Parotid Tumours vs. Other Salivary Gland Tumours: What’s the Difference?
The Salivary Glands: for Digestion, Lubrication and Oral Health
Salivary glands play a crucial role in our day-to-day lives, often without us realising it. These glands produce saliva, a vital fluid that aids digestion, protects teeth from decay, and keeps the mouth moist, enabling us to speak, swallow, and taste comfortably. The major salivary glands — parotid, submandibular, and sublingual — are located around the face and jaw, while hundreds of minor salivary glands are scattered across the lips, cheeks, and throat.
Like any part of the body, salivary glands can develop problems, with tumours being one of the most significant concerns. While salivary gland tumours are relatively rare, they are a cause for attention as they can range from benign (non-cancerous) to malignant (cancerous) [1]. Among these, parotid gland tumours are the most common, but tumours can also occur in the submandibular, sublingual, or minor salivary glands.
Understanding the differences between parotid tumours and those in other salivary glands is vital for early recognition, diagnosis, and treatment. This blog will explore the distinctions, shedding light on their prevalence, symptoms, and management, so you can gain clarity on this often-overlooked area of health. Whether you are seeking knowledge for yourself or a loved one, knowing these differences can make all the difference in addressing salivary gland tumours effectively.
What Are the Different Types of Salivary Glands?
The salivary glands are a network of glands responsible for producing and secreting saliva, a fluid essential for digestion, oral hygiene, and overall mouth comfort. These glands are categorised into major salivary glands and minor salivary glands, each playing a specific role in saliva production.
1. Parotid Glands
The parotid glands are the largest of the salivary glands and are located on either side of the face, just in front of and below the ears [2]. Each parotid gland secretes saliva into the mouth through the parotid duct (Stensen’s duct), which opens near the upper second molar. Parotid glands primarily produce a watery, enzyme-rich saliva that aids in breaking down food during digestion. Given their size and location, parotid glands are the most common site for salivary gland tumours.
2. Submandibular Glands
Positioned beneath the lower jaw, or mandible, the submandibular glands are the second-largest salivary glands [3]. They produce a mix of watery and mucous saliva, contributing to both lubrication and digestion. Saliva from the submandibular glands is transported into the mouth through the submandibular duct (Wharton’s duct), which opens into the floor of the mouth. Tumours in these glands are less frequent than in the parotid but tend to have a higher likelihood of malignancy.
3. Sublingual Glands
The smallest of the major salivary glands, the sublingual glands are located beneath the tongue, in the floor of the mouth. Unlike the parotid and submandibular glands, these glands produce saliva that is primarily mucous in consistency. Saliva from the sublingual glands is secreted through several small ducts (Rivinus ducts) that open directly into the mouth. Tumours in the sublingual glands are rare but often more likely to be cancerous.
4. Minor Salivary Glands
In addition to the major salivary glands, there are numerous minor salivary glands—between 600 to 1,000 — spread throughout the oral cavity and throat [4]. These small glands are located in the lips, cheeks, palate, and the lining of the throat (pharynx). Unlike the major salivary glands, minor glands do not have a single large duct but release saliva directly into the oral cavity through tiny openings. Though minor salivary gland tumours are uncommon, they are more likely to be malignant when they do occur.
Each type of gland has its unique structure and function, but all are integral to maintaining oral and digestive health.
How Common Are Tumours in Salivary Glands, and Which Glands Are Most Affected?
Salivary gland tumours are uncommon, but their prevalence and malignancy rates differ based on the specific gland affected. The parotid gland is the most frequent site for these tumours, with a high percentage being benign.
Conversely, smaller glands such as the sublingual and minor salivary glands carry a significantly higher risk of malignancy. Understanding the distribution and nature of these tumours is key to early detection and effective management. The following table summarises the prevalence and malignancy rates across the different salivary glands [5]:
| Salivary Gland | Percentage of Tumours | Commonality | Benign Tumours (%) | Malignant Tumours (%) |
| Parotid Gland | 80% | Most common | 75-80% | 20-25% |
| Submandibular Gland | 10-15% | Less common | 50-60% | 40-50% |
| Sublingual Gland | <1% | Very rare | 10-30% | 70-90% |
| Minor Salivary Glands | 10-15% | Scattered in the oral cavity | 25-50% | 50-75% |
Early detection and medical evaluation are especially critical when tumours arise in smaller glands, as the risk of malignancy is higher.
What Are the Most Common Types of Parotid Tumours?
