Basal Cell Adenocarcinoma of the Salivary Glands: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
May 8, 2026

Basal cell adenocarcinoma is a rare type of cancer that starts in the salivary glands — the glands that make saliva. It is called “basal cell” because the tumor cells resemble the basal cells normally found at the base of salivary gland ducts. Most basal cell adenocarcinomas are low grade and grow slowly. They are still considered cancer because the tumor cells can invade nearby tissues and, in a small number of cases, spread (metastasize) to other parts of the body. Most patients are cured by surgery alone.

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 basal cell adenocarcinoma?

The cause of basal cell adenocarcinoma is not known in most cases. It is not strongly linked to smoking, alcohol, or any other lifestyle factor. About one in four basal cell adenocarcinomas develop within a long-standing benign tumor called a basal cell adenoma — the noncancerous counterpart of basal cell adenocarcinoma. The other three-quarters develop on their own.

A small number of patients with basal cell adenocarcinoma — particularly the type called the membranous variant (described later in the diagnosis section) — have an inherited condition called familial cylindromatosis, also known as Brooke-Spiegler syndrome. This condition is caused by mutations in the CYLD gene. People with this syndrome develop multiple skin tumors called cylindromas (often on the scalp), as well as other types of glandular and skin tumors. If your pathology report describes the membranous variant of basal cell adenocarcinoma, or if you have a personal or family history of multiple skin tumors of this kind, your doctor may recommend referral to a medical geneticist or genetic counselor to discuss testing. Most basal cell adenocarcinomas, however, are not part of any inherited syndrome. The genetic changes in tumor cells occur by chance during a person’s lifetime and cannot be passed to children.

Where does basal cell adenocarcinoma start?

About 90% of basal cell adenocarcinomas start in the parotid gland — the largest salivary gland, which sits in front of and below each ear. The remainder occur in the submandibular gland (under the jaw), the sublingual gland (under the tongue), or in the small minor salivary glands distributed throughout the lining of the mouth and throat. Most basal cell adenocarcinomas are smaller than 3 cm at the time of diagnosis.

Basal cell adenocarcinoma can occur at any age but is most common between 60 and 80 years old. It affects men and women in roughly equal numbers.

What are the symptoms of basal cell adenocarcinoma?

Most basal cell adenocarcinomas grow slowly and produce only mild symptoms in the early stages:

Painless lump or swelling — A slow-growing, painless mass in the salivary gland is the most common finding. In the parotid gland, the lump is felt under the skin in front of or below the ear.
Pain or tenderness — Uncommon at first. New pain can be a warning sign that the tumor has invaded a nerve or has undergone high-grade transformation.
Numbness or facial weakness — The facial nerve runs through the parotid gland. Tumors that press on or invade this nerve can cause numbness, tingling, or weakness of part of the face. This is uncommon and, when present, suggests a more aggressive tumor.
Sudden change in a long-standing lump — A lump that has been stable for years and then suddenly starts to grow more quickly may suggest that a previous benign basal cell adenoma has turned into basal cell adenocarcinoma.
Multiple skin tumors on the scalp or face — A clue that the patient may have familial cylindromatosis (Brooke-Spiegler syndrome), particularly in patients with the membranous variant.

How is the diagnosis made?

The diagnosis is made after a tissue sample is examined under the microscope by a pathologist. Most patients first have an imaging test — usually an ultrasound, CT scan, or MRI — that shows a mass in the salivary gland. A fine needle aspiration biopsy (FNAB) is often done first to take a small sample of cells through a thin needle. If the FNAB does not give a clear answer, a core needle biopsy may be done instead. In many cases, the entire tumor is removed in a single operation, and the diagnosis is made on this larger sample.

Under the microscope, the pathologist looks for a tumor made up of dark-staining basaloid cells arranged in nests. The cells at the edge of each nest line up side-by-side in a regimented row — a pattern called peripheral palisading. Inside each nest, there may be lighter-staining cells and small duct-like structures. A thick pink layer of basement membrane-like material often surrounds the tumor nests. The cells themselves have round or oval nuclei (the part of the cell that holds DNA), often with an open or empty appearance. The tumor cells can be arranged in several patterns within the same tumor:

Solid pattern — Cells form sheets or large nests. The most common pattern.
Trabecular pattern — Cells form long, thin cords or strands.
Tubular pattern — Cells form small, round, duct-like structures.
Membranous pattern — Tumor nests are surrounded by thick, prominent layers of basement membrane material. This is the variant most often associated with familial cylindromatosis (Brooke-Spiegler syndrome) and the variant most likely to be linked to a CYLD gene mutation.

