非機能性下垂体腺腫との鑑別が困難であった下垂体原発悪性リンパ腫

Primary Pituitary Malignant Lymphoma that was Difficult to Differentiate from Nonfunctioning Pituitary Adenoma:A Case Report

Ⅰ．はじめに

　中枢神経系原発悪性リンパ腫（primary central nervous system lymphoma：PCNSL）は，本邦では全原発頭蓋内腫瘍の3.1%を占め⁸⁾，ここ20年間で増加している⁴⁾．しかし，下垂体原発悪性リンパ腫（以下，下垂体リンパ腫）の報告は0.1%と稀である¹⁰⁾．今回，われわれは非機能性下垂体腺腫との鑑別が難しかった下垂体リンパ腫の症例を経験したので，文献的考察を加えて報告する．

　We report a rare case of primary pituitary lymphoma in a 75-year-old immunocompetent woman. The patient was blind in the right eye and presented with visual disturbance in the left eye that started 2 months previously. She also exhibited right third and fifth cranial nerve palsy. Magnetic resonance imaging（MRI）revealed an intrasellar mass lesion with right cavernous sinus invasion and suprasellar extension with compression of the optic chiasm. The mass lesion was isointense on both T1WI and T2WI, and showed less enhancement than a normal pituitary gland on gadolinium-enhanced T1WI. We therefore suspected the tumor to be a nonfunctioning pituitary adenoma. The patient underwent endoscopic endonasal transsphenoidal surgery. The tumor was firm and grayish, and had an ill-defined border along the normal pituitary gland. Histological examination revealed a malignant CD5-positive diffuse large B-cell lymphoma. After surgery, the patient received both chemotherapy and radiotherapy. Although the visual acuity of the right eye did not improved, other symptoms improved. At the 34-month follow-up, no recurrence was detected on serial MRI. Patients with primary pituitary lymphoma often exhibit ophthalmoplegia and/or panhypopituitarism more frequently than expected from radiological findings. In cases of pituitary tumors with atypical symptoms, a biopsy and general physical examination should be performed immediately to determine the diagnosis and perform adjuvant therapy even when the tumor is assumed as nonfunctioning pituitary adenoma from the image findings.