Effect of Temozolomide in a patient with recurring oncocytic gonadotrophic pituitary adenoma

The patient was a 70-year-old man with a recurrent pituitary tumor. Three surgeries were performed but the tumor recurred. Based on histologic, immunohistochemical and ultrastructural studies, the diagnosis of oncocytic gonadotrophic pituitary adenoma was made. The tumor was a macroadenoma partly immunopositive for LH. Immunohistochemistry for O-6 Methylguanine-DNA Methyl-Transferase (MGMT) showed an admixture of immunopositive and immunonegative cells. After recurrence following operations, the patient was treated with Temozolomide, an imidazotetrazine derivative, DNA-alkylating drug. Following Temozolomide administration the MRI demonstrated significant tumor necrosis. A few months later, the patient died of massive pulmonary embolism. No autopsy was performed. The present case indicates that benign, typically slow-growing pituitary adenomas of oncocytic gonadotrophic type may respond to Temozolomide even when the tumor consists of an admixture of MGMT immunopositive and immunonegative cells.