A sinus bump is a general term for any abnormal growth or swelling found inside the sinuses, the hollow air-filled spaces behind your cheekbones, forehead, and nose. Most sinus bumps are harmless, discovered by accident on a CT or MRI scan done for an unrelated reason. Up to 42.5% of people with no sinus symptoms at all have some kind of visible abnormality in their sinuses on imaging. The type of bump determines whether it needs attention or can simply be left alone.
The Most Common Type: Mucous Cysts
The majority of sinus bumps are small, fluid-filled cysts that form when a mucus-producing gland gets blocked. These appear as smooth, dome-shaped masses, most often sitting on the floor of the maxillary sinus (the large sinus behind your cheekbone). They grow slowly, and their long-term behavior is reassuring: about 60% stay the same size indefinitely, roughly 30% shrink or disappear on their own, and only about 10% get larger over time.
There are two subtypes. True retention cysts have a thin lining of tissue around them, formed by a blocked gland duct. Pseudocysts lack that lining and instead develop when inflammatory fluid pools beneath the sinus membrane. In practice, both look similar on imaging and behave the same way. Neither typically causes symptoms unless it grows large enough to block sinus drainage.
These are different from a mucocele, which is a more aggressive type of cyst that expands and pushes into surrounding structures. Mucoceles generally do require treatment because of their tendency to keep growing and cause damage.
Nasal Polyps
Nasal polyps are soft, painless growths that develop on the lining of the nose or sinuses. They often cluster together, sometimes described as looking like grapes on a stem. Polyps are tied to chronic inflammation lasting more than 12 weeks, and they’re more common in people with asthma, aspirin sensitivity, cystic fibrosis, or persistent allergies.
Small polyps may go unnoticed. Larger ones can block airflow and sinus drainage, leading to congestion, reduced sense of smell, postnasal drip, and facial pressure. If you’ve been dealing with stuffiness and breathing difficulty that won’t resolve, polyps are one of the more likely explanations.
Bone Growths in the Sinus Wall
Osteomas are benign bony bumps that grow from the sinus wall itself. They’re most common in the frontal sinuses (behind the forehead), followed by the ethmoid sinuses (between the eyes), and rarely appear in the cheekbone or sphenoid sinuses. These grow very slowly, roughly 1 millimeter per year in any direction. Many people live with small osteomas and never know it.
Problems arise when an osteoma grows large enough to block a sinus opening, trap mucus, or press on nearby structures. In rare cases, osteomas near the skull base can cause more serious complications, which is why doctors typically monitor them with periodic imaging even when they aren’t causing symptoms.
Dental-Related Sinus Bumps
The roots of your upper back teeth sit very close to the floor of the maxillary sinus, sometimes separated by just a thin shell of bone. A dental infection, a cyst around a tooth root, or even complications from a root canal or dental implant can push into the sinus and create a visible bump from below. These often appear as rounded masses on the sinus floor and can grow surprisingly large without causing obvious sinus symptoms, because the sinus cavity has room to accommodate them before drainage gets blocked.
If a sinus bump traces back to a dental problem, treating the tooth issue usually resolves the sinus finding as well.
Bumps on the Face Over the Sinuses
If you’re feeling an actual lump on the skin of your face rather than seeing something on a scan, the cause is more likely a skin issue than a sinus problem. Keratinous cysts (sometimes called sebaceous cysts) are among the most common. These form when skin cells get trapped beneath the surface, creating a firm, round bump you can usually feel and move slightly with your fingers. They tend to recur in the same spot and can become inflamed periodically. Boils, swollen lymph nodes, and lipomas (fatty lumps) are other possibilities for a bump you can feel on the outside.
How Sinus Bumps Are Found and Identified
Most internal sinus bumps are discovered incidentally. You get a CT scan for headaches, a head injury, or dental planning, and the radiologist spots something in a sinus. This is extremely common. Studies show that between 15% and 37% of CT scans and up to 85% of MRI scans reveal some kind of sinus finding, even in people without symptoms.
CT scans are the primary tool for evaluating sinus bumps because they show bone detail clearly. Radiologists look at specific features to determine what a bump is. Smooth bone remodeling, where the bump gently pushes bone outward without destroying it, suggests something benign and slow-growing. Actual bone destruction, where the bone is eaten away rather than pushed, raises concern for something more aggressive. MRI adds detail about soft tissue and can distinguish between a solid mass, thickened mucosa, and trapped fluid, which all look different on the scan.
A dense, bright spot on CT that sits on the sinus wall is the classic appearance of an osteoma. A smooth, dome-shaped soft tissue mass on the sinus floor is typical of a cyst. Polyps tend to appear as multiple soft tissue densities filling the nasal passages and sinus openings.
When a Sinus Bump Needs Treatment
The deciding factors are symptoms and behavior, not the bump’s mere existence. A small cyst sitting quietly on the sinus floor with no symptoms can be safely ignored. Polyps that block breathing or cause chronic congestion are typically treated first with nasal steroid sprays and, if those don’t work, with a minimally invasive procedure to remove them. Osteomas are monitored and removed only if they grow large enough to cause blockage or complications.
When surgery is needed, it’s usually done endoscopically, meaning a thin camera and instruments are passed through the nostril with no external incisions. Recovery is generally quick, though some swelling and congestion are expected for a week or two afterward. For dental-origin bumps, resolving the underlying tooth problem often eliminates the sinus finding without any sinus-specific procedure.
Symptoms that should prompt a prompt evaluation include persistent one-sided nasal blockage, bloody discharge from one nostril, facial swelling with redness or fever, vision changes, or pain that worsens steadily over days rather than coming and going. These patterns don’t necessarily mean something dangerous, but they warrant imaging to rule out anything beyond a routine bump.