Non-Intestinal-Type Sinonasal Adenocarcinoma: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
July 10, 2026

Non-intestinal-type sinonasal adenocarcinoma (SNAC) is a rare type of head and neck cancer that arises from the gland-forming cells lining the nasal cavity or paranasal sinuses, such as the ethmoid or maxillary sinuses. The paranasal sinuses are air-filled spaces in the bones around the nose. This tumor is called “non-intestinal-type” because, under the microscope, the cancer cells do not resemble intestinal cells, which sets it apart from a related tumor called intestinal-type sinonasal adenocarcinoma. Pathologists divide non-intestinal-type SNAC into low- and high-grade tumors, and grade is one of the most important factors in predicting tumor behavior. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes non-intestinal-type sinonasal adenocarcinoma?

At present, doctors do not know the cause of most cases of non-intestinal-type sinonasal adenocarcinoma. Unlike some other sinonasal cancers, it is not clearly linked to workplace dust exposure. A small number of tumors have been associated with human papillomavirus (HPV), but this virus is not believed to cause most non-intestinal-type SNACs.

What are the symptoms?

The symptoms of non-intestinal-type sinonasal adenocarcinoma depend on the size and location of the tumor. Common symptoms include a blocked or stuffy nose, frequent nosebleeds, facial pain or pressure, a decreased sense of smell, and nasal drainage. If the tumor grows toward the eye socket, it may cause swelling around the eye or changes in vision. Because these symptoms overlap with common, noncancerous conditions such as sinus infections, the diagnosis often requires a biopsy and additional testing before it is made.

How is the diagnosis made?

The diagnosis of non-intestinal-type sinonasal adenocarcinoma is made after a tissue sample is examined under the microscope by a pathologist. The sample is usually obtained through a biopsy, in which a small piece of the tumor is removed, often through the nose using an endoscope. The diagnosis can also be made after the entire tumor is removed in a procedure called a resection.

Under the microscope, non-intestinal-type sinonasal adenocarcinoma consists of gland-forming cells that do not resemble intestinal cells. To help confirm the diagnosis and rule out other tumors that may appear similar, the pathologist may perform immunohistochemistry, a test that uses labeled antibodies to detect proteins in tumor cells. The tumor cells in non-intestinal-type SNAC are usually positive for a group of proteins called cytokeratins, including CK7. Very rarely, the tumor cells are positive for CK20, a protein normally seen in cells of the gastrointestinal tract. High-grade tumors may also produce proteins made by neuroendocrine cells, such as chromogranin and synaptophysin. Once the diagnosis is confirmed, imaging studies such as CT and MRI are used to determine the size of the tumor and whether it has spread to nearby structures.

Histologic grade

Pathologists divide non-intestinal-type sinonasal adenocarcinoma into two grades, low and high, based on how the tumor cells look under the microscope. The grade is important because it predicts how the tumor is likely to behave and helps guide treatment decisions.

Low grade — The tumor is made up of medium-sized cells that contain a specialized protein called mucin. The cells often connect to form round, gland-like structures or long finger-like projections called papillae, and the glands may be arranged back-to-back in a pattern pathologists call cribriform. Dividing cells (mitotic figures) and areas of cell death (necrosis) are rarely seen. Low-grade tumors may grow into surrounding tissue but are often cured by surgery alone.
High grade — The tumor is made up of larger, more abnormal-looking (atypical) cells that contain less mucin. The cells are often joined into large sheets, a pattern pathologists call solid growth. Unlike low-grade tumors, mitotic figures and necrosis are commonly seen. High-grade tumors grow more quickly and are more likely to spread to other parts of the body.

Perineural invasion

In non-intestinal-type sinonasal adenocarcinoma, the pathologist looks for perineural invasion, which means cancer cells were seen attached to or growing along the outside of a nerve. Nerves run throughout the head and neck, carrying signals such as temperature, pressure, and pain between the body and the brain. Perineural invasion matters because cancer cells can use nerves as a pathway to travel into surrounding tissues, which raises the risk of the tumor returning after treatment. If perineural invasion is present, it will be described in your pathology report.

