Two Cases of Renal Cell Carcinoma Harboring a Novel STRN-ALK Fusion Gene

Abstract

Anaplastic lymphoma kinase (ALK) translocation renal cell carcinomas (RCCs) have been reported by several independent groups in recent times. The clinical behavior and histopathologic characteristics of these carcinomas are not fully understood because of the paucity of cases reported. Here, we describe 2 cases of RCC harboring a novel striatin (STRN)-ALK fusion. The first case was a 33-year-old woman with no sickle cell trait who underwent nephrectomy for right renal mass and had late recurrence in para-aortic lymph nodes twice 10 and 12 years after initial surgery. After the second recurrence, she was carefully observed without any treatment. Twenty-six years after the initial nephrectomy, the second para-aortic lymphadenectomy was performed, and gastrectomy was performed for newly developed primary gastric cancer. The resected para-aortic lymph nodes were largely replaced by metastatic carcinoma. The second case was a 38-year-old man with no sickle cell trait who underwent cytoreductive nephrectomy followed by sunitinib therapy for metastatic RCC. In both cases, the tumor showed solid, papillary, tubular, and mucinous cribriform structures. Psammoma bodies were occasionally seen in the stroma. Tumor cells had a large nucleus and prominent nucleoli with predominantly eosinophilic cytoplasm. Rhabdoid cells and signet-ring cells were also observed. Intracytoplasmic mucin deposition and background mucinous stroma were confirmed. In the second case, tumor necrosis was seen in some areas. Tumor cells exhibited diffuse positive staining for ALK in both cases. ALK translocation was confirmed by fluorescent in situ hybridization, and further gene analysis revealed a STRN-ALK fusion. These cases provide great insights into ALK translocation RCCs.