Overview

A pleomorphic adenoma, also known as a benign mixed tumour, is the most common type of lump that grows in the salivary glands. Salivary glands are special glands in your head and neck that produce saliva, which helps with digestion and keeps your mouth moist. While these lumps are generally not cancerous (they are 'benign'), they are important to understand because they can grow over time and, in some cases, may turn into a cancer if left untreated.

Most pleomorphic adenomas develop in the parotid gland, which is the largest salivary gland located in front of and just below your ear. They can also occur in other salivary glands, such as the submandibular gland, which is found under your jaw. These tumours typically appear in middle age or later in life.

The name "pleomorphic adenoma" comes from its varied (pleomorphic) appearance under a microscope, as it's made up of different types of cells, specifically myoepithelial and ductal epithelial cells, which are found in the salivary glands. It's called a "benign mixed tumour" because it contains a mix of these different cell types and is not cancerous.

Although a pleomorphic adenoma is benign, it's crucial to manage it properly. It tends to grow slowly and painlessly, often without causing any noticeable problems for a long time. However, because it lacks a truly strong, clear outer layer (a 'capsule'), it can sometimes have tiny extensions that reach into the surrounding healthy tissue. This characteristic, along with the risk of it potentially turning cancerous over many years, makes careful diagnosis and treatment very important.

Symptoms and Causes

Symptoms

Pleomorphic adenomas are typically slow-growing and often don't cause any pain or other symptoms for a long time. This means you might not even notice it for many years. When symptoms do appear, they usually involve:

• A Lump or Swelling: The most common symptom is a noticeable lump or swelling, usually in the area of the parotid gland (in front of or below the ear) or under the jaw if it's in the submandibular gland.
• Slow Growth: The lump will typically grow very slowly over months or even years. You might notice it gradually getting bigger.
• Painless: The lump is usually painless. If you experience pain, rapid growth, or weakness in your face, it's important to see a doctor immediately, as these could be signs of a change in the lump.
• Firm, Solitary, and Mobile: When you feel the lump, it's usually firm to the touch, feels like a single lump (solitary), and can often be moved slightly under the skin. It's generally not tender when pressed.
• Normal Facial Nerve Function: In most benign cases, the lump does not affect the facial nerve, which controls the muscles of your face. This means your facial movements (like smiling, frowning, or closing your eyes) should remain normal.

Because these lumps are often asymptomatic (meaning they don't cause symptoms) for so long, they can sometimes grow quite large before they are discovered.

Causes

The exact reasons why a pleomorphic adenoma develops are not fully understood. We know that these tumours arise from specific types of cells within the salivary glands: the myoepithelial and ductal epithelial cells. These are the cells that normally make up the structure of the salivary glands and help them produce saliva.

For reasons that are not clear, these cells begin to grow abnormally, forming a lump. It's not caused by anything you've done or haven't done, and there are no specific lifestyle factors, diets, or environmental exposures that have been definitively linked to causing pleomorphic adenomas. They are not contagious and do not run in families in a typical inherited pattern.

Essentially, it's an abnormal growth of the normal cells that make up your salivary glands, but the trigger for this abnormal growth is currently unknown.

Diagnosis and Investigations

Diagnosis

Diagnosing a pleomorphic adenoma typically begins with a visit to your GP, who will then refer you to an Ear, Nose, and Throat (ENT) specialist. The diagnosis process involves several steps:

• Clinical Examination: Your doctor will carefully examine the lump in your neck or face. They will feel its size, shape, texture (whether it's firm or soft), and how mobile it is. They will also check for any tenderness. During this examination, the doctor will also assess your facial nerve function by asking you to make different facial expressions, such as smiling, frowning, and closing your eyes tightly. This helps to see if the lump is affecting the nerve, which is usually not the case with a benign pleomorphic adenoma.
• Medical History: Your doctor will ask you about your symptoms, including when you first noticed the lump, how quickly it has grown, and if you've experienced any pain or other changes. This information helps the doctor understand the nature of the lump.

Investigations

To get a clearer picture of the lump and confirm the diagnosis, several investigations may be carried out:

• Imaging Scans:
• • CT (Computed Tomography) Scan: This scan uses X-rays to create detailed cross-sectional images of your head and neck. It helps doctors see the exact size and location of the lump, whether it's pressing on any surrounding structures, and its general characteristics.
  • MRI (Magnetic Resonance Imaging) Scan: An MRI uses strong magnets and radio waves to produce very detailed images of soft tissues. It's particularly good at showing the extent of the tumour and assessing the integrity of its outer layer (capsule). This helps surgeons plan the best way to remove it.
• Fine Needle Aspiration (FNA) Biopsy: This is a common and very important test. A very thin needle is used to take a small sample of cells from the lump. This sample is then sent to a laboratory to be examined under a microscope by a pathologist. The FNA biopsy helps to determine if the lump is benign (non-cancerous) or malignant (cancerous), and often helps confirm if it's a pleomorphic adenoma. While very helpful, sometimes the full nature of the lump can only be confirmed after it has been surgically removed and examined.

