Abstract
Primary saddle region tumors are the most commonly pituitary adenomas: They account for more than 90% of all saddle region tumors. Primary central nervous system lymphoma (PCNSL) lesions are relatively rare and are usually found around the ventricles. Reports of PCNSL lesions located in the saddle region are even rarer. We report a rare case of PCNSL originating from the pituitary-pituitary stalk-mammillary body region in a 33-year-old man. Clinical manifestations included progressive endocrine abnormalities and cavernous sinus syndrome. His initial symptoms consisted of fatigue, nausea, vomiting, and diplopia. Endocrine investigations revealed anterior pituitary hypopituitarism, with secondary hypothyroidism, hypogonadism, and adrenal insufficiency. Magnetic resonance imaging (MRI) showed an enhancing lesion in the pituitary stalk and pituitary gland involving the right cavernous sinus, along with loss of the posterior pituitary's T1 hyperintensity. The initial diagnosis at the external hospital was nonbacterial inflammatory pituitary disease. After treatment with methylprednisolone, some symptoms improved, and MRI scans indicated a slight reduction in lesion size. However, the diplopia did not resolve. Two weeks after steroid withdrawal, the patient's symptoms worsened. Upon referral to our hospital, he tested positive for HIV, and follow-up MRI demonstrated lesion enlargement with necrosis and hemorrhagic infarction, as well as reappearance of the posterior pituitary T1 hyperintensity. Following hormone replacement therapy, endoscopic transsphenoidal surgery was performed, and histopathological examination confirmed B-cell lymphoma.