Mucosal Melanoma of the Nasal Cavity and Paranasal Sinuses: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
July 14, 2026

Mucosal melanoma of the nasal cavity and paranasal sinuses is a rare, fast-growing cancer that arises from melanocytes, the cells that produce pigment (melanin) in the lining of the nose and sinuses. The nasal cavity is the space behind the nose through which air passes into the lungs, and the paranasal sinuses are air-filled spaces in the bones around the nose, including the maxillary, ethmoid, frontal, and sphenoid sinuses. Melanocytes are normally present in small numbers within this lining, and when they grow uncontrollably and form a malignant tumor, the result is mucosal melanoma. Unlike cutaneous (skin) melanoma, mucosal melanoma is not caused by sun exposure. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

How common is mucosal melanoma in this location?

Mucosal melanoma of the head and neck is rare, accounting for less than 1 percent of all melanomas. About 80 percent of head and neck mucosal melanomas arise in the nasal cavity or maxillary sinus. It most commonly affects older adults and is uncommon in younger people. There is no strong evidence that it affects one sex or racial group more than another.

What causes mucosal melanoma?

The exact cause of mucosal melanoma of the nasal cavity and paranasal sinuses is not fully understood. Unlike cutaneous melanoma, it is not caused by ultraviolet radiation from the sun, and there is no proven link to tobacco, alcohol, chemical exposure, or viral infection. Some tumors arise in areas of pre-existing pigmentation in the lining (called mucosal melanosis), but many develop without any clear precursor. Mucosal melanoma has a distinct genetic profile from that of skin melanoma, as described further in the biomarker section below.

What are the symptoms?

The symptoms of mucosal melanoma of the nasal cavity and paranasal sinuses are often nonspecific and may resemble sinus infections or inflammatory conditions, which can delay the diagnosis. Common symptoms include nasal obstruction or congestion, recurrent nosebleeds, nasal discharge that may be blood-stained, and facial pressure or sinus discomfort. During an endoscopic examination, the tumor may appear as a fleshy, polyp-like mass. It may be darkly pigmented, but up to half of these tumors lack visible pigment and appear pink or gray. Some people have enlarged lymph nodes at the time of diagnosis, and in some cases the cancer has already spread to distant parts of the body.

How is the diagnosis made?

The diagnosis of mucosal melanoma usually begins when a suspicious mass is found during nasal endoscopy or imaging. A biopsy of the abnormal tissue is performed, and the diagnosis is made after a pathologist examines the sample under the microscope. Under the microscope, mucosal melanoma consists of highly abnormal tumor cells that vary in shape; they may be epithelioid (large and polygonal), spindle-shaped, round, clear, plasmacytoid, or undifferentiated, and more than one cell type is often present within the same tumor. The tumor may grow in sheets, nests, or bundles of elongated cells, and invasion into the underlying connective tissue is common; advanced tumors may grow into cartilage or bone. The surface lining may show abnormal melanocytes spreading upward within it (called pagetoid spread) or arranged along the bottom layer (called lentiginous growth). Dividing cells (mitotic figures) are usually numerous and may look abnormal, and areas of necrosis (cell death) are common.

Because up to half of these tumors lack visible pigment (a form called amelanotic melanoma), additional tests are often needed to confirm the diagnosis. Immunohistochemistry, a test that uses specially labeled antibodies to detect proteins in the tumor cells, is especially important in these cases. The tumor cells usually express melanocyte-related proteins, including S100, SOX10, HMB-45, Melan-A (also called MART1), tyrosinase, and MITF. Because no single marker identifies every case, a panel of markers is used, and these stains also help distinguish mucosal melanoma from other cancers that can look similar. Imaging studies are then used to determine how far the tumor has spread. A CT scan shows bone destruction and helps with surgical planning, while an MRI provides better soft-tissue detail and is especially useful for assessing growth into the orbit (eye socket), brain, or surrounding structures. A PET-CT scan may be used to evaluate lymph nodes and detect distant spread.

Subtypes of mucosal melanoma

A subtype is a specific form of a cancer that shares the main features of the overall disease but has distinct microscopic characteristics. Identifying the subtype of a mucosal melanoma can provide additional information about how the tumor is likely to behave.