Lymphovascular invasion

Lymphovascular invasion means that cancer cells from the non-intestinal-type sinonasal adenocarcinoma were seen within a blood or lymphatic vessel. Blood vessels carry blood throughout the body, and lymphatic vessels carry a fluid called lymph. Both types of vessels connect to other parts of the body, so cancer cells that enter them can travel to distant sites such as lymph nodes or the lungs. If lymphovascular invasion is present, it will be included in your pathology report.

Surgical margins

A surgical margin is the edge of the tissue that the surgeon cuts through when removing the tumor. Margins are assessed after a procedure that removes the entire tumor, such as an excision or resection, and are usually not evaluated after a biopsy, which removes only part of the tumor. Because non-intestinal-type sinonasal adenocarcinoma is often removed in more than one piece, the pathologist may not be able to fully assess the margins, and the report may describe them as indeterminate.

Negative margin — No cancer cells are present at the cut edge of the tissue. This suggests the tumor was completely removed.
Close margin — Cancer cells are near the cut edge but do not reach it. The distance from the nearest cancer cells to the edge may be measured and reported, because a very close margin can be relevant to decisions about additional treatment.
Positive margin — Cancer cells are present at the cut edge. This means some tumor may remain in the body, and the treatment team will use this finding when considering whether additional surgery or radiation therapy is appropriate.

Lymph nodes

Lymph nodes are small immune organs found throughout the head and neck. Cancer cells can travel from a non-intestinal-type sinonasal adenocarcinoma through lymphatic vessels to reach these nodes, although this is uncommon, especially for low-grade tumors. Lymph nodes are not always removed at the same time as the tumor; they are usually removed only if they are enlarged or look suspicious on imaging. When lymph nodes are removed, they are examined under the microscope, and the results are described in your pathology report.

Your report will include the total number of lymph nodes examined, the number that contain cancer cells, and the size of the largest deposit of cancer cells (often called a “focus” or “deposit”). A node that contains cancer cells is described as “positive,” and a node with no cancer cells is described as “negative.” The pathologist also checks for extranodal extension, which means cancer cells have broken through the outer capsule of a lymph node and spread into the surrounding tissue. Lymph node findings are used to determine the pathologic nodal stage (pN) and, along with evidence of cancer cells spreading to other parts of the body (metastasis), may influence decisions about additional treatment, such as radiation therapy or chemotherapy.

Pathologic stage (pTNM)

The pathologic stage for non-intestinal-type sinonasal adenocarcinoma is based on the TNM staging system, as defined in the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 8th edition. This system describes the tumor using three categories: the primary tumor (pT), the regional lymph nodes (pN), and distant spread (pM). In general, a higher stage reflects more advanced disease. The metastatic stage (pM) is determined by imaging and clinical evaluation, not by the pathologist examining the surgical specimen. Because the tumor stage depends on where the cancer began, the criteria differ for tumors that start in the nasal cavity or ethmoid sinus versus those that start in the maxillary sinus.

Tumor stage (pT) — nasal cavity and ethmoid sinus

pT1 — The tumor is limited to one area (subsite) of the nasal cavity or ethmoid sinus, with or without involvement of the surrounding bone.
pT2 — The tumor involves two subsites within the nasal cavity or ethmoid sinus, or extends into an adjacent area within this region, with or without involvement of the surrounding bone.
pT3 — The tumor has invaded the floor or inner wall of the orbit (the socket that holds the eye), the maxillary sinus, the palate (the roof of the mouth), or the cribriform plate (a bony shelf at the top of the nasal cavity).
pT4a — The tumor has grown into the front part of the eye socket, the skin of the nose or cheek, a limited area at the base of the skull, the pterygoid plates (wing-shaped bones at the base of the skull), or the sphenoid or frontal sinuses.
pT4b — The tumor has grown into the deepest part of the eye socket, the coverings of the brain, the brain itself, the middle cranial fossa, specific cranial nerves, the upper throat behind the nose (nasopharynx), or a bony area at the base of the skull (clivus).

