Hemangioma-Like Clear Cell Renal Cell Carcinoma Exhibiting Aggressive Behavior and High Stage: A Case Report.

Clear cell renal cell carcinoma (CCRCC) displays a variety of architectural patterns, which are often intermingled. However, a predominant or purely multicystic growth with diffuse intracystic hemorrhage leading to hemangioma-like histomorphology, is extremely rare in CCRCC. In this article, we describe a CCRCC exhibiting a pure hemangioma-like architecture and aggressive behavior. The patient was a 73-year-old man with a tumor of the left kidney measuring 70 mm in the largest dimension. Histological examination of the nephrectomy specimen revealed a tumor composed entirely of blood filled spaces lined by a single layer of flattened or low cuboidal cells lacking high-grade features or voluminous clear cytoplasm. These cells showed diffuse immunohistochemical positivity for keratin AE1/AE3 and carbonic anhydrase 9 and focal positivity for PAX8, CD10, and alpha-methylacyl-CoA racemase. The tumor invaded the renal vein; no lymph nodes or extension of the tumor into the soft tissues of the hilum were detected (stage pT3a pNx). Using the Illumina TruSight Oncology 500 kit, a clinically significant c.3481dup, p.(Arg1161LysfsTer13) and c.2050del, p.(Gln684Asnfs4) mutations of the tet methylcytosine dioxygenase 2 () gene and c.296, p.(Pro99GlnfsTer60) mutation of the von Hippel-Lindau () gene were identified. The immunophenotype and molecular genetics of our tumor were consistent with CCRCC, suggesting that the unusual hemangioma-like growth pattern is most likely the result of extensive regressive changes. In contrast to all previously published reports, our study demonstrated that, despite the bland histological appearance, renal cell carcinomas with hemangioma-like features can invade the renal vein and follow an aggressive clinical course.