SUN-431 Primary CNS Lymphoma Involving the Hypothalamus and Pituitary Gland in an Immunocompetent Host Causing Panhypopituitarism

Background: Primary isolated hypothalamic CNS lymphomas in immunocompetent hosts are rare, and the associated presentation of multiple anterior pituitary deficiencies and central diabetes insipidus has been described in 4 cases. Case Report: A 70-year-old man presented with several weeks of progressively worsening fatigue, nausea, vomiting and lethargy. Thyroid function tests obtained by his primary care provider were notable for a TSH 0.14 mU/L (0.35-4.94 mU/L) and free T3 3.4 (4.0-12.8 pg/mL). These abnormal results prompted a brain MRI to be obtained, which revealed a homogenously enhancing mass in the hypothalamus extending bilaterally, 24 x 18 x 16 mm in size. The patients was hospitalized for worsening symptoms and hypotension; left upper lid ptosis was noted on examination, as well. Laboratory tests were notable for a Na(+) 139 mmol/L (136-144 mmol/L), K(+) 4.0 mmol/L (3.5-5.0 mmol/L), glucose 80 mg/dL (64-128 mg/dl), cortisol 2.4 (0.0-9.0 ug/dL at 2000 hrs), ACTH 5 pg/mL (7-69 pg/mL), TSH 0.56 mU/L (0.35-4.94 mU/L), Free T4 0.5 ng/dL (0.8-1.7 ng/dL), FSH 0.7 IU/L (1.5-12.4 IU/L), LH 0.1 IU/L (1.7-8.6 IU/L), GH 0.73 ng/mL (0.05-3.0 ng/mL), IGF-1 61 ng/mL (27-246 ng/mL) and ACE level 51 U/L (9-67 U/L). HIV and Hepatitis B serology were both negative. He was treated with hydrocortisone 50 mg q8h with rapid improvement in blood pressure and symptoms. He underwent endoscopic brain biopsy with pathologic examination indicating B cell lymphoma was present. There was insufficient tissue sample for flow cytometry. PET/CT was negative for other hyper-metabolic lesions. Subsequent bone marrow biopsy showed normal marrow with trilineage hematopoiesis; there was no morphological or flow cytometric evidence of hematological or distant malignancy including lymphoma. He was discharged from the hospital with hydrocortisone 20 mg in the morning and 10 mg in the afternoon, Levothyroxine 88 mcg daily, and desmopressin 50 mcg inhaled daily. He received treatment with high-dose methotrexate, rituximab and temozolomide. Brain MRI after 2 cycles of chemotherapy showed complete resolution of the mass. The ptosis of the left eye remained unchanged, and the patient remains on hydrocortisone, levothyroxine and desmopressin. Conclusion: Although primary CNS lymphomas are rare in immunocompetent persons, and are particularly rare when presenting in the hypothalamus and pituitary gland, they should be considered in persons presenting with concurrent anterior and posterior pituitary deficiencies. Other important differential diagnoses of simultaneous anterior and posterior pituitary deficiencies with simultaneous hypothalamic and pituitary lesions include malignancies such as craniopharyngioma, metastatic melanoma, renal cell carcinoma and germ cell tumors; and infiltrative diseases such as sarcoidosis, IgG4-related hypophysitis, amyloidosis, and hemochromatosis.