The parotid glands are the largest salivary glands and the most common site for salivary gland tumours, accounting for around 80% of cases. While most parotid gland tumours are benign, a small percentage can be malignant. Understanding the types of tumours that occur in the parotid glands helps clarify their nature, symptoms, and treatment approaches.
Common Benign Parotid Tumours
Pleomorphic Adenoma
- Pleomorphic adenoma, also known as a benign mixed tumour, is the most common type of parotid gland tumour [6].
- It grows slowly, is usually painless, and feels firm or rubbery upon examination.
- Though benign, it can become large if left untreated and carries a small risk of malignant transformation over time. Surgical removal is the standard treatment.
Warthin’s Tumour
- Warthin’s tumour, or papillary cystadenoma lymphomatosum, is the second most common benign parotid tumour [7].
- It is more frequently observed in middle-aged or older individuals and has a strong association with smoking.
- Warthin’s tumours are typically painless and may occur bilaterally (on both sides) in about 7% to 10% of cases [8]. Surgical excision is usually sufficient for treatment.
Common Malignant Parotid Tumours
Mucoepidermoid Carcinoma
- Mucoepidermoid carcinoma is the most common malignant tumour in the parotid gland [9].
- It can range from low-grade (slow-growing, less aggressive) to high-grade (fast-growing, invasive) forms.
- Symptoms may include a growing mass, pain, and sometimes facial nerve weakness if the tumour affects surrounding structures. Treatment often involves surgery, sometimes followed by radiation therapy.
Acinic Cell Carcinoma
- Acinic cell carcinoma is another type of malignant tumour that primarily affects the parotid gland [10].
- It tends to grow slowly and may initially appear similar to a benign tumour.
- Although less aggressive than other malignant tumours, it can recur after removal, particularly if not completely excised [11]. Surgery is the primary treatment, with close follow-up to monitor for recurrence.
The parotid gland’s anatomical location near the facial nerve makes surgical management of these tumours complex. For both benign and malignant tumours, accurate diagnosis through imaging and biopsy is crucial to determine the best course of action. Understanding the differences between tumour types can help ensure timely and appropriate treatment, improving patient outcomes.
How are Parotid Tumours and Other Salivary Gland Tumours different?
| Factor | Parotid Tumours | Other Salivary Gland Tumours |
| Location and Anatomy | It is the largest salivary gland, and can be found near the jaw and ear. | Submandibular: under the jawSublingual: under the tongueMinor glands: scattered around the mouth and throat |
| Prevalence and Malignancy rates | Most are benign | Higher malignancy rates |
| Symptoms | Painless swelling | Pain, difficulty swallowing, speech changes in its later stages |
| Treatment | Surgery, radiation or chemotherapy in some cases | Surgery, radiation or chemotherapy in some cases |
What Types of Tumours Occur in Submandibular, Sublingual, and Minor Salivary Glands?
While parotid gland tumours are the most common, tumours in the submandibular, sublingual, and minor salivary glands are less frequent but carry a higher risk of malignancy. These glands are smaller and more anatomically dispersed, which often contributes to the aggressive nature of the tumours found in these locations.
Submandibular Gland Tumours
- The submandibular glands, located beneath the lower jaw, account for approximately 10-15% of all salivary gland tumours [12].
- Compared to the parotid glands, tumours in the submandibular glands have a higher likelihood of malignancy, with up to 40-50% being cancerous.
- Common benign tumours include pleomorphic adenoma, similar to those found in the parotid glands. However, malignant tumours are more frequently observed and include:
- Adenoid Cystic Carcinoma: A slow-growing but aggressive cancer that tends to invade nerves and nearby tissues, often recurring even after treatment [13].
- Mucoepidermoid Carcinoma: Can range from low-grade (less aggressive) to high-grade (more invasive) [14].
Sublingual Gland Tumours
- The sublingual glands, located beneath the tongue, are the smallest of the major salivary glands. Tumours here are extremely rare, representing less than 1% of all salivary gland tumours [15].
- Despite their rarity, sublingual gland tumours have a very high malignancy rate—up to 70-90% are cancerous [16].
- Malignant tumours typically include:
- Adenoid Cystic Carcinoma: Known for its slow progression but persistent recurrence and nerve invasion.
- Mucoepidermoid Carcinoma: Although less common here, it remains a serious malignancy requiring prompt treatment.
Minor Salivary Gland Tumours
- Minor salivary glands are scattered throughout the oral cavity, including the lips, cheeks, palate, throat, and even the nasal passages. Tumours in these glands make up approximately 10-15% of all salivary gland tumours [17].