The most important feature that distinguishes basal cell adenocarcinoma from its benign counterpart, basal cell adenoma, is invasion. Basal cell adenocarcinoma invades surrounding salivary tissue, fat, blood vessels, or nerves; basal cell adenoma does not. The other key tumor that basal cell adenocarcinoma must be told apart from is adenoid cystic carcinoma, which can also show basaloid cells and similar architectural patterns. The two are distinguished by their staining pattern under additional testing and, when needed, by molecular testing.

To confirm the diagnosis, the pathologist often uses immunohistochemistry, a staining technique that highlights specific proteins in tumor cells. Basal cell adenocarcinoma is typically positive for proteins called cytokeratin 5/6, p63, p40, S100, and SOX10. The staining pattern helps distinguish basal cell adenocarcinoma from adenoid cystic carcinoma and other tumors with a similar appearance. In some cases, particularly when familial cylindromatosis is suspected, additional molecular testing for changes in the CYLD gene may be ordered. Once the diagnosis is confirmed, additional imaging is used to assess spread before treatment is planned.

High-grade transformation

High-grade transformation means that part of the tumor has changed into a much more aggressive form of cancer. In areas of high-grade transformation, the tumor cells lose the typical features of basal cell adenocarcinoma. They become very abnormal looking (atypical and pleomorphic), divide rapidly (with many mitotic figures), and often show areas of necrosis (cell death). High-grade transformation is uncommon in basal cell adenocarcinoma, but when present, the tumor is much more likely to spread to lymph nodes and to distant sites. Treatment is usually stronger when this finding is reported, often including a neck dissection (removal of lymph nodes from the neck) and radiation therapy after surgery.

Tumor extension (extraparenchymal extension)

Extraparenchymal extension means the tumor has spread beyond the salivary gland into surrounding tissues, such as fat, muscle, or skin. This finding is reported only for tumors that arise in one of the three major salivary glands — the parotid, submandibular, or sublingual gland. Tumors with extraparenchymal extension are given a higher pathologic stage (pT) and are at higher risk of coming back after surgery.

Lymphovascular invasion

Lymphovascular invasion means that tumor cells have entered small blood vessels or lymphatic vessels in or near the tumor. These vessels can carry the cells to lymph nodes or to distant parts of the body. Lymphovascular invasion is uncommon in classic basal cell adenocarcinoma. When found, it raises the risk that the cancer will come back, and it may influence the decision to recommend radiation therapy after surgery.

Perineural invasion

Perineural invasion means that tumor cells are growing around or along a nerve. The facial nerve, which controls the muscles of facial expression, runs through the parotid gland and is the most common nerve involved when basal cell adenocarcinoma starts there. Perineural invasion can cause new pain, numbness, or facial weakness. When seen on a pathology report, it raises the risk that the tumor will come back near the original site, and your doctor may recommend radiation therapy after surgery to lower that risk.

Surgical margins

A margin is the edge of the tissue that the surgeon cuts when removing the tumor. The pathologist examines these edges under the microscope to see whether any tumor cells reach the cut surface.

Negative margin — No tumor cells are seen at the cut edge. This suggests the tumor was completely removed and the chance of it growing back is much lower.
Close margin — Tumor cells are very close to the cut edge but do not reach it. The pathologist may report the exact distance in millimeters. A close margin can raise the risk that the tumor will come back near the original site.
Positive margin — Tumor cells are seen at the cut edge of the tissue. This means tumor cells were almost certainly left behind. A positive margin usually leads to a recommendation for either more surgery or radiation therapy after surgery.

Margin assessment is especially difficult in parotid surgery because the surgeon must work around the facial nerve. For this reason, close margins are common even when the surgery has been carefully performed.

Lymph nodes

Lymph nodes are small immune organs scattered throughout the body. The lymph nodes most likely to be involved by basal cell adenocarcinoma are those in the neck. Spread to lymph nodes is uncommon in classic basal cell adenocarcinoma — about 10% of patients overall — but is more frequent when high-grade transformation is present. During surgery, lymph nodes near the tumor may be removed and sent to the laboratory in a procedure called a neck dissection. This is more often done when the tumor shows worrying features, when imaging suggests lymph node involvement, or when high-grade transformation is present.

Negative lymph node — No tumor cells are found in the node.
Positive lymph node — Tumor cells are found inside the node. The report will describe how many nodes contain tumor, the size of the largest deposit, and whether the tumor has grown beyond the outer wall of the node — a feature called extranodal extension.

Pathologic stage (pTNM)

Pathologic staging describes the size of the tumor and how far it has spread, based on the findings at surgery. It uses the TNM system: T stands for the size and extent of the primary tumor, N stands for involvement of nearby lymph nodes, and M stands for spread to distant parts of the body. Staging applies only to basal cell adenocarcinomas of the major salivary glands. Tumors of the minor salivary glands are staged using the system for the area where they started (such as the oral cavity or oropharynx).

