THU106 Malignant Epithelioid Neoplasm As The Cause Of A Rapidly Growing Pituitary Mass

Disclosure: S. Riahi: None. S.S. Chaidarun: None. Background: Malignant epithelioid neoplasm is a rare cause of a pituitary mass, and should be kept on the differential whenever evaluating patients with evidence of rapid pituitary enlargement. Clinical Case: A 43 year-old man presents with 3-month history of worsening severe headaches, decreased libido, erectile dysfunction, polydipsia, polyuria (6L/day) with nocturia every hour, and fatigue. He also noted some blurry vision without loss of his peripheral vision. MRI of the brain showed a 1.5cm mass in the sellar and suprasellar region abutting the optic chiasm. Of note, he had a brain MRI performed 18 months prior for vertigo which did not demonstrate any mass in the pituitary. He presented to the endocrinology office for evaluation. His laboratory tests demonstrated mildly elevated prolactin 31.2 ng/mL (n 4.0-15.2), and findings consistent with panhypopituitarism and central diabetes insipidus, including low FT4 of 0.46 ng/dL (n 0.93-1.70), FSH 0.7 mIU/mL (n 1.5-12.4), an undetectable LH (n 1.7-8.6mIU/mL), random cortisol of 1mcg/dL (n 4.8-19.5) ACTH 6.2 pg/mL (n 7.2-63), IGF-1 of 139 ng/mL (n 44-275), total testosterone undetectable (n 240-950 ng/dL), sodium 144mmol/L (n 135-145) with low urine specific gravity 1.008 and urine osmolality of 143mOsm/Kg (n 60-1200). HCG was undetectable (n 0-2mIU/mL) but LDH was elevated at 313 unit/L (n 110-220). He was started on corticosteroids, levothyroxine, DDAVP, and referred to neurosurgery. Specimens from his transphenoidal biopsy demonstrated findings consistent with a malignant epithelioid neoplasm. Further analysis and genetic testing is still pending. He has been referred to oncology service for further management and care. Conclusion: A rapidly growing symptomatic pituitary mass with central diabetes insipidus should raise suspicion for malignant etiology beyond the more prevalent pituitary adenoma. Malignant epithelioid neoplasm are uncommon tumors of the brain, however they are known to be aggressive tumors with high mortality. Treatment commonly includes some combination of surgery, radiotherapy, and chemotherapy(1). Reference: (1) Jog AP, Ronderos DM, Ali A, Niazi M, Diaz-Fuentes G. Malignant Epithelioid Neoplasm of the Brain. Cureus. 2020 Aug 27;12(8):e10079. doi: 10.7759/cureus.10079. PMID: 33005505; PMCID: PMC7523542. Presentation: Thursday, June 15, 2023