SAT-100 Brain, B-Cells, and Endocrine Disarray: A Case of Primary CNS Diffuse Large B-CellLymphoma with Panhypopituitarism

Abstract Disclosure: B.D. Cu: None. R. Heinrich: None. J.J. Rossitto: None. Background Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma, characterized by its aggressive clinical course and rapid proliferation. Involvement of the third ventricle, hypothalamus, and pituitary gland by DLBCL is exceedingly rare and poses significant diagnostic and therapeutic challenges. Lesions in these locations can lead to symptoms such as headaches, visual disturbances, and endocrine dysfunctions, including diabetes insipidus and panhypopituitarism. These symptoms arise due to the mass effect and infiltration of the lymphoma into critical neuroendocrine structures. Clinical Case We present a 30-year-old male with recent medical history significant for pre-diabetes, hypothyroidism and sexual dysfunction who presented with ten days of acute progressive right eye changes from blurriness, double vision, to vision loss. He had no preceding events. Labs were significant for: Sodium 148 mmol/L, Adrenocorticotrophic Hormone 4.0 pg/mL, Serum Cortisol (17:00): 1.2 ug/dL, Growth Hormone 0.15 ng/mL, Insulin-Like Growth Factor 1 73 ng/mL (Z score -2.7), Prolactin 34.2 ng/mL, Thyroid Stimulating Hormone 0.03 mU/L, Free Thyroxine 0.6 ng/dL, Total Testosterone by Immunoassay <3 ng/dL, Follicle Stimulating Hormone <0.3 IU/L, Luteinizing Hormone <0.3 IU/L, Cerebrospinal fluid was negative.MRI showed a 2.9 x 1.7 x 2.5 cm avidly enhancing mass within the suprasellar/hypothalamic region along the floor of the third ventricle. Notable anterior optic chiasm displacement and normal pituitary infundibulum, morphology, posterior bright spot. He had a resection of the third ventricular lesion by right frontal craniotomy lamina terminalis approach with the tumor’s location to be immediately after lamina terminalis. His pathology showed Large B Cell-Lymphoma. Treated with Rituximab, Methotrexate, Procarbazine, and Vincristine for eight cycles. Then Thiotepa and Cyclophosphamide for stem cell transplant. After treatment, MRI showed pachymeningeal thickening and enhancements along the floor of the third ventricle that abuts the posterior optic chiasm and pituitary infundibulum without significant mass effect. Conclusion DLBCL with pituitary involvement, although rare, presents significant diagnostic and therapeutic challenges. The pathophysiology of pituitary involvement with DLBCL in the third ventricle is classically relating to infiltrating and/or compressing the hypothalamic-pituitary axis. Research so far has highlighted early diagnosis and a multidisciplinary approach for this condition. However, more research is called for in understanding hypothalamic-pituitary axis recovery. This case highlights the absence of hypothalamic/pituitary radiographic pathology with persistent biochemical evidence of panhypopituitarism and diabetes insipidus in the setting of DLBCL diagnosis, treatment, and now surveillance. Presentation: Saturday, July 12, 2025