A 71-year-old man with a history of a pituitary prolactinoma and metastatic pancreatic carcinoma presented with epistaxis, visual changes, bilateral ophthalmoplegia, involuntary closure of the left eye, and ptosis of the right eye. The patient was found to have a soft-tissue mass in the posterior nasal cavity with extension through the floor of the sella turcica, the sphenoid sinuses, cavernous sinuses, and suprasellar region. The patient was subsequently taken to the operating room. Intraoperative frozen section of the sinonasal mass demonstrated carcinoma. The final pathology of the mass revealed sinonasal undifferentiated carcinoma (SNUC)-the patient's second skull base lesion and third primary neoplasm. SNUC is a rare neoplasm of the sinonasal cavities that rapidly progresses from symptom onset to mortality in the presence of aggressive multidimensional therapies. Given its poor prognosis and possibly devastating treatments, an open discussion of treatment options between physicians and the patient is of the utmost importance. Although SNUC is rare, it is important that practicing otolaryngologists, neurosurgeons, and skull base surgeons be familiar with this disease process-especially when caring for patients with a history of a benign skull base neoplasm and concern for possible recurrence, as was the case in this report.