Salivary gland cancer (SGC) is a rare malignancy that begins in the cells of the salivary glands, which include the large parotid, submandibular, and sublingual glands, as well as hundreds of minor glands throughout the mouth and throat. How fast this cancer grows does not have a single answer because the velocity of growth is highly dependent on the tumor’s specific biological characteristics. SGCs exhibit a wide spectrum of behaviors, ranging from very slow-growing masses that may be present for years to aggressive tumors that expand rapidly over a few months.
How Salivary Gland Cancer Subtypes Dictate Growth Speed
The most significant factor determining how fast a salivary gland cancer grows is its specific histological subtype, which is the type of cell the cancer originated from. The roughly 20 distinct subtypes of SGC are broadly categorized based on their typical growth patterns.
Slow-Growing Subtypes
Several subtypes are known for their indolent behavior, often developing slowly over many years before being diagnosed. Acinic cell carcinoma is typically a low-grade tumor with a favorable outcome. Adenoid Cystic Carcinoma is characteristically slow-growing, though it has an aggressive tendency to spread along nerves and recur many years after initial treatment. Polymorphous low-grade adenocarcinoma, which almost always starts in the minor salivary glands, is also known for its very slow growth. These tumors can often grow to a noticeable size without causing immediate distress, potentially delaying detection.
Fast-Growing Subtypes
In contrast, other subtypes exhibit a more aggressive and rapid growth pattern. Salivary duct carcinoma is recognized as a high-grade tumor that spreads quickly to nearby lymph nodes and other parts of the body. Certain adenocarcinomas, such as oncocytic carcinoma, also grow and spread more quickly than other types. Mucoepidermoid carcinoma, the most common type of SGC, can present as either slow-growing or fast-growing, depending on its specific grade.
Clinical Markers That Define Tumor Velocity
While the specific cancer subtype provides a baseline for expected growth speed, physicians use clinical markers to quantify the tumor’s velocity and potential for spread. These markers, primarily tumor grade and tumor stage, help to determine the aggressiveness of the individual malignancy.
Tumor grade is a microscopic measure that reflects how quickly the cancer cells are dividing and how abnormal they appear compared to normal cells. Low-grade tumors, often described as well-differentiated, have cells that look very much like normal salivary gland cells and tend to grow slowly. Conversely, high-grade tumors are poorly-differentiated, meaning their cells look significantly different from normal cells, which is a strong indicator of rapid growth and a greater likelihood of spreading. Intermediate-grade tumors fall between these two extremes in both appearance and expected growth rate.
Tumor stage describes the extent of the cancer in the body, relating to the tumor’s size and whether it has spread to lymph nodes or distant sites. Rapidly growing tumors can quickly progress to a higher stage by achieving a larger size or by invading surrounding soft tissue and lymph nodes. For instance, a tumor larger than 4 centimeters or one that has spread to a neck lymph node is classified as Stage III or higher. Local invasion, where the cancer grows into nearby structures like bone or nerves, is a sign of aggressive behavior.
The Patient Experience: Symptoms and Detection Timelines
The rate at which a salivary gland cancer grows directly influences the timeline and presentation of symptoms a patient experiences. The difference in growth speed often dictates whether a tumor is detected early or only after it has become large or caused functional problems.
A slow-growing tumor often presents as a painless lump or swelling in the area of the ear, cheek, or jaw that may have been present for many months or even years. Because these masses are typically not painful and expand gradually, patients may delay seeking medical attention until the tumor is quite large.
In contrast, a rapidly growing tumor typically leads to a quicker onset of noticeable, and often more severe, symptoms. Patients may observe rapid swelling, persistent pain in the face or neck, or the sudden development of facial nerve weakness or numbness. This rapid change in symptoms often prompts earlier consultation with a physician, even if the tumor is small. Masses in the parotid gland may be more easily felt on the cheek or near the ear, while those in the minor glands inside the mouth might be found during a routine dental exam.
Tracking and Responding to Tumor Growth
Once a salivary gland mass is identified, medical professionals use specific methods to assess its growth velocity and inform the management strategy. Determining the rate of expansion is a procedural step that influences the urgency and type of treatment.
Imaging techniques like Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans are used to measure the tumor’s size and monitor its growth over time. These scans provide detailed pictures of the internal structure, which is crucial for tracking any increase in volume or spread to adjacent soft tissue, lymph nodes, or distant organs. A biopsy, such as a fine needle aspiration, is performed to obtain a tissue sample, which is then examined by a pathologist to confirm the cancer subtype and assign a tumor grade, providing the definitive measure of cellular aggressiveness.
The assessed velocity of the tumor dictates the management strategy. Slow-growing, low-grade tumors may sometimes allow for a less urgent treatment approach, although surgery remains the primary treatment for most malignant SGCs. For fast-growing, high-grade tumors, immediate and aggressive intervention is necessary, typically involving surgery to remove the tumor and surrounding lymph nodes, followed by adjuvant treatments like radiation therapy or chemotherapy. Targeted therapy or clinical trials may also be considered for high-grade tumors based on specific genetic markers that drive the rapid growth.