LBMON135 Diffuse Large B-cell Lymphoma Affecting The Pituitary Gland: A Case Report

INTRODUCTION: Diffuse large B-cell lymphoma is a common manifestation of non-Hodgkin lymphoma, representing approximately 25% of non-Hodgkin lymphoma cases. Patients typically present with an enlarging lymph node that is painless and associated with constitutional symptoms. For the pituitary to be involved is extremely uncommon with approximately 10 previously reported cases. We present a 51-year-old Caucasian female who initially presented with nausea, vomiting, polyuria, and polydipsia and was found to have a pituitary mass diagnosed as diffuse large B-cell lymphoma upon surgical resection. CASE PRESENTATION: A 51-year-old female presented with nausea, vomiting, polydipsia, and polyuria. She had no history of lithium use. She was found to have an initial serum osmolarity of 324 mOsm/kg (280-300mOsm/kg), urine sodium of <20mmol/L, and urine osmolality of 191 mOsm/kg (390-1,090 mOsm/kg). She was initially diagnosed with primary polydipsia, however, her symptoms did not improve with appropriate treatment. An MRI was performed demonstrating a 13mm lobulated, homogeneously enhancing hypothalamic mass with adjacent thickening of the pituitary stalk and pituitary. Subsequent lab work demonstrated deficiencies in ACTH, TSH, cortisol, FSH, LH, and GH. She was initiated on DDAVP, levothyroxine, and hydrocortisone. A repeat MRI several months later revealed that the pituitary mass had enlarged to 2.4cm×2.3cm×1.5cm. She underwent surgical removal of the mass via right frontal craniotomy, and histopathology demonstrated diffuse large B-cell lymphoma. She underwent chemotherapy with high dose methotrexate and cytarabine for 3 cycles. Subsequent MRIs demonstrated stable intracranial findings. Her pituitary function did not recover, and she remains on hormonal replacement with levothyroxine, hydrocortisone, and desmopressin. The patient continues to follow with endocrinology and oncology in the outpatient setting. CONCLUSION: This is a rare instance of diffuse large B-cell lymphoma affecting the pituitary gland. In a patient presenting with symptoms of diabetes insipidus, it is prudent to evaluate for other signs of pituitary involvement. This patient was found to have a pituitary mass on MRI that did not have an appropriate response to medical therapy. Thus, surgical management was performed, and histopathology elucidated the etiology of her symptoms. Reference: Kenchaiah, M., Hyer, S. L. Diffuse large B-cell non Hodgkin's lymphoma in a 65-year-old woman presenting with hypopituitarism and recovering after chemotherapy: a case report. J Med Case Reports 5, 498 (2011). https://doi.org/10.1186/1752-1947-5-498 Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.