A 39-year-old man presents to his physician with the complaint of loss of peripheral vision. The subsequent magnetic resonance imaging (MRI) scan below demonstrates

This T1-weighted sagittal MRI scan reveals a dumbbell-shaped homogeneous mass involving the sella turcica and the suprasellar region. This lesion is most consistent with a pituitary adenoma, a benign tumor arising from the adenohypophysis. Pituitary adenomas are the most common sellar lesion and constitute 10-15% of all intracranial neoplasms. Macroadenomas (>10 mm) are generally non secreting tumors. Microadenomas (<10 mm) become clinically apparent from hormonal secretion. They may secrete prolactin (amenorrhea or galactorrhea), growth hormone (gigantism or acromegaly), or ACTH (Cushing syndrome). The tumor pictured is a macroadenoma. Its dumbbell shape results from impingement on the adenoma by the diaphragm of the sella turcica. The suprasellar extension seen here makes a frontal craniotomy rather than a transsphenoidal approach more appropriate.