NUT Carcinoma: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
July 13, 2026

NUT carcinoma is a rare, fast-growing cancer that can develop in different parts of the body, most often in the head and neck or the chest. It is named after a genetic change involving the NUTM1 gene, which normally helps control how cells grow and mature. NUT carcinoma tends to grow and spread quickly, which makes early diagnosis and treatment important. 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 NUT carcinoma?

NUT carcinoma is caused by a mutation (genetic change) that leads to uncontrolled cell growth. The change occurs when the NUTM1 gene joins with another gene, most often BRD4 or BRD3, creating a fusion gene. A fusion gene forms when two genes that are normally separate become joined, creating an abnormal combined gene. In NUT carcinoma, this fusion gene prevents cells from maturing normally and drives rapid cancer cell growth. The reason the fusion occurs is unknown, and there are no known risk factors or inherited causes.

What are the symptoms?

The symptoms of NUT carcinoma depend on where the tumor is located. In the head and neck, it may cause swelling, difficulty swallowing, voice changes, or breathing problems. In the chest, it may cause a cough, chest pain, or shortness of breath. Some people also experience weight loss, fatigue, or pain if the cancer has spread to other parts of the body. Because these symptoms can develop quickly, they often lead to imaging and a biopsy.

How is the diagnosis made?

The diagnosis of NUT carcinoma is made after a tissue sample is examined under the microscope by a pathologist. The sample is usually obtained through a biopsy. Under the microscope, NUT carcinoma consists of small- to medium-sized cancer cells that look very similar to one another. The cells have irregularly shaped nuclei (which contain the cell’s genetic material) and prominent nucleoli (small structures within the nucleus). The cells are arranged in sheets or nests, with many mitotic figures (cells caught in the act of dividing) and areas of necrosis (cell death). One distinctive feature is the sudden production of keratin, a protein normally found in skin and hair, in areas that pathologists call “abrupt keratinization.” This feature is seen in only about one-third of cases. The tumor is often surrounded by inflammatory cells, particularly neutrophils, which are a type of immune cell.

Because NUT carcinoma is rare and can resemble other cancers, additional tests are used to confirm the diagnosis. Immunohistochemistry, a test that uses specially labeled antibodies to detect proteins in the tumor cells, is central to the diagnosis. Most NUT carcinomas show strong staining for the NUT protein, which confirms the diagnosis; the staining often appears as small dots (a punctate or speckled pattern) inside the cells. The tumor cells are also usually positive for cytokeratins, confirming that the tumor is a carcinoma, and often for p63 and p40, which point to squamous differentiation. In some cases, the cells also stain for chromogranin, synaptophysin, TTF-1, or CD34, which can make the diagnosis more challenging. A test called Ki-67 is often elevated, indicating that cells are dividing rapidly. To confirm the diagnosis, genetic tests such as fluorescence in situ hybridization (FISH) or next-generation sequencing (NGS) are used to detect the NUTM1 gene fusion. Once the diagnosis is confirmed, imaging studies such as CT, MRI, or PET are used to determine where the tumor started and how far it has spread.

Histologic grade

NUT carcinoma is not assigned a histologic grade in the way some other cancers are, because it is always considered a high-grade cancer. Being high grade means the tumor tends to grow and spread quickly. Your pathology report will not include a grade number for this tumor, and this is expected. Treatment usually begins soon after the diagnosis is made.

Perineural invasion

In NUT carcinoma, the pathologist looks for perineural invasion, which means cancer cells were seen attached to or growing along the outside of a nerve. Nerves carry signals such as temperature, pressure, and pain between the body and the brain. Perineural invasion can cause pain, numbness, or weakness if important nerves are affected, and it can make the tumor harder to remove completely with surgery. If perineural invasion is present, it will be described in your pathology report.

Lymphovascular invasion

Lymphovascular invasion means that cancer cells from the NUT carcinoma were found 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 and spread (metastasize) to distant sites. If lymphovascular invasion is present, it will be included in your pathology report, and it may influence decisions about additional treatment.

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.

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 body, including the neck and chest. Cancer cells from a NUT carcinoma can travel through lymphatic vessels to reach these nodes. When lymph nodes are removed during surgery, sometimes in a procedure called a neck dissection for head and neck tumors, 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. 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, along with the finding of cancer cells spreading to other parts of the body (metastasis), may influence decisions about additional treatment.

Staging

Because NUT carcinoma can arise in different parts of the body, there is no single staging system for it, unlike many other cancers, which have a standard system. Instead, the stage is based on where the tumor started and how far it has spread, which is determined mainly by imaging studies such as CT, MRI, and PET scans. In general, a tumor that is confined to where it started has a lower stage than one that has grown into nearby structures or spread to lymph nodes or distant organs. Your treatment team will explain which staging approach applies to the location of your tumor.

What is the prognosis?

Prognosis refers to the likely long-term outcome after a diagnosis. NUT carcinoma is a fast-growing, high-grade cancer, and outcomes have generally been poor, although they vary depending on where the tumor started and the specific genetic change involved. Across all cases, the median survival (the point at which half of patients are still alive) has been reported at about 6.5 months. Two factors have the strongest influence on this outlook.

Tumor location — Tumors that start in the chest (thoracic NUT carcinoma) tend to have a less favorable outlook than tumors that start outside the chest.
Type of gene fusion — Tumors with a BRD4–NUTM1 fusion tend to behave more aggressively than those with other fusions. Thoracic tumors with a BRD4–NUTM1 fusion have had the shortest reported median survival (about 4.4 months), while tumors outside the chest with a non-BRD4 fusion have had a longer median survival (about 36.5 months).

Complete surgical removal of the tumor and early treatment with radiation therapy have been linked to better outcomes. Because NUT carcinoma is rare and research is ongoing, these figures reflect past experience, and newer targeted treatments are being studied that may change the outlook in the future.

What happens after the diagnosis?

Treatment for NUT carcinoma is planned by a multidisciplinary team that may include surgeons, radiation oncologists, and medical oncologists, with the specific specialists depending on where the tumor started. Because this tumor grows quickly, treatment usually begins soon after the diagnosis and often combines more than one approach.

When the tumor can be removed, surgery followed by radiation therapy is often used, and complete removal with clear margins is the goal. Chemotherapy is frequently given, although traditional chemotherapy has not provided long-lasting responses in most patients; some studies suggest that ifosfamide-based regimens may help a small number of patients, particularly children. Researchers are also studying newer targeted drugs called BET inhibitors, which are designed to block the abnormal protein produced by the NUTM1 fusion. Clinical trials of these and other treatments are ongoing, and your oncology team can discuss whether a trial is appropriate for you. After treatment, close follow-up with imaging and physical examination is important, because this tumor can return or spread.

Questions to ask your doctor

Where did my NUT carcinoma start, and how far has it spread?
How was the diagnosis confirmed, and which NUTM1 gene fusion was found in my tumor?
What does the location and fusion type mean for my outlook?
If surgery is possible, what will the margin results mean for my need for further treatment?
Was perineural or lymphovascular invasion present in my tumor?
Were lymph nodes examined, and did any contain cancer cells?
What combination of surgery, radiation, and chemotherapy is being recommended for me, and why?
Are there clinical trials, including trials of BET inhibitors or other targeted drugs, that I may be eligible for?
What signs of recurrence should I watch for, and how will I be monitored after treatment?
Which specialists will be involved in my care?