8637 Pituicytoma mimicking Craniopharyngioma

Abstract Disclosure: O. Araoye: None. T. Delibasi: None. A. Chaugule: None. S.K. Dhillon: None. C. Fuller: None. Pituicytoma, a rare low-grade glial tumor originating from the neurohypophysis or infundibulum of the pituitary gland, poses diagnostic challenges due to its propensity to mimic other sellar or suprasellar lesions. We present a case of a 51-year-old male with a history of a suprasellar mass initially suggested to be a craniopharyngioma, incidentally discovered. Opting for elective surgery, the patient underwent transsphenoidal resection, revealing a highly vascular tumor adherent to the optic chiasm and pituitary stalk. While the tumor was successfully removed, sacrifice of the pituitary stalk led to postoperative complications, including cerebrospinal fluid (CSF) leak and central diabetes insipidus (DI).Histopathological examination characterized the tumor as oncocytic pituicytoma/spindle cell oncocytoma, a subtype of pituicytoma. The anti-mitochondrial antibody staining at an external laboratory displayed diffuse granular cytoplasmic staining supporting oncocystic pituicytoma/spindle cell oncocytoma.Postoperatively, the patient developed central DI treated initially with desmopressin (DDAVP), complicated by subsequent hyponatremia necessitating salt tablets and fluid restriction. Additionally, central adrenal insufficiency was managed with hydrocortisone, and central hypothyroidism with levothyroxine. A history of testosterone deficiency was addressed through testosterone injections every 10 weeks.Pituicytoma's diagnostic complexity arises from nonspecific radiological features, requiring reliance on histology and immunohistochemistry for definitive diagnosis. The expression of TTF1 emerges as a characteristic marker. Surgical resection, the primary treatment modality, proves curative in most cases, albeit with associated morbidity including CSF leak, DI, and panhypopituitarism. The role of adjuvant radiotherapy remains uncertain, potentially considered in cases of incomplete resection or recurrence.This case emphasizes three key aspects: first, the potential misdiagnosis of a lobulated suprasellar mass as craniopharyngioma when it could be pituicytoma; second, the development of postoperative DI due to pituitary stalk involvement; and third, the importance of considering pituicytoma in the differential diagnosis of sellar and suprasellar masses.In conclusion, pituicytoma, though rare, demands a nuanced diagnostic approach and comprehensive postoperative management to address potential complications and optimize patient outcomes. Presentation: 6/2/2024