von Hippel-Lindau (VHL) disease is characterized by neoplastic and cystic lesions, such as central nervous system (CNS) hemangioblastoma and clear cell renal cell carcinoma (RCC), arising in multiple organs. Here, we report a case of an RCC that metastasized to a spinal hemangioblastoma in a patient diagnosed with VHL disease. This is a unique case study because visceral neoplasms rarely metastasize to the CNS. The patient had undergone posterior fossa surgery for the removal of hemangioblastomas in the right cerebellar hemisphere as a child. He was diagnosed with RCC at the age of 20 years, and he underwent partial nephrectomy at the age of 35 years. The patient underwent surgical removal of a spinal tumor from Th8, which was also diagnosed as a hemangioblastoma at the age of 40. However, the residual spinal tumor rapidly regrew within 1.5 years. A second surgery was performed due to progressive leg motor weakness. The resected tumor from the second surgery had two distinct components between the tumor center and the margin. Immunohistochemistry of CD10, PAX 8, and inhibin A demonstrated the predominant region of the tumor was RCC. Pathological findings confirmed tumor-to-tumor metastasis of the RCC migrating into residual spinal hemangioblastoma. It can be challenging to distinguish hemangioblastoma from RCC in neuroimaging. We suggest that tumor-to-tumor metastasis should be considered as a differential diagnosis if benign tumors grow rapidly, even if the pathological diagnosis does not initially confirm malignancy. The biological mechanisms of RCC migrating into residual hemangioblastoma are discussed.

Background: Subdural hematoma (SDH) at a remote operative site is uncommon following neurosurgical procedures. However, supratentorial SDH is one of the rare complications following microvascular decompression (MVD). We report a case of supratentorial SDH following MVD. The welling of cerebrospinal fluid (CSF) in the cerebellomedullary fissure was observed unexpectedly during the dissection. It is a signal case that can improve our understanding of the occurrence of such rare complications and of possible mechanisms. Case presentation: A 54-year-old woman was diagnosed with left hemifacial spasm (HFS) and had been receiving botulinum toxin injections since 10 years before surgery. CSF welling-up in the cerebellopontine cistern was noticed by the surgeon during the arachnoid dissection. MVD was performed completely. A thin supratentorial SDH was found on the right side (contralateral) on immediate postoperative computed tomography (CT). The SDH was asymptomatic, and the size of hematoma did not increase in follow-up CT scans after surgery. During the follow-up period, she was relieved of HFS. CSF welling-up can be considered the time of initiation of the hemorrhage. Conclusion: Limited case reports of supratentorial SDH following MVD have been published, and none of them have reported time of initiation of the hemorrhage. The phenomenon of abnormal CSF welling-up in the cistern could be a sign of remote supratentorial hemorrhage.

Recent DNA methylation profiling clarified several rare entities of pediatric CNS tumors from institutionally-diagnosed primitive neuroectodermal tumors (PNETs). One of which is CNS high-grade neuroepithelial tumor with BCOR alteration (CNS HGNET-BCOR), and it carries in-frame internal tandem duplications (ITD) of the BCL6 corepressor (BCOR) in exon 15. In the report, we describe a case of immunohistologically-diagnosed CNS HGNET-BCOR, which lacks exon 15 ITD of BCOR. A five-year-old boy visited a local hospital complaining uncontrolled vomiting for two months, and magnetic resonance imaging (MRI) showed a large well-circumscribed mass in his left cerebellum with ventricular dilatation. He referred to our hospital, and an additional MRI revealed diffuse and weak enhancement of gadolinium and low ADC values in mass. Immediately, he underwent total removal of the tumor and ventricular drainage, and his consciousness recovered soon after surgery. The tumor presented high BCOR expression by IHC, but target PCR did not identify exon 15 ITD of BCOR. As the previously-reported clinical and imaging features of CNS HGNET-BCOR resembled our case, we clinically diagnosed it as a similar phenotype of CNS HGNET-BCOR without exon 15 ITD. He received 60 Gy of extended-local irradiation with concomitant temozolomide and discharged without any neurological deficits. Since BCOR alterations, including ITD, gene fusions, and mutations, play an oncogenic role in several cancers, the present case might harbor another gene aberration of BCOR.