Not What You Expected

Question: A 42 year old female undergoes evaluation for chronic rhinosinusitis. After a failed trial of medical management, surgery is offered and she undergoes a presurgical CT scan for navigation purposes. Upon examining the frontal sinus outflow tract, a lesion isodense to bone is identified emanating from the anterior table, obstructing the right frontal sinus. She has no history of malignancy or radiation therapy, and the remainder of her craniofacial skeleton is normal. What is the most likely diagnosis?

[Answer will be posted with next week's new question]

Answer to last week's question, "A Tight Squeeze?" (November 26, 2018)

Approximately 0.68 mm.