- Like sublingual gland tumours, those in the minor salivary glands have a higher likelihood of malignancy, with about 50-75% being cancerous [18].
- Common tumour types include:
- Adenoid Cystic Carcinoma: The most frequent malignant tumour in minor salivary glands, characterised by nerve involvement and slow but relentless growth [19].
- Polymorphous Low-Grade Adenocarcinoma: A slow-growing malignancy typically found on the palate, with an excellent prognosis when detected early [20].
- Mucoepidermoid Carcinoma: Also observed in the minor glands, varying in severity depending on tumour grade [21].
Tumours in the submandibular, sublingual, and minor salivary glands often present later than parotid tumours, as they can be harder to detect early due to their location and smaller size. This late detection, combined with a higher risk of malignancy, makes early diagnosis and treatment critical.
What Are the Symptoms of Salivary Gland Tumours?
Salivary gland tumours can present with various symptoms, depending on the gland involved and whether the tumour is benign or malignant. Below are the most common symptoms to watch for:
- Lump or swelling near the jawline, in front of the ear, beneath the jaw, or inside the mouth.
- Facial numbness or weakness, particularly when the tumour presses on or invades the facial nerve.
- Pain or discomfort that may worsen over time, especially with rapidly growing tumours.
- Difficulty swallowing or speaking, often seen with tumours in the submandibular, sublingual, or minor salivary glands.
- Dry mouth or reduced saliva flow, leading to altered taste or difficulty chewing.
These symptoms can vary depending on the location of the tumour, but any persistent lump, pain, or functional issue should be assessed by a medical professional for proper diagnosis and treatment.
How Are Salivary Gland Tumours Diagnosed?
Diagnosing salivary gland tumours involves a combination of clinical evaluation, imaging studies, and tissue sampling to determine the tumour's nature. A thorough diagnostic approach is essential to differentiate between benign and malignant tumours and to plan appropriate treatment.
Physical Examination and Medical History
The diagnostic process begins with a detailed physical examination and discussion of the patient’s medical history. During the examination, the doctor:
- Feels for lumps or swelling near the jaw, under the chin, or inside the mouth.
- Checks for tenderness, firmness, or irregularities in the lump.
- Assesses for any signs of facial weakness, asymmetry, or numbness, which may indicate nerve involvement.
A review of symptoms such as pain, swallowing difficulties, or saliva changes, along with factors like smoking history or prior radiation exposure, helps guide further evaluation.
Imaging Studies
Imaging techniques are essential to determine the size, location, and extent of the tumour, as well as its impact on nearby structures. The most common imaging methods include:
Magnetic Resonance Imaging (MRI):
- Provides detailed images of soft tissues, making it ideal for assessing salivary gland tumours.
- Helps distinguish between benign and malignant tumours based on size, margins, and tissue characteristics.
Computed Tomography (CT) Scans:
- Offers cross-sectional images to evaluate the tumour’s size, location, and involvement of adjacent bones or tissues.
- Useful for detecting any signs of tumour spread to lymph nodes or other areas.
In some cases, an ultrasound may also be used as a non-invasive method to assess the lump and guide biopsy procedures.
Fine-Needle Aspiration Biopsy (FNAB)
A fine-needle aspiration biopsy is the gold standard for determining the nature of a salivary gland tumour. This minimally invasive procedure involves:
- Using a thin, hollow needle to extract a small tissue or cell sample from the tumour.
- Sending the sample to a laboratory for cytological analysis to identify whether the tumour is benign or malignant.
FNAB is generally safe, quick, and well-tolerated by patients. It provides valuable information that aids in diagnosis and helps guide treatment decisions, such as whether surgical removal is necessary.
By combining physical examination, imaging techniques, and fine-needle aspiration biopsy, healthcare professionals can accurately diagnose salivary gland tumours. Early and precise diagnosis is key to ensuring effective treatment and improving patient outcomes.
What Are the Treatment Options for Salivary Gland Tumours?
The treatment of salivary gland tumours primarily depends on whether the tumour is benign or malignant, its location, and its stage. Surgical removal remains the cornerstone of treatment, but additional therapies may be required for malignant cases to ensure optimal outcomes.
Surgical Removal
Surgery is the primary treatment for both benign and malignant salivary gland tumours.
- For benign tumours, surgery typically involves removing the tumour while preserving as much of the surrounding healthy tissue as possible.
- For malignant tumours, the goal is to remove the tumour entirely, sometimes along with affected lymph nodes to prevent further spread.
