Unfortunately your son has had a pathology report dx ASPS in his sinuses , however I hope there is further discussion and investigation to the "growing" sinus tumor. I agree with everthing but the biopsy as I know you do too, Deb.
http://care.american-rhinologic.org/sinus_tumorsEvaluation and diagnosis
Evaluation of patients with nasal symptoms is often performed by an otolaryngologist and involves taking a complete medical history, performing an examination of the head and neck region, and often nasal endoscopy of the nasal and sinus areas (looking inside the nose with a small scope). If there is any concern for a tumor (mass or growth), imaging studies are performed and may include CT scan, MRI scan and in certain situations PET-CT scan. If a tumor is suspected, a biopsy is typically performed to determine exactly what sort of growth is present. A biopsy involves taking a small sample of the tissue of the nose, and this can be done either in the clinic or the operating room depending on the circumstances. A biposy is important since there are a number of different types of sinus and nasal tumors, and many are treated differently.