Intrasellar malignant lymphoma developing within pituitary adenoma.

A mixed lymphoblastic T cell lymphoma and gonadotroph cell pituitary adenoma occurred 25 years after first resection of the adenoma. Within 1 year the lymphoma overgrew the adenoma, but was still restricted to the sellar region. Histologically, lymphoma and adenoma components were tightly admixed. Possible pathogenetic pathways for intra-adenomatous lymphoma development include monoclonal expansion of T cell infiltrates, expression of adhesion molecules specific for adenoma endothelium, and production of mitogenic pituitary hormones.