We present a series of nonectopic pituitary adenomas presenting as polypoid sinonasal or nasopharyngeal masses. Thirteen cases diagnosed by biopsies from the nasal cavity, sinuses, or nasopharynx were identified from a series of 1288 surgical pituitary specimens. The patients included 5 men and 8 women ranging from 29 to 69 years of age. The presentations included nasal obstruction (4 cases), headaches (3), visual defects (2), recurrent nose bleeds (1), rhinorrhea (1), sepsis (1), fatigue (1), and hyperthyroidism (1). All patients had large tumors involving the sella and extending inferiorly to involve the sphenoid sinus in 10 cases, ethmoid in 8, nasopharynx in 3, nasal cavity in 6, maxillary and frontal sinuses in 1 case each. In 3 patients, the biopsy was from the nasopharynx, in 4 from the nasal cavity, in 4 from the sphenoid sinus, and in 2 from the ethmoid sinus. The correct diagnosis of pituitary adenoma was initially made in 10 cases. In 3 cases the initial diagnosis was incorrect; 2 tumors were classified as olfactory neuroblastoma, one of those was reclassified as neuroendocrine carcinoma, and 1 case was initially diagnosed as neuroendocrine carcinoma with aberrant adrenocorticotrophic hormone expression. Clinical follow-up (2 to 25 y) and treatment information was available in 10 cases. All 10 patients were alive, either free of disease (4 cases) or with disease (6 cases). In 2 cases, the wrong diagnoses led to incorrect treatment with significant morbidity. These cases illustrate that pituitary adenomas can invade nasopharynx and sinonasal cavities and when they do, they present a possible diagnostic pitfall with potentially serious consequences. We demonstrate the need to always consider this entity when encountering a nasopharyngeal or sinonasal tumor with neuroendocrine features.