Atypical teratoid rhabdoid tumour in the third ventricle of a young adult - a rare presentation.

Introduction: Atypical teratoid/rhabdoid tumours (AT/RT) are malignant CNS tumours predominantly seen in infants and children. Adult AT/RTs have a predilection for mid-line structures, such as the pineal and pituitary glands. We report a case of AT/RT in a young adult, with its origin from the third ventricle. This is the first documented case of adult AT/RT in the third ventricle.

Case presentation: A 20-year-old male presented with acute onset headache and vomiting. MRI showed a lesion involving the optic chiasm, hypointense on T1, and heterogeneously hyperintense on T2, with stippled post-contrast enhancement. He underwent a right peri-coronal parasagittal craniotomy, transforaminal and sub choroidal approach with gross total tumour resection. Histopathological report was ATRT, WHO grade 4, with loss of SMARCB1 (INI1) protein. He later underwent a ventriculo-peritoneal shunt placement for postoperative hydrocephalus and was later given adjuvant chemoradiotherapy. No recurrence was noted on follow up MRI.

Conclusion: AT/RTs are not limited to the paediatric age group, and their incidence among adults is being increasingly reported. Occurrence of AT/RT in the third ventricle of a young adult male has never been reported in the past. It merits consideration as a differential diagnosis of any midline lesion with malignant appearance in adults.