Tumor stage (pT) — maxillary sinus

pT1 — The tumor is limited to the lining (mucosa) of the maxillary sinus and has not damaged the surrounding bone.
pT2 — The tumor has eroded or destroyed bone, possibly including the hard palate or the middle nasal passage, but has not reached the back wall of the maxillary sinus or the pterygoid plates.
pT3 — The tumor has invaded the back wall of the maxillary sinus, the tissue beneath the skin, the floor or inner wall of the orbit, the pterygoid fossa (a depression at the side of the skull), or the ethmoid sinuses.
pT4a — The tumor has grown into the front part of the eye socket, the skin of the cheek, the pterygoid plates, the infratemporal fossa (a space at the side of the skull), the cribriform plate, or the sphenoid or frontal sinuses.
pT4b — The tumor has grown into the deepest part of the eye socket, the coverings of the brain, the brain itself, the middle cranial fossa, specific cranial nerves, the nasopharynx, or the clivus.

Nodal stage (pN)

pNX — The lymph nodes could not be assessed.
pN0 — No cancer cells were found in any of the lymph nodes examined.
pN1 — Cancer cells were found in a single lymph node on the same side of the neck as the tumor. The node is 3 cm or smaller and shows no extranodal extension.
pN2a — Cancer cells were found in a single lymph node on the same side of the neck that is either 3 cm or smaller with extranodal extension, or larger than 3 cm but no larger than 6 cm without extranodal extension.
pN2b — Cancer cells were found in more than one lymph node on the same side of the neck. None is larger than 6 cm, and none shows extranodal extension.
pN2c — Cancer cells were found in lymph nodes on both sides of the neck, or on the opposite side from the tumor. None is larger than 6 cm, and none shows extranodal extension.
pN3a — A lymph node containing cancer cells is larger than 6 cm and shows no extranodal extension.
pN3b — A lymph node with extranodal extension is present, or multiple involved nodes show extranodal extension.

What is the prognosis?

Prognosis refers to the likely long-term outcome after a diagnosis. For non-intestinal-type sinonasal adenocarcinoma, the outlook depends heavily on the grade of the tumor, along with its size, location, and how far it has spread.

Low-grade tumors — These have a favorable outlook. They very rarely spread to lymph nodes or other parts of the body and are often cured by surgery alone.
High-grade tumors — These grow more quickly and are more likely to spread, though the overall risk of spread is still relatively low compared with some other head and neck cancers. Outcomes are less favorable than for low-grade tumors.

Other findings on the pathology report also affect the risk of the tumor returning after treatment. Positive or close surgical margins, perineural invasion, lymphovascular invasion, and cancer in the lymph nodes are each associated with a higher chance of recurrence.

What happens after the diagnosis?

Treatment for non-intestinal-type sinonasal adenocarcinoma is planned by a multidisciplinary team that may include ear, nose, and throat (ENT) surgeons, neurosurgeons for tumors near the skull base, radiation oncologists, and medical oncologists. The approach is guided by the grade, location, size, and stage of the tumor, as well as the specific findings in the pathology report.

Surgery is the main treatment, with the goal of completely removing the tumor with clear margins. For low-grade tumors, surgery alone is often enough. For high-grade tumors, or when the report shows positive or close margins, perineural invasion, lymphovascular invasion, or cancer in the lymph nodes, radiation therapy after surgery may be considered, and these specific findings directly inform that decision. Chemotherapy may be added for advanced or high-grade disease. After treatment, regular follow-up with imaging and physical examination is used to watch for any sign of the cancer returning.

Questions to ask your doctor

Where exactly did my cancer start — the nasal cavity, ethmoid sinus, or maxillary sinus?
Was my tumor low grade or high grade, and what does that mean for my outlook?
What is my pathologic stage (pT and pN), and what does that mean for my treatment?
Were the surgical margins negative, or were they indeterminate because the tumor was removed in pieces?
Was perineural invasion present in my tumor?
Was lymphovascular invasion present in my tumor?
Were lymph nodes examined, and did any contain cancer cells? Was extranodal extension present?
Will I need radiation therapy or chemotherapy after surgery, and which findings in my report influenced that recommendation?
What signs of recurrence should I watch for, and how will I be monitored after treatment?
Are there any clinical trials available for my type of cancer?