[Clinicopathological analysis of clear cell renal cell carcinoma with hemangioblastoma component]

Objective: To investigate the clinicopathological features, differential diagnosis and molecular characteristics of clear cell renal cell carcinoma (ccRCC) with hemangioblastoma component (ccRCC-HBc). Methods: Two ccRCC-HBc cases diagnosed at Fujian Provincial Hospital in September 2015 and March 2016, respectively, were included. Their morphological, immunohistochemical and molecular features were analyzed, including fluorescence in situ hybridization (FISH) detection of TFE3, TFEB and VHL genes. Related literature was reviewed to reveal the characteristics of this tumor. Results: The two cases occurred in 2 women, aged 33 and 66 years, respectively. The maximum diameters of the tumors were 4.0 cm and 8.5 cm, respectively. Histologically, the ccRCC component, representing approximate 10%-20% of the neoplasm, while the tumor cells arranged in flaky, nested, and solid distribution. The tumor cells had conspicuous nucleoli, with rich thin-wall capillary network in the stroma. The hemangioblastoma-like component, representing approximate 60%-70% of the neoplasm, showed a rich capillary network of single-layered flat endothelial cells enclosing stromal cells. The latter cell type showed a pale or eosinophilic cytoplasm exhibiting occasional lipid droplets. Rare cell nuclei appeared enlarged, pleomorphic, or bizarre. The two components were intermingled with each other. Immunohistochemically, the tumor cells were positive for PAX8, CKpan, EMA, vimentin, CD10, RCC, CAⅨ, and P504s in ccRCC area; in another area, the tumor cells were positive for α-inhibin, CD34 and vimentin, while CD10 were weakly positive. Neither TFE3 or TFEB gene split signal was detected in the 2 cases (0/2), nor was VHL gene mutation in case 2 (0/1). Conclusion: ccRCC-HBc is an extremely rare entity of ccRCC. The diagnosis is mainly based on clinical and pathological characteristics, as well as immunohistochemistry. Molecular pathology is helpful for its differential diagnosis. The primary approach of treating ccRCC-HBc is complete surgical excision and chemotherapy. The targeted treatment is helpful if possible.