Malignant Rhabdoid Tumors of Cranial Nerves-A Clinically Distinct Group With Characteristic Neuroradiological, Histopathological, and Molecular Features.

Background: Malignant rhabdoid tumors occasionally develop along cranial nerves, but clinical, histopathological, and molecular features have not been examined in larger series.

Methods: We retrospectively interrogated data from the European Rhabdoid Registry, EU-RHAB, to identify malignant rhabdoid tumors affecting cranial nerves. We retrieved clinical information and reviewed magnetic resonance imaging (MRI) data. Furthermore, histopathological review and molecular profiling were performed.

Results: Among 425 patients, we identified a total of 14 harboring malignant rhabdoid tumors with cranial nerve involvement. Median age at diagnosis was 28 months (range: 0-13 years). Various cranial nerves were affected, the trigeminal nerve (n = 4) and the facial and/or vestibulocochlear nerve (n = 5) being most frequently involved. In most cases, the initial clinical and neuroradiological suspicion was schwannoma. Neuroradiology review of magnetic resonance imaging studies confirmed a tumor along the cranial nerve, but signal characteristics with restricted diffusion were rather suggestive of a malignant tumor of high cellularity. Histopathological examination, using among others neurofilament staining confirmed the diagnosis and infiltration of nerve fascicles. DNA methylation profiles demonstrated high similarity with ATRT-MYC as well as extracranial malignant rhabdoid tumors (median calibrated scores: 1.00).

Conclusions: Malignant rhabdoid tumors of the cranial nerves represent a small but clinically distinct group, which initially is often not included in the differential diagnoses of pediatric cranial nerve tumors. Restricted diffusion on MRI may provide an early diagnostic clue. Histopathology and molecular signature are characteristic, but the developmental origin of malignant rhabdoid tumors of the cranial nerves remains to be determined.