Your pathology report for salivary gland neoplasm of uncertain malignant potential (SUMP)

Salivary gland neoplasm of uncertain malignant potential (SUMP) is a descriptive diagnosis used by pathologists when a tumor is found in a salivary gland but there is not enough information to determine whether it is benign (noncancerous) or malignant (cancerous). It does not refer to a single disease but rather to a range of possible benign and malignant tumors that require further testing or surgical removal for a definitive diagnosis.

This term is part of the Milan System for Reporting Salivary Gland Cytopathology, which provides standardized categories for reporting results from fine needle aspiration (FNA) biopsies of salivary gland masses.

When is this diagnosis made?

The diagnosis of SUMP is usually made after a fine needle aspiration (FNA) biopsy of a lump or mass in a major salivary gland, most often the parotid gland. During an FNA, a doctor uses a thin needle to remove a small sample of cells, which is then examined under the microscope by a pathologist.

A pathologist makes this diagnosis when:

• The sample clearly contains neoplastic (tumor) cells, not inflammation or infection.

• The features are not specific enough to determine whether the tumor is benign or malignant.

• The features are not specific enough to determine exactly what type of salivary gland tumor is present.

Several factors can make it difficult to give a definitive diagnosis on FNA:

• Overlap in appearance between certain benign and malignant tumors.

• Partial sampling, where the needle collects only one area of a mixed or complex tumor.

• Cellular changes caused by inflammation, prior surgery, or cystic degeneration that mimic malignancy.

Because of these challenges, the SUMP category is used as a “cautious” or “intermediate” diagnosis to indicate that a true tumor is present, but more information—usually from a surgical excision—is needed to classify it.

What causes a salivary gland neoplasm?

SUMP itself is not a disease but a diagnostic label that applies to various salivary gland neoplasms. The exact cause of these tumors is not always known. Most develop sporadically (by chance) and are not linked to inherited genetic conditions.

Salivary gland neoplasms can occur in any of the major salivary glands (parotid, submandibular, or sublingual) or in smaller glands located throughout the mouth. Most are benign, such as pleomorphic adenoma or Warthin tumor, but some are malignant, including mucoepidermoid carcinoma and acinic cell carcinoma.

The SUMP category includes any tumor that shows features of a neoplasm but cannot yet be clearly identified as one of these specific types.

What do SUMP tumors look like under the microscope?

Under the microscope, the pathologist sees clusters of abnormal epithelial cells forming small groups, sheets, or three-dimensional structures. These cells are not inflammatory or normal salivary cells, confirming that a neoplasm is present. However, the exact type and behavior of the tumor cannot be determined.

Pathologists may describe different cytologic patterns within the SUMP category:

• Basaloid pattern: Composed of small, dark cells that can resemble both benign basal cell adenoma and malignant adenoid cystic carcinoma.

• Oncocytic pattern: Made up of larger pink cells with granular cytoplasm, seen in tumors such as oncocytoma or Warthin tumor.

• Unspecified pattern: Mixed or nonspecific features that do not match any single tumor type.

In the largest studies, the parotid gland is the most common site, and the majority of SUMP cases fall into these three microscopic groups.

What is the risk that a SUMP is cancer?

The risk of malignancy (ROM) for SUMP is approximately 30% to 35%, meaning that about one in three cases turns out to be cancer after the tumor is surgically removed and examined in full.

The risk of neoplasm (RON)—the likelihood that the sample truly represents a tumor rather than a reactive or inflammatory process—is very high, around 95%.

The risk of malignancy also varies slightly depending on the microscopic pattern:

• Basaloid type: Around 39% are malignant.

• Oncocytic type: Around 8% are malignant.

• Unspecified type: Around 41% are malignant.

The most common benign tumors found in this category are pleomorphic adenoma and oncocytoma, while the most common malignant tumor is mucoepidermoid carcinoma.

What additional tests may be performed?

To help narrow down the diagnosis, pathologists may perform immunohistochemistry or molecular tests on the FNA sample. These tests look for proteins or genetic changes that are characteristic of certain salivary gland tumors.

However, because FNA samples are small, these tests are sometimes inconclusive, and a larger tissue sample from surgery is needed for a final diagnosis.

What happens next?

If your pathology report says salivary gland neoplasm of uncertain malignant potential, your doctor will usually recommend surgical removal of the mass. Examining the entire tumor allows the pathologist to determine:

• Whether the tumor is benign or malignant.

• The exact tumor type (for example, pleomorphic adenoma or mucoepidermoid carcinoma).

• Whether the tumor has been completely removed.

In some cases, if the tumor is small and appears benign on imaging, your doctor may suggest monitoring with regular follow-up instead of immediate surgery. The best approach depends on the tumor’s size, location, and your overall health.

What is the prognosis for SUMP?

The prognosis for most people with a SUMP diagnosis is excellent. Most of these tumors are benign, and complete surgical removal is curative.

If the final diagnosis after surgery shows cancer, it is often a low-grade (slow-growing) type with a good outcome when treated early.

A SUMP diagnosis does not mean cancer, but it indicates that cancer cannot be ruled out until the tumor is fully examined.

Questions to ask your doctor

• Do I need surgery to confirm the diagnosis?

• What type of surgery is recommended?

• Were any special stains or molecular tests performed?

• What will happen if I choose to monitor the tumor instead of having surgery?

• What follow-up will I need after treatment?