Mucosal lentiginous melanoma — Abnormal melanocytes spread in a line along the bottom layer of the surface lining. This growth pattern is common in melanoma of the nasal cavity and sinuses.
Nodular melanoma — The tumor forms a more compact, rounded mass and may show little involvement of the surface lining. It is often deeply invasive by the time it is diagnosed.
Desmoplastic mucosal melanoma — This rare subtype is made up mainly of spindle-shaped tumor cells within dense fibrous tissue. It often lacks visible pigment and can resemble other spindle cell tumors. Perineural invasion is frequently present, and extensive immunohistochemical testing is often needed to confirm the diagnosis.

Depth of invasion

Depth of invasion describes how far the mucosal melanoma has grown into the surrounding tissues. Under the microscope, the pathologist assesses how deeply the tumor extends beneath the surface lining and whether it invades cartilage, bone, or nearby structures; imaging studies such as CT and MRI help evaluate the extent of local invasion. Unlike cutaneous melanoma, where tumor thickness (Breslow depth) is used for staging, tumor thickness is not used to stage mucosal melanoma. Most mucosal melanomas of the head and neck are already advanced at diagnosis, so the overall stage depends more on local extension and on spread to lymph nodes or distant organs than on thickness.

Perineural invasion

Perineural invasion means that 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 is common in mucosal melanoma, especially the desmoplastic subtype, and it is considered a high-risk feature because it indicates that the tumor is spreading into surrounding tissue and 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 mucosal melanoma 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, the lungs, or the liver. 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 mucosal melanoma often grows into nearby structures in a confined space, complete removal with clear margins can be difficult, and the pathologist may not always be able to fully assess the margins.

Negative margin — No tumor cells are present at the cut edge of the tissue. This suggests the tumor was completely removed.
Close margin — Tumor cells are near the cut edge but do not reach it. The distance from the nearest tumor cells to the edge may be measured and reported, because a very close margin can be relevant to decisions about additional treatment.
Positive margin — Tumor 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 connected by lymphatic vessels. Cancer cells from a mucosal melanoma can spread through these vessels to reach the lymph nodes. When lymph nodes are removed, sometimes in a procedure called a neck dissection, they are examined under the microscope, and the results are described in your pathology report.

Your report will include the number of lymph nodes examined and the number that contain 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 may also check for extranodal extension, which means cancer cells have broken through the outer capsule of a lymph node into the surrounding tissue. Lymph node involvement is associated with a higher risk of the cancer spreading to other parts of the body (metastasis) and a less favorable outlook. At the time of diagnosis, about 20 percent of patients already have cancer in the lymph nodes.

Biomarker and molecular testing

Biomarkers are proteins or genetic changes in the tumor cells that can help guide treatment decisions. In mucosal melanoma of the nasal cavity and paranasal sinuses, biomarker testing is most often performed in advanced or metastatic disease to identify potential targeted therapy or immunotherapy options. Importantly, the genetic profile of mucosal melanoma differs from that of sun-related skin melanoma.

KIT

KIT is a gene that helps control cell growth and produces a protein called CD117. Mutations in the KIT gene are more common in mucosal melanoma than in skin melanoma. When a KIT mutation is found through molecular testing, treatment with a KIT-targeted drug may be considered. KIT mutations are detected using molecular genetic testing on tumor tissue, and the result is reported as either a detectable mutation or no mutation identified, sometimes with the specific mutation named. You can read more in the KIT mutations in melanoma article.

BRAF

BRAF is a gene involved in cell signaling. BRAF mutations are less common in mucosal melanoma than in cutaneous melanoma, but when a mutation such as BRAF V600E is present, targeted therapy with BRAF and MEK inhibitors may be an option. BRAF mutations are identified using molecular testing, and the report will indicate whether a mutation is present and may specify the type. You can read more in the BRAF mutations in melanoma article.

NRAS

NRAS is another gene involved in cell growth signaling, and NRAS mutations occur in a portion of mucosal melanomas. There is currently no approved targeted drug specifically for NRAS-mutant melanoma, but the result may provide prognostic information and may identify eligibility for clinical trials. NRAS mutations are detected using molecular testing on tumor tissue.

