FRI317 Simultaneous Occurrence Of A Pineal Germ Cell Tumor And Pituitary Macroprolactinoma In A Young Male

Disclosure: E.P. Monsour: None. S. Badour: None. J.M. Munoz Pena: None. W.T. Donahoo: None. Background: Germ Cell Tumors (GCTs) are a group of heterogeneous tumors that derive from pluripotent germ cells and originate in the yolk sac of the embryo in early gestation. They account for 10% of all central nervous system (CNS) GCTs, primarily occurring in the pediatric and adolescent populations. The co-existence of macroprolactinoma and a mixed CNS GCT is extremely rare, with an unknown worldwide prevalence. Here we report a case of a pituitary macroprolactinoma occurring with a separate primary CNS mixed GCT. Clinical Case: A 19-year-old male presented with a 2-month history of headaches associated with nausea and vomiting. Relevant physical exam findings included decreased visual acuity, absent facial and axillary hair, and prominence of the left testis. Brain MRI demonstrated a pituitary adenoma measuring 3.5 x 2.3 x 3.2 cm extending into the cavernous sinus and an enhancing necrotic lesion in the third ventricle measuring 5.0 x 3.7 x 4.9 cm. Testicular ultrasound revealed two sub-centimeter ill-defined masses in the left testis. Pre-operative labs showed intact thyroid, adrenal, and growth hormone axis. He had a low total testosterone [14.2 ng/dl, reference range (RR): 230-800 ng/dL] with inappropriately normal gonadotrophins and markedly elevated prolactin (PRL) level (2,517 ng/mL, RR <14 ng/mL). Testicular tumor marker, alpha-fetoprotein, was elevated (15.3 ng/dL, RR <9 ng/dL). He was started on glucocorticoids for vasogenic edema and cabergoline twice weekly. He underwent left orchiectomy and subsequent pineal tumor resection. Testicular tumor pathology was consistent with teratoma and a well-differential neuroendocrine tumor with negative margins. Pineal tumor pathology was diagnostic of a mixed GCT. Despite optimal medical therapy, the patient ultimately opted to pursue transsphenoidal tumor resection. Pituitary mass pathology was compatible with a pituitary adenoma, immunoreactive for PRL. Post-operative PRL levels decreased to 6 ng/dL. He achieved a surgical cure without the need to restart dopamine agonist therapy. Conclusion: Simultaneous occurrence of primary brain tumors with different pathologies is estimated to be ∼0.9% of all brain tumors. To our knowledge, only one other case report described an adolescent with a craniopharyngioma and intracranial GCT. This is the first report in the literature of a pituitary macroprolactinoma synchronous with a mixed CNS GCT, and testicular well-differential neuroendocrine tumor with teratoma. Presentation: Friday, June 16, 2023