Primary diffuse leptomeningeal atypical teratoid/rhabdoid tumours (ATRT) of childhood: a molecularly characterised case report and literature review.

Background: Atypical teratoid/rhabdoid tumours (ATRTs) are malignant central nervous system tumours, typically presenting in the posterior fossa of very young children. Prognosis remains poor despite current therapy, while tumorigenesis implicates both genomic and epigenetic dysregulation. Primary diffuse leptomeningeal (PDL) ATRT, characterised by the absence of an intraparenchymal mass lesion, is seldom reported but appears associated with a dismal outcome.

Case Presentation: We describe a 7-year-old male presenting with a PDL MYC-subgroup ATRT. The patient received multimodal upfront therapy, including high-dose craniospinal radiotherapy, embedded within a chemotherapy backbone. An unexpected clinical and radiological improvement was also observed upon cessation of all therapy for presumed disease progression. Although the patient eventually succumbed to the disease at 30 months, he demonstrated the longest survival for any PDL ATRT patient reported (median 8 months).

Conclusion: Exhaustive literature review identified seven preceding published cases of PDL ATRT. Ours is the only one to have molecular subgrouping assigned. Perfusion imaging, within a multi-parametric diagnostic package, may be a sensitive marker for malignancy against other aetiologies in challenging presentations. Acknowledging the scarcity of the entity, we cautiously suggest a combination of chemotherapy and upfront high-dose craniospinal radiotherapy, if appropriate, may prolong survival for older children with PDL ATRT compared to exclusive chemotherapy or focal irradiation-based strategies. Our patient's recovery during palliation following a radiological diagnosis of disseminated relapse highlights the importance of confirming disease recurrence by tissue extraction where feasible.