PD-L1

PD-L1 is a protein that helps cancer cells avoid detection by the immune system. Drugs called immune checkpoint inhibitors are a mainstay of treatment for advanced melanoma, and PD-L1 testing may provide additional information about the likelihood of response. PD-L1 is assessed by immunohistochemistry, and the result is usually reported as the percentage of tumor cells staining or as a score. It is worth noting that mucosal melanoma tends to respond less consistently to immunotherapy than sun-related skin melanoma. You can read more in the PD-L1 and tumor mutational burden in melanoma article, or in the full Biomarkers and Molecular Testing section.

Pathologic stage (pTNM)

Mucosal melanoma of the head and neck is staged using its own version of the TNM system, defined in the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 8th edition. This system is different from the one used for other cancers of the nasal cavity and sinuses. It describes the tumor using three categories: the primary tumor (pT), the regional lymph nodes (pN), and distant spread (pM). Because mucosal melanoma is considered advanced at the time of diagnosis, there is no pT1 or pT2, and staging begins at pT3.

Tumor stage (pT)

pT3 — The tumor is limited to the lining (mucosa) and the tissue just beneath it, regardless of its thickness or size.
pT4a — The tumor has grown into deeper soft tissue, cartilage, bone, or the overlying skin.
pT4b — The tumor has grown into the brain, the coverings of the brain (dura), the base of the skull, certain cranial nerves, the chewing muscles (masticator space), the carotid artery, the space in front of the spine, or structures in the chest.

Nodal stage (pN)

pN0 — No cancer cells were found in the regional lymph nodes.
pN1 — Cancer cells were found in one or more regional lymph nodes.

These categories are combined into an overall stage. Because mucosal melanoma starts at pT3, the earliest stage is stage III (pT3, no nodes, no distant spread). Stage IVA describes deeper local growth (pT4a) or lymph node involvement, stage IVB describes very advanced local growth (pT4b), and stage IVC describes a tumor that has spread to distant parts of the body.

What is the prognosis?

Prognosis refers to the likely long-term outcome after a diagnosis. Mucosal melanoma of the nasal cavity and paranasal sinuses is a fast-growing cancer, and the reported five-year overall survival rate ranges from approximately 20 to 50 percent. The outlook depends on several findings.

Extent of local invasion — Tumors confined to the nasal cavity tend to have better outcomes than those that involve deeper sinus structures, bone, or the orbit.
Lymph node involvement — Cancer found in the lymph nodes is associated with a higher risk of distant spread and a less favorable outlook.
Distant metastasis — Spread to distant organs is the strongest factor associated with a poor outlook.
Perineural invasion — This high-risk feature is associated with a greater chance that the tumor will return.

What happens after the diagnosis?

Treatment for mucosal melanoma of the nasal cavity and paranasal sinuses is planned by a multidisciplinary team that may include ear, nose, and throat (ENT) surgeons, neurosurgeons for tumors near the base of the skull, radiation oncologists, and medical oncologists. The approach is guided by the extent of the tumor and the specific findings in the pathology report.

Surgery to remove the tumor is the main treatment, with the goal of complete removal with clear margins. Radiation therapy may be added to improve control of the tumor in the area where it started, particularly when margins are positive or close. For advanced or metastatic disease, immunotherapy with immune checkpoint inhibitors is a mainstay, and for tumors with a KIT or BRAF mutation, targeted therapy may be considered based on those biomarker results. After treatment, close follow-up with imaging and physical examination is important, because this cancer can return or spread.

Questions to ask your doctor

Where exactly did my tumor start, and has it grown into nearby structures such as bone or the orbit?
What is my pathologic stage, and what does that mean for my treatment?
Has the tumor spread to lymph nodes or to distant organs?
Were the surgical margins negative, and does the report suggest the tumor was completely removed?
Was perineural invasion present in my tumor?
Were biomarker tests such as KIT, BRAF, NRAS, and PD-L1 performed, and what were the results?
Am I a candidate for targeted therapy or immunotherapy?
Will I need radiation therapy after surgery, and which findings 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?