One case of sarcomatoid renal cell carcinoma (SRCC) is a special type of renal cancer, which is now widely considered as a histopathological change in the transformation of renal cell carcinoma to a highly malignant stage. The histological structure resembles soft tissue sarcoma, which is easily misdiagnosed as renal sarcoma or carcinosarcoma, and is rarely seen clinically. 1. Clinical data The patient, male, 61 years old, came to the clinic with “hematuria twice and a cystic mass in the left kidney with pain in the left side of the back for more than one month”. He reported a slightly high afternoon temperature and weight loss of 5 kg since two weeks before admission, and his temperature fluctuated from 37.0 to 37.5°C at 3 pm after admission. Previous history of hypertension for 8 years, oral nifedipine extended-release tablets 20mg/day, controllable; no history of other chronic diseases; no history of hepatitis, tuberculosis. Physical examination: superficial lymph nodes were not enlarged, and a mass could be found in the left kidney area, with positive pressure pain and percussion pain, and local skin tension. Ultrasound showed that the left kidney was a hypoechoic solid occupancy with a size of 5.6cm×4.7cm×4.5cm, the border was still clear, the renal sinus was in the center, and no separation was seen. CT scan showed a cystic solid lesion in the middle pole of the left kidney, measuring about 7.5cm×7.0cm×6.5cm, and multiple lymph nodes were seen in the perirenal abdominal aorta. Laboratory examination: blood cell analysis suggested that red blood cell count was 3.76×1012/L and hemoglobin was 110 g/L. Urine routine red blood cells (++++) and white blood cells (+), liver and kidney function were normal. Blood glucose: 6.49 mmol/L. Blood calcium normal, blood phosphorus 0.91 mmol/L. Serum iron: 6.0 umol/L. Hematocrit: 56 mm/end of 1st h. Preoperative diagnosis: cystic renal carcinoma of the left kidney. Radical left nephrectomy was performed under inhalation general anesthesia through an 11-rib incision. Intraoperatively, he saw that the tumor was located in the upper pole of the left kidney with adhesions to the surrounding tissues, the hilum and the parietal aortic lymph nodes were enlarged and fused, and the normal structures of the adrenal area were lost, and only the hard adherent mass with obvious adhesion to the tail of the pancreas was seen. The mass was located in one pole of the kidney, measuring about 8 cm x 7 cm x 6 cm, with a fish, jelly-like, grayish gray-red color, poorly delineated from the surrounding tissues, with hemorrhagic necrosis in some areas, and poorly delineated from the surrounding renal tissues, invading the peritoneum and renal sinus. Pathological examination: sarcomatoid renal cell carcinoma with extensive necrosis, metastatic cancer nodules were seen in the fatty tissue around the pancreas and kidney, and part of the pancreatic lobules in the adhesion between the tumor and the tail of the pancreas were degenerative and necrotic, without cancer. The postoperative whole-body bone scan suggested suspicious metastases in the thoracic spine. The patient had good postoperative wound healing and local pain relief, and targeted therapy was started 9 d later. At present, follow-up observation is in progress. 2. Discussion The concept of sarcomatoid renal cell carcinoma (SRCC) was first proposed by FARROW et al. in 1968, which is a specific type of renal cancer. Early on, SRCC was thought to be a histologic subtype of renal cell carcinoma, but now it is believed that sarcomatoid renal cell carcinoma is only a poorly differentiated type derived from other histologic subtypes rather than an independent tumor type.SRCC accounts for about 1%-5% of renal cell carcinoma and has a more aggressive biological behavior, such as local infiltration, recurrence and distant metastasis, and is a highly aggressive, highly malignant, and easily It is a highly aggressive, highly malignant, metastatic and early recurring tumor type. The exact etiology of the tumor is still unknown. It is believed that the tumor is the result of bidirectional differentiation of stem cells with multidirectional differentiation potential into epithelial and mesenchymal tissues under the action of pro-carcinogenic factors. Clinical diagnosis is difficult, and its clinical symptoms are mainly local pain, mass, hematuria, cough or coughing up blood, wasting and weakness, fever, etc., which lack specificity. At present, there are still differences in the diagnosis and treatment of SRCC at home and abroad, but radical nephrectomy is still the main treatment for SRCC, and chemotherapy and radiotherapy are not effective, while targeted therapy is satisfactory. In conclusion, patients with SRCC have poor prognosis and shorter survival than other renal cell carcinoma patients. Even with combined treatment, most patients die within 1 year because of extensive tumor metastasis. Clinical stage, tumor size, degree of tumor necrosis, presence of lymph nodes and distant metastases are important factors affecting patients’ prognosis.