8719 Epidermal Inclusion Cyst Masquerading as Obstructive Craniopharyngioma

Abstract Disclosure: M. Murugesh: None. F. Thelmo: None. J. Watari: None. The most common cause of a sellar mass is notably pituitary adenoma (84.6%), followed by craniopharyngioma (3.2%), cystic nonneoplastic lesion (2.8%), inflammatory lesion (1.1%), meningioma (0.94%). Epidermoid cysts are benign congenital inclusion cysts that can occur anywhere in the body, with about 7% percent occurring in the head and neck region. Very rarely, they can present intracranially, accounting for about 0.3-1.8% of primary tumors. We present a rare case of epidermoid cyst growing as a suprasellar mass causing hypopituitarism.A 58-year-old female presented to the emergency department with dizziness in the setting of an ear infection. CT head showed 2.8 cm complex suprasellar mass, with adjacent 1 cm nodule at the cerebellopontine angle. MRI showed 2.7 x 2.4 x 2.7 cm suprasellar mass along with “a lobular component along the left posterior aspect extending to the cerebellopontine angle which measures about 1.3 cm, causing mass effect on the midbrain, pons, and optic chiasm”. The differential included craniopharyngioma, macroadenoma and meningioma. Notably, she denied any vision changes. She was evaluated by neurosurgery and after extensive multidisciplinary discussion with ENT and ophthalmology, the patient proceeded with endoscopic surgery for mass resection. Intra-operatively, the mass was noted to be densely adherent to the basilar artery, and sub-total resection was performed. Surprisingly on pathology the mass was identified as an epidermoid cyst, as evidenced by debris with cholesterol clefts and no lesional cells. The patient was started empirically on hydrocortisone 50mg three times a day post-resection. Endocrinology was consulted postoperatively with initial concerns of diabetes insipidus in the setting of hypernatremia, however, the patient’s sodium levels normalized. Pituitary panel at this time was concerning for central hypothyroidism (TSH 0.53 and FT4 0.8) and central adrenal insufficiency (ACTH <9 and AM cortisol 0.9). She was ultimately discharged on prednisone 5mg and levothyroxine 75 mcg with outpatient follow-up. While epidermoid cysts are present in the head and neck region about 7% of the time, they rarely occur in intracranial regions, with about 1.5% of intracerebral epidermoid cysts occurring intracranially. They tend to be slow growing and are often found only when they grow large enough to become symptomatic, as seen in our presented case. Our case highlights the importance of recognizing epidermoid cysts as a rare cause of sellar masses. Presentation: 6/1/2024