In parotid gland tumours, special care is taken due to the facial nerve running through the gland. Surgeons aim to preserve the nerve’s function while ensuring complete tumour excision. In some cases, nerve grafting or reconstructive procedures may be required if the tumour has invaded the nerve.
Radiation Therapy
Radiation therapy is often used as an additional treatment for malignant tumours, especially if:
- The tumour cannot be completely removed surgically.
- Cancer has spread to surrounding tissues or lymph nodes.
- It works by using high-energy rays to destroy residual cancer cells, reducing the risk of recurrence.
Chemotherapy
- Chemotherapy may be considered in advanced or metastatic salivary gland cancers where the tumour has spread beyond its original site.
- While not always the first-line treatment, it can be used alongside radiation therapy to improve outcomes in aggressive cases.
Prognosis and Outcomes
The prognosis for salivary gland tumours varies based on the tumour type, stage, and how early it is detected:
Benign Tumours:
- Generally, the prognosis is excellent after complete surgical removal.
- Recurrence is rare but may occur if the tumour is not entirely excised.
Malignant Tumours:
Several factors influence the prognosis, including:
- Tumour Grade and Stage: Low-grade tumours tend to grow slowly and have a better prognosis, while high-grade tumours are more aggressive and carry higher risks of recurrence and spread.
- Early Detection and Treatment: Early diagnosis significantly improves outcomes, as malignant tumours are more treatable when localised.
For parotid gland malignancies, the proximity to the facial nerve may complicate surgery and affect outcomes. However, advancements in surgical techniques and post-operative therapies continue to improve survival rates and quality of life.
In summary, early intervention, accurate diagnosis, and a tailored treatment approach are crucial for managing salivary gland tumours effectively. Benign tumours often have excellent outcomes, while malignant tumours require a combination of surgery, radiation, and sometimes chemotherapy to achieve the best results.
Key Takeaways: Understanding Parotid Tumours vs. Other Salivary Gland Tumours
Salivary gland tumours, though uncommon, vary significantly based on where they arise. Parotid tumours are the most frequent, with a majority being benign, while those in the submandibular, sublingual, and minor salivary glands carry a much higher risk of malignancy despite their rarity. Symptoms like lumps, facial weakness, pain, or difficulty swallowing can point to these tumours, and their presentation often depends on the gland involved.
The key takeaway is simple but vital: early detection saves lives. A small, painless swelling today could indicate something that requires prompt attention tomorrow. Ignoring these signs, however minor they may seem, can lead to unnecessary complications.
If you notice any unusual lumps, changes in facial sensation, or discomfort around the jaw, neck, or mouth, do not wait. Consult a healthcare professional who can guide you through the right diagnostic steps and treatment options.
When it comes to your health, being proactive is the greatest decision you can make. Early intervention often means better outcomes, quicker recovery, and peace of mind — because your health is too important to leave to chance.
References
- Salivary gland tumors—Ear, nose, and throat disorders. (n.d.). MSD Manual Professional Edition. Retrieved December 18, 2024, from https://www.msdmanuals.com/professional/ear-nose-and-throat-disorders/tumors-of-the-head-and-neck/salivary-gland-tumors
- Parotid gland: Anatomy, function, location & definition. (n.d.). Cleveland Clinic. Retrieved December 18, 2024, from https://my.clevelandclinic.org/health/body/23232-parotid-gland
- Ghannam, M. G., & Singh, P. (2024). Anatomy, head and neck, salivary glands. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK538325/
- De Paula, F., Teshima, T. H. N., Hsieh, R., Souza, M. M., Nico, M. M. S., & Lourenco, S. V. (2017). Overview of human salivary glands: Highlights of morphology and developing processes. The Anatomical Record, 300(7), 1180–1188. https://doi.org/10.1002/ar.23569
- Bussu, F., Parrilla, C., Rizzo, D., Almadori, G., Paludetti, G., & Galli, J. (2011). Clinical approach and treatment of benign and malignant parotid masses, personal experience. Acta Otorhinolaryngologica Italica: Organo Ufficiale Della Societa Italiana Di Otorinolaringologia E Chirurgia Cervico-Facciale, 31(3), 135–143.
