pattern. Due to the overlap in cytoplasmic stippling between eosinophilic solid and cystic RCC and HOT/RCC with eosinophilic and vacuolated cytoplasm, it is debatable which category this example would best fit. Further understanding of these entities and other renal neoplasms with alterations in the TSC genes will elucidate whether they should be considered a family of tumors.