Primary central nervous system lymphoma involving the hypothalamic-pituitary axis presenting with hypopituitarism: A case report with long-term follow-up.

Primary central nervous system lymphoma (PCNSL) involving the hypothalamic-pituitary axis is a rare condition and may present with nonspecific neurologic and endocrine signs, often mimicking more common sellar lesions. We report the case of a 59-year-old woman admitted with subacute behavioral changes, cognitive decline, and polyuria. Magnetic resonance imaging revealed a pituitary-infundibular mass with suprasellar extension and marked bifrontal edema. Endocrine evaluation demonstrated panhypopituitarism and arginine vasopressin deficiency. The clinical course was complicated by severe dysnatremias requiring intensive care management and hormonal replacement. Histopathologic analysis of a transsphenoidal biopsy confirmed diffuse large B-cell lymphoma, with no systemic disease on PET-CT or bone marrow evaluation. The patient was treated with the MATRix chemotherapy regimen followed by autologous stem cell transplantation, achieving sustained complete remission at 3.5 years. Persistent hypogonadotropic hypogonadism remained as a sequelae. This case underscores the diagnostic challenges of sellar involvement by PCNSL and highlights the importance of including lymphoma in the differential diagnosis of hypothalamic-pituitary masses. Acute pituitary failure with severe electrolyte disturbances may precede oncologic diagnosis, and early multidisciplinary management combined with aggressive therapy can result in long-term remission.