MON-121 Adult Sellar Atypical Teratoid/Rhaboid Tumor Mimicking Pituitary Adenoma: A Case Presentation

Abstract Disclosure: J. Lin: None. B. Kleinschmidt-DeMasters: None. C. Turin More: None. Atypical teratoid/rhabdoid tumors (AT/RT) are rare aggressive embryonal central nervous system tumors due to mutations in SMARCB1 or SMARCA4 genes that are well known to occur in children. Far less commonly, they can occur in the sellar region, which is almost exclusively reported in adult women. Both have poor prognosis; timely post-operative chemoradiotherapy has been associated with longer overall survival, mandating expedited diagnosis. Here, we report an example of an adult sellar AT/RT thought preoperatively to be a nonfunctioning pituitary adenoma. A 50-year-old female with history of stage I granulosa cell carcinoma of the right ovary status post resection and etoposide/carboplatin chemotherapy in 2020 in remission who presented with new onset headache with right facial droop. Magnetic resonance imaging (MRI) showed a prominent pituitary gland. Headache initially improved with course of high dose dexamethasone. A month later, she noted right eye ptosis and was found to have complete right third, fourth, and partial sixth nerve palsy. Repeat MRI pituitary showed diffuse enlargement and heterogeneous enhancement of the pituitary gland with probable invasion of the right cavernous sinus. Biochemical evaluation consistent with secondary hypothyroidism, inappropriately suppressed gonadotropins and hyperprolactinemia likely secondary to stalk effect. Given concern for secondary adrenal insufficiency, she was started on prednisone 5mg daily after completion of dexamethasone course. She underwent endoscopic transsphenoidal resection of the pituitary mass. Pathology returned positive for AT/RT. Post-operatively, patient continued to have right eye ptosis and headaches. She was started on levothyroxine due to persistent secondary hypothyroidism. One-week postoperative MRI with residual disease. She was referred to medical and radiation oncology urgently with plan to start radiation therapy with concurrent cisplatin. To date, about 41 cases of adult sellar AT/RT have been reported. Differentiating between malignant pituitary tumor from benign adenoma is difficult without histological evaluation. Pre-operative hormonal levels are nonspecific. Radiographic features often mimic pituitary macroadenomas. Due to aggressive nature of AT/RT tumors, clinical signs may serve as important clues; current literature reviews have shown that these tumors often have rapid progression of symptoms mostly in less than 2 months. Prognosis is poor with an estimated medium overall survival of 23 months. However, longer overall survival has been observed in patients receiving adjuvant chemotherapy post-surgical resection. In conclusion, AT/RT should be included in the differential diagnosis of pituitary tumors especially for those with rapid growth rate and aggressive symptoms to achieve early diagnosis and prompt therapy for optimized survival rate. Presentation: Monday, July 14, 2025