SAT-092 - An Uncommon Cause of A Sellar Mass: Metastatic Pituitary Lymphoma

Background: Most sellar masses are pituitary adenomas; however, rare etiologies such as lymphoma must be considered. Metastatic lymphoma to the pituitary is very rare comprising 0.5% of pituitary metastasis. Early recognition is critical, as management and prognosis differ significantly from those of pituitary adenomas.

Case: A 58-year-old female with a history of hyperlipidemia presented to the hospital with three weeks of dizziness, blurred vision, and headaches. Ophthalmologic evaluation revealed binocular diplopia but no hemianopsia. Brain MRI with and without contrast demonstrated an intrasellar mass extending into the right cavernous sinus with encasement of the right cavernous carotid artery, concerning for an invasive pituitary macroadenoma. She denied galactorrhea, changes in shoe size or ring size, fevers, or night sweats. She endorsed a 10-pound weight loss in the last month.

Comprehensive endocrine evaluation was unremarkable. ACTH 24.3 pg/mL, 8 am cortisol 13.7 µg/dL, TSH 2.54 mIU/L, free T4 1.10 ng/dL, IGF-1 196 ng/mL, alpha-subunit 1.1 ng/mL, appropriate menopausal-range FSH (50.2 mIU/L) and LH (28.1 mIU/L), and serum prolactin 26.8 ng/mL with dilution studies excluding hook effect. Overall, workup was consistent with a nonfunctioning sellar mass. Transsphenoidal biopsy revealed diffuse large B-cell lymphoma. Subsequent whole-body CT demonstrated systemic involvement with pulmonary mass lesions, aortocaval and iliac lymphadenopathy. The patient was initiated on R-EPOCH chemotherapy (rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin), along with intrathecal methotrexate.

Discussion: Metastatic lymphoma to the pituitary most commonly presents with pituitary insufficiency, including anterior hypopituitarism and diabetes insipidus, and may be associated with hyperprolactinemia due to stalk involvement. Common neurologic symptoms include headache and diplopia, which were both present in our patient. MRI features such as homogeneous enhancement, suprasellar extension, and infundibular involvement are atypical for pituitary adenomas and should raise suspicion for lymphoma. Prompt recognition is essential, as treatment requires systemic chemotherapy rather than surgical debulking. Prognosis is often poor in these patients as metastasis to the pituitary is a marker of advanced disease.

Conclusion: This case highlights the importance of maintaining a broad differential diagnosis for pituitary masses. Lymphoma with metastasis to the pituitary, though rare, should be considered when a sellar mass is found on imaging, particularly when imaging features and clinical presentation are atypical for pituitary adenoma.

References:
Tovar-Méndez VH, Cuenca D, Gómez-Pérez FJ, Cuevas-Ramos D. Pituitary Infiltration by Lymphoma. J Endocr Soc. 2022;6(12):bvac161. Published 2022 Oct 27. doi:10.1210/jendso/bvac161

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