A Biphasic Presentation of Diffuse Large B-cell Lymphoma Metastasis to the Hypothalamus-pituitary Axis: A Case Report and Literature Review.

The Hypothalamus-Pituitary axis (HPA) is a rare location for metastasis of non-Hodgkin's lymphoma. Lymphomas constitute less than 0.5% of reported HPA metastasis. This case is unique in that, in addition to the noted panhypopituitarism; initial diagnostics demonstrated marked hyponatremia, consistent with syndrome of inappropriate antidiuretic hormone (SIADH), which was subsequently complicated by sudden diabetes insipidus (DI), suggesting hypothalamic/stalk infiltration. Despite low sensitivity, CSF cytology/flow cytometry may serve as a less invasive diagnostic measure. Treatment includes systemic chemotherapy with agents that cross the blood-brain barrier. Surgical resection alone or associated radiotherapy did not show an increase in survival. The prognosis remains poor.