Mucinous tubular and spindle cell carcinoma (MTSCC) is rare in renal cell carcinoma (RCC) and usually demonstrates a low nuclear grade and a better prognosis compared with other RCCs. The authors present a case report of MTSCC containing an area of Fuhrman nuclear grade 3, in addition to an area with a micropapillary pattern. An 82-year-old man consulted a hospital due to macrohematuria, and a tumor in the right kidney was detected. The tumor was resected and histologically examined. The tumor consisted of various growth patterns: Elongated tubular structure, a papillary structure containing a micropapillary pattern and solid pattern with spindle cells. The tumor cells demonstrated Fuhrman nuclear grades 2 and 3. Invasion into the lymph vessel and metastasis into the regional lymph node were observed. Thus, the tumor was diagnosed as a high grade MTSCC. Five months following resection, a computed tomography scan suggested metastasis of the tumor into the para-aortic lymph nodes and liver, and the patient succumbed to brain metastasis. When MTSCC of kidney is observed, careful histological observation is important to avoid missing a high nuclear grade area.

Malignant rhabdoid tumours (MRTs) in the kidney are rare paediatric tumours that are extremely rare in adults. We herein report the case of an adult patient with a renal MRT. A 79-year-old Japanese woman was found to have a tumour sized 63x48 mm in the left kidney, in addition to multiple metastatic bone and lymph node lesions. The needle biopsy specimen obtained from the patient's kidney revealed tumour cells with rhabdoid characteristics: The cells appeared large, round or polygonal, with eccentrically located nuclei and prominent nucleoli. Immunohistochemically, the tumour cells were positive for vimentin, epithelial membrane antigen, CAM 5.2, and p53, and negative for INI1, cytokeratin (CK)7, CK20, α-methylacyl-CoA racemase, S100, CD45, renal cell carcinoma marker, anaplastic lymphoma kinase, α-smooth muscle actin, desmin, MyoD, myogenin, human melanoma black 45 and melan A. Therefore, the tumour was diagnosed as an MRT located in the kidney. Although the patient was treated with axitinib, a tyrosine kinase inhibitor, the renal tumour and its metastatic lesions continued to progress, and the number of metastatic lesions increased. The patient succumbed to the disease 5 months after the first hospital visit. The disease progression was rapid, with a poor prognosis, consistently with previous reports that of MRTs in the adult kidney.