Pathological examination: the surgical section was yellowish or brownish yellow, with uniform texture, resembling fish flesh, with complete envelope and clear boundary with surrounding tissues. 5 cases did not invade renal pelvis and renal peritoneum, no cancer metastasis was seen in the lymph nodes of renal hilum, and no tumor thrombus was seen in renal vein. Microscopic examination: The tumor cells were large or medium-sized, with abundant cytoplasm, arranged in solid sheets, and tubular vesicle-like structures were seen. The nuclei of most of the tumors were round or ovoid, moderately or mildly eccentric, and the anisotropy was not obvious. Electron microscopy: The cytoplasm of the tumor cells contained a large number of small vacuole-like structures surrounded by a single membrane, with a vacuole diameter of 150-350 nm, and some cells contained more mitochondria. Immunophenotype and special staining: low molecular weight keratin CK8 (+), vimentin (-), Hale colloidal iron staining (-). The cytoplasm was bright blue, and the tumor cells stained with different intensity, type I cells stained strongly and type II cells stained weakly. Renal suspensory cell carcinoma is a rare and specific type of renal cell carcinoma, accounting for about 4-5% of all renal cancers in the same period. In 1997, the International Union Against Cancer (UICC) and the American Joint Committee on Cancer (AJCC) proposed a new classification of renal cell carcinoma pathology, namely clear cell carcinoma, papillary carcinoma, suspicious cell carcinoma and collecting duct carcinoma. The four basic forms of renal cell carcinoma In recent years, individual cases have been reported one after another. In China, 7 cases were first reported by Lina Liu et al. in 1999, among which 6 cases were incorrectly diagnosed at the first pathology, and in 2004, Zhiyun Jiang et al. analyzed the diagnosis and treatment of 24 cases of suspicious cell carcinoma [1], of which 10 cases were diagnosed for the first time. It is mainly because the clinical manifestations of this type of cancer are similar to common kidney cancer and the pathological diagnostic criteria are not grasped. Therefore, it is important to understand the clinical and pathological characteristics of these renal cancers to guide clinical work. Patients with renal suspicious cell carcinoma have equal male to female ratio, average age of onset 55 years, slow growth and complete pseudo-envelope, and most of them are clinically diagnosed due to local pressure symptoms caused by the enlargement of the mass. The clinical stage is more often Roberson stage I, with less recurrence and metastasis. The tumor is mainly characterized by benign parenchymal occupancy on ultrasound, and the tumor is a uniform or heterogeneous medium to low echogenicity with an intact envelope; on CT scan, the tumor density is uniform, and after enhancement, the tumor border is clear. DSA shows that there are few blood vessels in the tumor. These features are helpful for clinical diagnosis. The majority of patients have no positive findings on chest X-ray and whole body bone scan. Pathological features: The tumor is spherical or nodular in shape, and the mass has an intact pseudo-envelope with a wide variation in size. The tumor is often located in the middle of the renal parenchyma, with clear boundaries and prominence toward the renal surface. The cut surface is yellowish, or uniform brownish yellow or focally grayish white, and necrotic foci are common, but bleeding is less. Its five-color appearance is less distinct than that of clear cell carcinoma. Microscopic observation: According to HE staining, it was divided into two types: (1) typical type, the cytoplasm was not stained by HE and showed more diffuse cytoplasm; (2) eosinophilic type, the cytoplasm contained acidophilic particles and was stained by eosin. Electron microscopic observation of cytoplasm filled with small vacuoles of 150-300 μm and a large number of mitochondria, thus cytoplasm lightly stained instead of containing abundant glycogen and lipid droplets, is a characteristic that differs from renal clear cell carcinoma. Renal suspicious cell carcinoma originates from the renal collecting duct epithelium, and Ortmann et al. used phycocyanin combined with way histochemical analysis to suggest that the carcinoma cells have collecting duct epithelial characteristics, i.e., they first appear as grayish-white well-bordered tumor masses in the renal medulla. Immunohistochemistry: In all tumors, tumor cells were positive for keratin epithelial cell membrane antigen and Tamn-Horsfall protein, while wave proteins were negative (Vemitin negative), and Hale colloidal iron stained cytoplasm positive. Also CK9 was highly