Masked malignant phenotype with a benign appearance: beat-up copy number profile may be the key for hemangioblastoma dissemination

Embryonal tumor with multilayered rosettes arising from the internal auditory canal of an adult: Illustrative case with molecular investigations

Embryonal tumors with multilayered rosettes (ETMRs) are aggressive central nervous system (CNS) tumors that usually occur in young children. Here, we describe the first incidence of ETMR in an adult patient that also originated in the novel location of the internal auditory canal (IAC). The 36-year-old patient initially presented with unsteadiness, diplopia, and tinnitus. The tumor in the IAC was discovered on brain magnetic resonance imaging, and gross total resection was performed followed by pathological and molecular diagnosis. The patient received whole brain and spinal cord radiotherapy after an intracranial recurrence and adjuvant chemotherapy consisting of four cycles of ifosfamide, cisplatin, and etoposide. Progression was rapid; however, the patient survived for 22 months after diagnosis before succumbing to the disease. Molecular investigation revealed a DICER1 mutation at exon 25, and methylation classification categorized the tumor as ETMR, non-C19MC-altered. This case underscores the diverse possible presentations of ETMR, DICER1-mutated and the importance of molecular techniques to characterize and promptly treat atypical ETMR.

Intraventricular central neurocytoma molecularly defined as extraventricular neurocytoma: a case representing the discrepancy between clinicopathological and molecular classifications

Central neurocytoma (CN) is classically defined by its intraventricular location, neuronal/neurocytic differentiation, and histological resemblance to oligodendroglioma. Extraventricular neurocytoma (EVN) shares similar histological features with CN, while it distributes any site without contact with the ventricular system. CN and EVN have distinct methylation landscapes, and EVN has a signature fusion gene, FGFR1-TACC1. These characteristics distinguish between CN and EVN. A 30-year-old female underwent craniotomy and resection of a left intraventricular tumor at our institution. The histopathology demonstrated the classical findings of CN. Adjuvant irradiation with 60 Gy followed. No recurrence has been recorded for 25 years postoperatively. RNA sequencing revealed FGFR1-TACC1 fusion and methylation profile was discrepant with CN but compatible with EVN. We experienced a case of anatomically and histologically proven CN in the lateral ventricle. However, the FGFR1-TACC1 fusion gene and methylation profiling suggested the molecular diagnosis of EVN. The representative case was an "intraventricular" neurocytoma displaying molecular features of an "extraventricular" neurocytoma. Clinicopathological and molecular definitions have collided in our case and raised questions about the current definition of CN and EVN.

Spinal leptomeningeal hemangioblastomatosis occurring without craniospinal surgery in von Hippel-Lindau disease

Hemangioblastomatosis represents an unusual and malignant leptomeningeal dissemination of hemangioblastoma (HB). It has been reported in patients with sporadic HB or von Hippel-Lindau (VHL) disease. Hemangioblastomatosis had been reported following resection of a primary HB lesion in all cases except one patient with a sporadic HB. We present a patient with VHL with several HBs at the brainstem, cerebellum, pituitary stalk and retina who developed spinal hemangioblastomatosis without previous craniospinal surgery. A whole spine MRI showed the spinal dissemination from the primary lesions. The patient received craniospinal radiotherapy due to the extensive spinal leptomeningeal dissemination and multiple HBs. MRI performed 12 months after the radiotherapy showed stability of the lesions.

DNA methylation profiling of central nervous system hemangioblastomas identifies two distinct subgroups

Hemangioblastomas (HBs) of the central nervous system are highly vascular neoplasms that occur sporadically or as a manifestation of von Hippel–Lindau (VHL) disease. Despite their benign nature, HBs are clinically heterogeneous and can be associated with significant morbidity due to mass effects of peritumoral cysts or tumor progression. Underlying molecular factors involved in HB tumor biology remain elusive. We investigated genome‐wide DNA methylation profiles and clinical and histopathological features in a series of 47 HBs from 42 patients, including 28 individuals with VHL disease. Thirty tumors occurred in the cerebellum, 8 in the brainstem and 8 HBs were of spinal location, while 1 HB was located in the cerebrum. Histologically, 12 HBs (26%) belonged to the cellular subtype and exclusively occurred in the cerebellum, whereas 35 HBs were reticular (74%). Unsupervised clustering and dimensionality reduction of DNA methylation profiles revealed two distinct subgroups. Methylation cluster 1 comprised 30 HBs of mainly cerebellar location (29/30, 97%), whereas methylation cluster 2 contained 17 HBs predominantly located in non‐cerebellar compartments (16/17, 94%). The sum of chromosomal regions being affected by copy‐number alterations was significantly higher in methylation cluster 1 compared to cluster 2 (mean 262 vs. 109 Mb, p = 0.001). Of note, loss of chromosome 6 occurred in 9/30 tumors (30%) of methylation cluster 1 and was not observed in cluster 2 tumors (p = 0.01). No relevant methylation differences between sporadic and VHL‐related HBs or cystic and non‐cystic HBs could be detected. Deconvolution of the bulk DNA methylation profiles revealed four methylation components that were associated with the two methylation clusters suggesting cluster‐specific cell‐type compositions. In conclusion, methylation profiling of HBs reveals 2 distinct subgroups that mainly associate with anatomical location, cytogenetic profiles and differences in cell type composition, potentially reflecting different cells of origin.