Diagnosis of Sinonasal Ectopic Pituitary Adenomas

Supplemental digital content is available in the text. Abstract Ectopic pituitary adenomas (EPAs) are uncommon sinonasal neoplasms that present a diagnostic challenge in practice. We present a case of a patient presenting with progressive headache. Workup revealed an enhancing mass on magnetic resonance imaging at the anterior clivus with extension into the sphenoid sinus. Resection of the tumor was performed, and microscopic examination showed a neuroendocrine tumor composed of monomorphic cells arranged in nests. The tumor expressed synaptophysin, chromogranin, growth hormone, prolactin, thyroid-stimulating hormone, follicle-stimulating hormone, α-subunit of the glycoproteins, and transcription factors steroidogenic factor 1 and Pit-1, diagnosed as a plurihormonal pituitary adenoma. Given the radiologic and surgical impression of an intact and uninvolved pituitary gland, the lesion was identified as a pituitary adenoma arising in ectopic adenohypophyseal tissue. This case demonstrates the multitude of possible tissue types involved in tumor histogenesis in the sinonasal cavity. We highlight the radiographic, intraoperative, cytologic, and histologic features of sinonasal pituitary adenoma to emphasize the role of an expanded differential, including central nervous system lesions, for neoplasms in this anatomic region.