Renal cell carcinoma unclassified with medullary phenotype (RCCU‐MP) is a rare variant of renal medullary carcinoma (RMC) characterized by loss of SMARCB1 (INI1 / SNF5 / BAF47) protein expression in patients without sickle cell trait. Here, we report a case of RCCU‐MP in a Japanese patient who had experienced colon cancer 13 years ago, gastric cancer 11 years ago and lung cancer 9 years ago and had received hemodialysis for 15 years. This is the first report of RCCU‐MP in Japan. The patient was not of African descent, and did not have SCT or any other hereditary blood abnormality typical of RMC. The tumor was located in the left kidney, and was composed histologically of rhabdoid cells with marked lymphocyte infiltration; it was immunohistochemically negative for SMARCB1. We were, however, unable to detect mutation in the SMARCB1 gene, reduced messengerRNA expression, or deletion or translocation of chromosome 22, where the SMARCB1 gene is located. These results suggest that RCCU‐MP may not involve the hemizygous loss of this gene noted in typical RMC cases.

A meningocele is a congenital neural tube defect, and the majority of the meningocele cases are identified perinatally. We present the case of a 67-year-old patient with a sacral meningocele undiagnosed until the removal of a symptomatic epidermal inclusion cyst adjacent to it. Cerebrospinal fluid leakage occurred due to an incision in an undiagnosed meningocele adjacent to the epidermal inclusion cyst. Repair of the cerebrospinal fluid leakage was performed successfully without any deficit. The present case underscores the importance of considering a meningocele as a differential diagnosis for a mass occurring in the midline of the back at any age.

A 10-year-old male child patient was admitted with a chief complaint of progression of lower limb weakness lasting for 5 weeks. An initial clinical picture was reminiscent of Guillain–Barré syndrome. Repeated cerebrospinal fluid (CSF) cytological examinations were negative for neoplastic cells, but leptomeningeal biopsy targeting positron emission tomography (PET) avid lesion confirmed the invasion of tumor cells which were negatively stained with Brahma-related gene 1. An extensive literature review identified five cases of primary diffuse leptomeningeal atypical teratoid/rhabdoid tumors, and the clinical characteristics, including ours, were characterized as follows: (1) there was a bimodal age distribution in young children and adolescents with a male predominance, (2) roughly half of the patients fulfilled the diagnostic criteria of albuminocytologic dissociation and CSF cytology was neither sensitive nor specific to establish a definitive diagnosis, and (3) cerebrospinal magnetic resonance imaging findings were mostly indistinguishable from those of infectious or inflammatory diseases. We would like to suggest that primary leptomeningeal tumor should be included in the differential diagnosis of progressive polyneuropathy even in the absence of CSF cytological findings and implementation of preoperative PET may enhance the diagnostic accuracy of such a miscellaneous central nervous system tumor.