expressed in suspicious cell carcinoma than in other renal carcinomas (reverse transcription method) [2]. In addition, immunohistochemical staining was positive for keratin CK8, CK18 and CK19. Significantly different was the tumor’s negative immunohistochemical staining for the macromolecular keratin CK1, CK5, CK10, and CK11, and negative staining for the S100 protein and the wave protein Vimentin. Gomez et al. found that 89% of renal smear cell tumors were aneuploid using DNA flow cytometry. In addition, immunohistochemical studies [3] suggest that the tumor tissue is in a low proliferative state, such as low expression of PCNA and Ki67, and negative for tumor protein P53, which indicate late metastasis and good prognosis. Genetic features: cytogenetic studies [4] have shown that the uniqueness of renal smear cell carcinoma is demonstrated by the loss of chromosomes 1, 2, 6, 10, 13, 17, 21 and multiple sex chromosomes. The deletion of short arm 3 (3P – ) in other types of renal cell carcinoma was not observed in this tumor. Because of the presence of typical cells and eosinophilic cells, renal clear cell carcinoma should be differentiated from renal clear cell carcinoma with translucent cytoplasm, and from renal eosinophilic adenoma with eosinophilic cytoplasm and other renal cell carcinomas with eosinophilic cytoplasm. 1. renal clear cell carcinoma: Although the cytoplasmic light staining and perinuclear translucency of suspicious cell carcinoma are similar to that of clear cell carcinoma, the former has clear cytosol and abundant cytoplasm; the latter has relatively small cells and some of the cytosol is clear, but the cytoplasm is hollow and even vacuolated (this is due to the blankness of the cytoplasmic glycogen lipid droplets that were dissolved during the filming process). In addition, the clear cell carcinoma showed negative Hale colloidal iron staining and positive Vimentin staining. There were a large number of glycogen lipid droplets in the cytoplasm of the clear cells without small vacuoles on electron microscopy. 2. Renal eosinophilic adenoma: It is now recognized as an independent benign tumor of the kidney. It needs to be differentiated from suspicious cell carcinoma because of its similarity in size, cell arrangement and intermediate filament expression. This tumor has a central scar with no necrosis or focal hemorrhage. The tumor cells have indistinct cytosolic membranes and the cytoplasm is filled with coarse, strongly eosinophilic granules. The nucleus is smooth and regularly rounded, located in the center of the cell, without obvious nucleolus, and nuclear fission is rare. Hale colloidal iron staining of this tumor cell was negative. The mitochondria in the cytoplasm were large and round, and were the largest among all renal tumor cells. It has been noted that cytoine 7 (SABC method) [5] can be used to differentiate between suspicious cell carcinoma, which is strongly positive, and eosinophilic tumor, which is negative. 3. Other cytoplasmic eosinophilic renal cell carcinomas: hemorrhage and necrosis are common in the naked eye and are heterogeneous in color. Most of the tumor cells are tubular or papillary in arrangement, and the cytosol is unclear. Although the eosinophilic cytoplasm is similar to that of type II cells in suspicious cell carcinoma, most suspicious cell carcinomas are composed of type 2 cells. Hale’s colloidal iron staining was negative, and CK8 and Vimentin were double expressed. Treatment and follow-up The majority of patients with renal smear cell carcinoma were treated with radical nephrectomy, and some cases were treated with partial nephrectomy or tumor removal. However, we believe that radical nephrectomy is preferable if the diagnosis is clear. Cindolo [6] analyzed the follow-up of a total of 104 patients with renal smear cell carcinoma in six European cancer centers over a mean of 38 months (1 to 153 months) and estimated a 5-year survival rate of 81%, with 5 cases (4.8%) dying from non-renal cancer and 9 cases (8.6%) from renal cancer. (8.6%) died of renal cancer. In comparing classic renal clear cell carcinoma of the same grade and stage, the prognosis of renal smear cell carcinoma is better, especially for eosinophilic renal smear cell carcinoma, and worse for renal smear cell carcinoma with spindle cell component. In Nakaigawa [7], the average follow-up of 16 patients with renal smear cell carcinoma was 40 months (6 to 160 months), and 14 patients survived, while 2 patients with stage T3 mixed with sarcomatous component and collecting duct carcinoma died of pulmonary and bone metastases (18 and 8 months after surgery). Osteogenesis of renal suspensory cell carcinoma tumors with good prognosis has also been reported.