These investigations help your medical team understand the lump fully, allowing them to make an accurate diagnosis and plan the most appropriate treatment for you.

Management and Treatment

The primary and most effective treatment for a pleomorphic adenoma is surgical removal. This is crucial not only to remove the existing lump but also to prevent it from growing larger, recurring, or potentially turning cancerous in the future.

• Surgical Excision (Surgical Removal):
• • Complete Removal is Key: The goal of surgery is to completely remove the tumour along with a small margin of surrounding healthy tissue. This is known as a "wide excision." Unlike some other benign lumps that have a very clear, strong outer layer, a pleomorphic adenoma's outer layer (or 'capsule') isn't always complete. It can sometimes have tiny finger-like projections that extend into the healthy tissue nearby. For this reason, simply scooping out the lump (a procedure called 'enucleation') is not enough, as it leaves a high risk of the tumour growing back.
  • Parotidectomy: If the tumour is in the parotid gland, the surgery is called a parotidectomy. This involves removing part or all of the parotid gland, depending on the size and location of the tumour.
  • Preserving the Facial Nerve: The facial nerve runs through the parotid gland and controls all the muscles of your face. During parotid surgery, the surgeon takes great care to identify and preserve this nerve to avoid any weakness or paralysis of your face. In some cases, especially if it's a repeat operation, a special monitor may be used during surgery to help protect the nerve.
  • Preventing Recurrence and Malignant Transformation: Meticulous initial surgical removal is vital. If the tumour is not completely removed, or if it spills during surgery, there is a higher chance of it growing back (recurrence). Recurrent tumours are often more challenging to treat because they can appear in multiple places (multifocal) and carry a higher risk of further recurrences and malignant transformation (turning cancerous).
• Adjuvant Radiotherapy (Additional Radiation Treatment):
• • In certain situations, after the tumour has been surgically removed, your medical team might consider additional treatment with radiotherapy. This is called 'adjuvant radiotherapy' because it's given after the main treatment (surgery) to reduce the risk of the tumour coming back.
  • This may be considered, for example, in elderly patients, or if the tumour was very large, if there was gross wound contamination (tumour cells spilled during surgery), or if you have a recurrent tumour that has appeared in multiple places.
  • The decision to use adjuvant radiotherapy is always made after a detailed discussion with a multidisciplinary team (MDT), which is a group of specialists including surgeons, oncologists (cancer doctors), and radiologists, who work together to decide on the best treatment plan for you.
• Conservative Management (Observation):
• • For some individuals, particularly those who are very frail or have other serious health conditions that make surgery risky, conservative management might be an option. This means closely monitoring the lump with regular check-ups and scans, rather than immediate surgery. However, it's important to understand that choosing conservative management means accepting the risks that the lump will continue to grow and that there is a small but significant risk of it turning cancerous over time. This decision would be made after a thorough discussion with your medical team about the potential benefits and risks.

Prevention

Currently, there are no known specific ways to prevent a pleomorphic adenoma from forming in the first place. These tumours arise from the normal cells of your salivary glands for reasons that are not fully understood, and they are not linked to lifestyle choices, diet, or environmental factors that you can control.

However, while you cannot prevent the initial development of a pleomorphic adenoma, you can take important steps to prevent its potential complications and ensure the best possible long-term health outcome:

• Early Detection: If you notice any new lump or swelling in your neck, in front of or below your ear, or under your jaw, it is important to see your GP promptly. Early detection allows for timely diagnosis and treatment, which is key to preventing the lump from growing larger and reducing the risk of it turning cancerous.
• Complete Surgical Excision: Once a pleomorphic adenoma is diagnosed, the most effective way to prevent its growth, recurrence, and malignant transformation (turning cancerous) is through complete surgical removal. Following your surgeon's advice for a thorough excision is the best preventative measure against future problems related to the tumour.
• Adherence to Follow-up: After treatment, attending all your scheduled follow-up appointments is crucial. This allows your medical team to monitor your recovery and check for any signs of recurrence or new issues, ensuring that any potential problems are caught and addressed early.

By being aware of your body and seeking medical advice for any new lumps, and by following through with recommended treatment and follow-up, you are taking the most important steps to prevent the complications associated with pleomorphic adenoma.

Outlook / Prognosis

The long-term outlook for individuals with a pleomorphic adenoma is generally very good, especially when the tumour is completely removed through surgery. Complete surgical removal offers excellent cure rates, meaning most patients will not experience further problems with the tumour. With appropriate surgical techniques and diligent long-term surveillance, most patients achieve excellent functional outcomes and can live full, healthy lives after being treated for a pleomorphic adenoma.