- Tille, J.-C., Reychler, H., Hamoir, M., Schmitz, S., & Weynand, B. (2011). Schwannoma-like pleomorphic adenoma of the parotid. Rare Tumors, 3(4), e40. https://doi.org/10.4081/rt.2011.e40
- A R, R., Rehani, S., Bishen, K. A., & Sagari, S. (2014). Warthin’s tumour: A case report and review on pathogenesis and its histological subtypes. Journal of Clinical and Diagnostic Research : JCDR, 8(9), ZD37–ZD40. https://doi.org/10.7860/JCDR/2014/8503.4908
- Nascimento, L. A., Ferreira, J. A. S., Pio, R. B., Takano, G. H. S., & Miziara, H. L. (2014). Synchronous bilateral warthin tumors: A case report. International Archives of Otorhinolaryngology, 18(2), 217–220. https://doi.org/10.1055/s-0033-1351676
- Devaraju, R., Gantala, R., Aitha, H., & Gotoor, S. G. (2014). Mucoepidermoid carcinoma. BMJ Case Reports, 2014, bcr2013202776. https://doi.org/10.1136/bcr-2013-202776
- Quyen, H.-T. D., Duc, N. M., Tuan, H. X., Tu, N.-H. T., Khoi, N. A., & Dung, P. X. (2023). Acinic cell carcinoma of parotid gland. Radiology Case Reports, 18(6), 2194–2198. https://doi.org/10.1016/j.radcr.2023.03.017
- Rosero, D. S., Alvarez, R., Gambó, P., Alastuey, M., Valero, A., Torrecilla, N., Roche, A. B., & Simón, S. (2016). Acinic cell carcinoma of the parotid gland with four morphological features. Iranian Journal of Pathology, 11(2), 181–185. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4939652/
- Carlson, E. R., & Schlieve, T. (2019). Salivary gland malignancies. Oral and Maxillofacial Surgery Clinics of North America, 31(1), 125–144. https://doi.org/10.1016/j.coms.2018.08.007
- Cantù, G. (2021). Adenoid cystic carcinoma. An indolent but aggressive tumour. Part B: Treatment and prognosis. Acta Otorhinolaryngologica Italica, 41(4), 296–307. https://doi.org/10.14639/0392-100X-N1729
- Zhang, M. H., Hasse, A., Carroll, T., Pearson, A. T., Cipriani, N. A., & Ginat, D. T. (2021). Differentiating low and high grade mucoepidermoid carcinoma of the salivary glands using CT radiomics. Gland Surgery, 10(5), 1646–1654. https://doi.org/10.21037/gs-20-830
- Gontarz, M., Urbańska-Gąsiorowska, M., Bargiel, J., Gąsiorowski, K., Marecik, T., Szczurowski, P., Zapała, J., & Wyszyńska-Pawelec, G. (2021). Sublingual gland neoplasms: Clinicopathological study of 8 cases. Medicina Oral, Patología Oral y Cirugía Bucal, 26(5), e626–e631. https://doi.org/10.4317/medoral.24634
- Adirajaiah, S., Anehosur, V., Sumana, & Gopalakrishnan, K. (2012). Adenocarcinoma of the sublingual salivary gland – A case report. Journal of Oral Biology and Craniofacial Research, 2(3), 206–209. https://doi.org/10.1016/j.jobcr.2012.10.004
- Vaidya, A. D., Pantvaidya, G. H., Metgudmath, R., Kane, S. V., & D’Cruz, A. K. (2012). Minor salivary gland tumors of the oral cavity: A case series with review of literature. Journal of Cancer Research and Therapeutics, 8 Suppl 1, S111-115. https://doi.org/10.4103/0973-1482.92224
- Noel, L., Medford, S., Islam, S., Muddeen, A., Greaves, W., & Juman, S. (2018). Epidemiology of salivary gland tumours in an Eastern Caribbean nation: A retrospective study. Annals of Medicine and Surgery, 36, 148–151. https://doi.org/10.1016/j.amsu.2018.10.039
- Pushpanjali, M., Sujata, D. N., Subramanyam, S. B., & Jyothsna, M. (2014). Adenoid cystic carcinoma: An unusual presentation. Journal of Oral and Maxillofacial Pathology : JOMFP, 18(2), 286–290. https://doi.org/10.4103/0973-029X.140796
- Sankar Vinod, V., Mani, V., George, A., & Sivaprasad, K. K. (2013). Polymorphous low-grade adenocarcinoma––management and reconstruction with temporalis myofacial flap. Journal of Maxillofacial & Oral Surgery, 12(1), 105–108. https://doi.org/10.1007/s12663-011-0227-8
- Boahene, D. K. O., Olsen, K. D., Lewis, J. E., Pinheiro, A. D., Pankratz, V. S., & Bagniewski, S. M. (2004). Mucoepidermoid carcinoma of the parotid gland: The Mayo clinic experience. Archives of Otolaryngology--Head & Neck Surgery, 130(7), 849–856. https://doi.org/10.1001/archotol.130.7.849
