Sellar Suprasellar Surprise: A Rare Case of Atypical Teratoid/Rhabdoid Tumor in an Infant

We present a case of a 10-month-old male infant who initially presented with polyuria, polydipsia, drowsiness, and fever. Neuroimaging using non-contrast computed tomography (NCCT) demonstrated obstructive hydrocephalus associated with a suprasellar mass, for which emergency neurosurgical intervention was performed with right parietal medium pressure ventriculoperitoneal (MPVP) shunting. For fever, no cause was found with sterile cerebrospinal fluid (CSF) analysis, and empirical antibiotics were administered. The patient exhibited polyuria with hypernatremia and was diagnosed with arginine vasopressin (AVP) deficiency, further complicated by visual impairment due to left optic atrophy. Hormonal workup revealed secondary hypothyroidism and hypocortisolism. Imaging by contrast-enhanced magnetic resonance imaging (CEMR) revealed a lobulated solid-cystic suprasellar mass with flow void, suggestive of adamantinomatous craniopharyngioma initially. However, despite multiple neurosurgical interventions, the patient's condition deteriorated with recurrent fever and seizures, leading to a revision of ventriculoperitoneal shunts. Repeat CEMR showed an increase in the size of the lesion with spinal leptomeningeal metastasis, suggesting a different pathology. Transventricular biopsy confirmed an atypical teratoid and rhabdoid tumor (AT/RT), World Health Organization Classification of Tumors of the Central Nervous System (CNS WHO) grade 4, characterized by diffuse growth pattern, moderate nuclear pleomorphism, clear cytoplasm, and prominent nucleoli. Immunohistochemistry revealed positive vimentin staining and loss of integrase interactor 1 (INI1) expression, consistent with AT/RT. The patient's parents were counseled on the need for multimodal management, including surgery and chemotherapy. However, due to socioeconomic constraints and a guarded prognosis, they chose to leave against medical advice. This case illustrates the diagnostic challenges in distinguishing AT/RT from other suprasellar masses and emphasizes the importance of a multidisciplinary approach in managing complex pediatric cases.