Sarcomatoid Chromophobe Renal Cell Carcinoma with Heterologous Elements: A Rare Form of an Aggressive Tumor

Abstract

Abstract Introduction/Objective Chromophore renal cell carcinoma (ChRCC) accounts for approximately 4-10% of renal cell carcinomas. Compared with other subtypes of renal cell carcinoma, ChRCC generally has a more favorable outcome; however, sarcomatoid transformation is greatest in ChRCC. We report a case of ChRCC with extensive sarcomatoid transformation, which included the heterologous elements of osteosarcoma and chondrosarcoma. The presence of heterologous elements is distinctively rare, with only twelve previous cases in the English literature. Methods/Case Report A 64-year-old man presented with left flank pain and night sweats. The abdominal MRI showed a large exophytic hypervascular mass in the left kidney with metastasis to the left para-aortic lymph nodes. The patient underwent radical nephrectomy. Two months after the surgery, the patient was found to have extensive bony metastases. On gross examination, the nephrectomy specimen showed an 18 cm tumor replacing almost the entire kidney. The cut surface was white to tan with areas of hemorrhage and necrosis. Microscopic examination revealed a predominantly sarcomatoid ChRCC (nearly 80% of the tumor) with heterologous chondrosarcoma and osteosarcoma. The tumor extended into the perinephric adipose tissue and the adrenal gland. Multiple para-aortic lymph nodes contained sarcomatoid tumor with heterologous elements. Results (if a Case Study enter NA) NA. Conclusion ChRCC is frequently considered a more indolent renal cell carcinoma. It is important to recognize its higher propensity for sarcomatoid transformation. The presence of heterologous elements is exceptionally uncommon. Whether this correlates with a more aggressive tumor is not known because of the paucity of such cases.