Sinonasal Undifferentiated Carcinoma (SNUC), from the CureRays guide library.

Sinonasal undifferentiated carcinoma is a rare, fast-growing cancer of the nasal cavity and sinuses that is treated aggressively by combining chemotherapy, radiation, and surgery, with radiation a central part of cure because of its delicate location near the eyes and brain.

What it is.

Sinonasal undifferentiated carcinoma (SNUC) is a rare and aggressive cancer that arises in the nasal cavity and paranasal sinuses. Under the microscope its cells look very primitive ('undifferentiated'), meaning they have lost the features that would show what tissue they came from, which is part of why it grows quickly. Because it sits close to the eyes, the base of the skull, and the brain, it can grow into these structures and often causes a blocked nose, nosebleeds, facial pain or pressure, or vision changes, and it is frequently advanced when found. Treatment is intensive and team-based, typically combining chemotherapy, radiation, and surgery. Modern approaches that start with chemotherapy to shrink the tumor have improved outcomes, and care is best delivered at experienced centers.

How radiation treats it.

Radiation damages the DNA inside cancer cells so they can no longer grow and divide, which is especially effective against fast-dividing tumors like SNUC. Because the cancer sits next to the eyes, optic nerves, and brain, radiation must be shaped very precisely; intensity-modulated radiation and proton therapy concentrate the dose on the tumor while sparing vision and brain function. Radiation is usually combined with chemotherapy — which makes the radiation more effective — and is delivered after or instead of surgery depending on the plan. Treatment is painless during delivery, given over several weeks of daily sessions, and external-beam radiation leaves no radioactivity in the body.

The ways we can treat it.

Intensity-modulated radiation (IMRT). Beams are sculpted around the eyes, optic nerves, and brain to deliver a high tumor dose while protecting vision and brain tissue.

Proton therapy. Proton beams stop at a chosen depth and spare tissue beyond the target, helping limit dose to the brain and eyes in this delicate region.

Concurrent chemoradiation. Radiation is paired with chemotherapy so the two together damage the fast-dividing cancer cells more effectively than either alone.

Questions we hear often.

Why is treatment so intensive? SNUC grows quickly and is usually advanced when found, often pressing against the eyes, skull base, or brain. Combining chemotherapy, radiation, and sometimes surgery gives the best chance of controlling it, which is why care is aggressive and team-based from the start.

Will my vision be affected? It can be, because the cancer and its treatment involve the area around the eyes. Teams use precise radiation techniques such as IMRT and proton therapy specifically to protect the eyes and optic nerves while still treating the tumor effectively. Your doctors will discuss the individual balance of risks.

Does the exact diagnosis matter? Yes. Several rare sinonasal cancers can look like SNUC under the microscope. Modern molecular testing can distinguish true SNUC from related tumors (such as NUT or SMARCB1-deficient carcinoma), and the precise diagnosis can change the recommended treatment — so expert pathology review is important.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.