Tumor stage (pT)

T1 — The tumor is 2 cm or smaller and confined to the salivary gland.
T2 — The tumor is larger than 2 cm but not larger than 4 cm and is still confined to the salivary gland.
T3 — The tumor is larger than 4 cm, or has spread beyond the salivary gland into surrounding soft tissue (extraparenchymal extension).
T4a — The tumor has invaded skin, the jawbone, the ear canal, or the facial nerve.
T4b — The tumor has invaded the base of the skull, nearby bones, or major blood vessels.

Nodal stage (pN)

N0 — No tumor cells in any examined lymph nodes.
N1 — A single lymph node on the same side of the neck contains tumor, and is 3 cm or smaller, with no extranodal extension.
N2a — A single lymph node on the same side of the neck is between 3 and 6 cm, or any lymph node shows extranodal extension.
N2b — Multiple lymph nodes on the same side of the neck contain tumor, none larger than 6 cm, with no extranodal extension.
N2c — Lymph nodes on both sides of the neck or on the opposite side from the tumor contain tumor, none larger than 6 cm, with no extranodal extension.
N3a — A lymph node larger than 6 cm contains tumor.
N3b — Any positive lymph node shows extranodal extension (apart from the single small node category covered under N2a).

What is the prognosis?

The outlook for most patients with basal cell adenocarcinoma is good. The tumor is generally slow-growing and is one of the more favorable salivary gland cancers. The 5-year disease-specific survival rate (the chance of being alive and free of this cancer 5 years after diagnosis) is greater than 85%. The main long-term concern is local recurrence — the tumor coming back in the same area after surgery — which has been reported in about 25–30% of patients, sometimes years later. Spread to lymph nodes occurs in about 10% of patients overall, and spread to distant sites, such as the lungs, is uncommon (around 10–15% lifetime).

Several features in the pathology report can identify patients at higher risk of a worse outcome:

High-grade transformation — The single most important warning sign. Survival drops substantially when this is present.
Tumor size larger than 4 cm — Larger tumors are more likely to come back or spread.
Extraparenchymal extension — Tumors that have grown beyond the salivary gland are at higher risk of coming back.
Positive surgical margins — Incompletely removed tumors are more likely to come back.
Perineural and lymphovascular invasion — Both are linked with a higher risk of the tumor coming back.
Lymph node involvement — Spread to lymph nodes raises the risk of distant spread.

What happens after the diagnosis?

Treatment for basal cell adenocarcinoma is led by a head and neck surgeon. The surgeon often works with a radiation oncologist, and (for syndromic cases) with a medical geneticist and dermatologist. The main treatment is surgery to remove the entire tumor.

Parotidectomy — Removal of part or all of the parotid gland. Most basal cell adenocarcinomas of the parotid gland are treated with a superficial parotidectomy or, for deeper tumors, a total parotidectomy. The facial nerve is preserved whenever possible. Submandibular and sublingual tumors are removed along with the entire affected gland.
Neck dissection — Removal of lymph nodes from one or both sides of the neck. Done when there is clinical or imaging evidence of lymph node involvement, when high-grade transformation is present, or when the tumor is very large. Neck dissection is often not needed for small, classic basal cell adenocarcinomas.
Radiation therapy after surgery — Recommended when high-grade transformation is present, when surgical margins are positive or close, when perineural or lymphovascular invasion is identified, when lymph nodes are involved, or for advanced-stage tumors. Radiation is given as a series of daily treatments over several weeks.
Standard chemotherapy — Generally not very effective in basal cell adenocarcinoma and is reserved for selected patients with advanced disease.
Genetic evaluation — Recommended for patients with the membranous variant, for patients with multiple skin tumors of the cylindroma type, and for patients with a family history suggestive of familial cylindromatosis. Confirming the diagnosis allows screening for other features and testing family members.
Long-term surveillance — Regular clinical examination of the head and neck, with imaging as needed, continues for many years after treatment because of the risk of late local recurrence.

Questions to ask your doctor

Where exactly did the tumor start, and how large was it?
Did the tumor develop on its own, or did it arise within a previous basal cell adenoma?
What is the pathologic stage (pT, pN, and overall TNM stage) of my cancer?
Was high-grade transformation seen anywhere in the tumor?
Was the tumor completely removed? What were the surgical margins?
If a margin was positive or close, will I need more surgery or radiation therapy?
Were perineural or lymphovascular invasion identified?
Were any lymph nodes involved by tumor?
Was my tumor the membranous variant, and should I be tested for familial cylindromatosis (Brooke-Spiegler syndrome)?
If I have the syndrome, what other screening do I need, and what does it mean for my children?
Will I need radiation therapy after surgery?
What is my estimated risk of the cancer coming back?
What is the schedule for follow-up examinations and imaging, and how long will it continue?
Will I have any lasting facial weakness, numbness, or dry mouth from the surgery?