What is Oral Melanoacanthoma?

Oral melanoacanthoma is a rare and harmless condition that appears as a brown-black spot in your mouth. It usually doesn’t cause any symptoms and is known for appearing suddenly and growing quickly. It often occurs due to injury to the tissue inside your mouth and it tends to go away by itself over time. In most of the cases that have been reported in medical research, about 75% of them are described as responses to some type of damage.

If you have oral melanoacanthoma and the doctor examines it under a microscope, they’ll see a thickening of the top layer of your skin cells and a growth of melanocytes, which are cells that produce the pigment in your skin.

The most common place to find oral melanoacanthomas is the inner lining of the cheeks (buccal mucosa), but they can also be seen on the inner lining of the lips (labial mucosa), the roof of the mouth (palate), the gums (gingiva), the lining of the dental sockets (alveolar mucosa), and the back of the throat (oropharynx). There are two types: one that appears in many places (multifocal) and one that appears in a single place (singular), with the latter being the most common.

What Causes Oral Melanoacanthoma?

The cause behind oral melanoacanthoma, a pigmented lesion in the mouth, is not fully understood but it is often linked to injuries that activate melanocytes, the cells that produce the skin pigment melanin. Evidence supporting this theory includes finding a particular type of white blood cell, called eosinophils, shown on cell tissue examination which suggests a response to injury.

A review of 115 cases reported in 56 articles found that 77% of the researchers suggested the lesion is caused in response to an injury.

Long term exposure to trauma or chemical irritants tend to stimulate melanocytes, which can result in either changes in the color of the mouth area or lead to the development of a melanoacanthoma.

Regular use of products like toothpastes and mouthwashes which contain petroleum-based chemicals may act as irritants. Examples of these chemicals include sodium lauryl sulfate, phenolphthalein, nitrophenol, chlorophenol, phenylenediamine sulfate, amine fluorideco, and cocamidopropyl betaine. Using hydrogen peroxide mouthwashes too often can also irritate the inside of the mouth and could cause melanoacanthoma.

Dental fillings made of silver amalgam have also been said to possibly cause changes in the mouth’s appearance and pigmentation when used with other materials.

Other reported triggers include teeth grinding, constant cheek biting, poorly fitted dentures, implant surgery, and general long-term mouth injuries.

Patients treated for chronic asthma and those using ferrous lactate as a long-term treatment for iron-deficiency anemia also seem to have an increased risk of developing oral melanoacanthoma.

Risk Factors and Frequency for Oral Melanoacanthoma

Oral Melanoacanthoma is a condition that can happen at any point during an adult’s life, but it’s usually found in younger adults around the age of 35. More women get it than men, at a ratio of 3 to 2. It’s mostly seen in people with dark skin, followed by non-Hispanic whites and Hispanics. The disorder usually shows up as single lesions inside the cheeks, but sometimes it can appear as multiple lesions, mainly on the roof of the mouth.

Oral Melanoacanthoma can occur at any point during an adult’s life, but it’s more common in young adults around age 35.
Women are more likely to have it than men, at a ratio of 3 to 2.
People with dark skin are affected most, followed by non-Hispanic Whites and Hispanics.
Most often, you’ll see single lesions inside the cheek. If there are multiple lesions, they’re more likely to be on the roof of the mouth.

Signs and Symptoms of Oral Melanoacanthoma

Typically, if someone is having dark spots appearing in their mouth – usually brown or black, flat or raised – it could potentially be a cause for concern. Often, these spots appear on the inner cheeks, but they can also appear on the roof of the mouth, lips, and less commonly on the gums. They are generally painless, but there could be occasional discomfort or itchiness. There would usually be a record of newer mouth-care products, dental procedures, teeth grinding, vigorous tooth brushing or mouth injuries.

These dark spots can often be confused with melanoma due to their fast and radiating growth – a form of skin cancer that affects the mouth’s hard palate. Hence, it’s important to thoroughly examine the mouth and skin for multiple spots or suspicious dark patches. Generally, these spots naturally resolve with their growth stabilizing before retracting, but diffuse oral pigmentation – broad, uneven, and indiscriminate darkening – can also occur in rare cases.

Family history plays an important role as well. If there have been instances of dark, pigmented oral patches or multiple small growths in the intestines within the family, it could indicate Peutz-Jegher syndrome.

Comparatively, the roof of the mouth is more prone to developing multiple spots than lone ones. These multiple spots are usually darker and smaller in size. The count of these spots tends to fluctuate between two to five.

Testing for Oral Melanoacanthoma

Since oral melanoacanthomas don’t have any unique or recognizable signs, the diagnosis relies on findings from a tissue examination under a microscope, a process called histopathology. To confirm the presence of specific cells known as melanocyte dendritic cells, a special staining method using substances called S-100 and HMB-45 is used. This staining process is a helpful tool in making a confirmed diagnosis.

Treatment Options for Oral Melanoacanthoma

Oral melanoacanthoma is a harmless condition that doesn’t have a risk of becoming cancerous. That means once it’s diagnosed, there’s no need for further treatments. Some patients even find that after a small sample is taken from the growth for testing (known as an incisional biopsy), the lesion starts to get smaller.

If you still want it to be treated, the lesion can be removed with surgery. The surrounding healthy tissue will also be taken out to ensure that the whole lesion has been removed. This is known as having ‘negative margins’.

Other treatment options include Argon plasma coagulation, which is a method that involves using heated gas to remove the tissue, cryotherapy, which is extremely cold temperature to freeze and remove the tissue, and curettage, which is scraping the skin’s surface to remove the lesion. One can also use a topical cream, such as Fluorouracil 5%, which is a type of chemotherapy applied to the skin. However, these treatments are only recommended if the lesion causes any discomfort or for cosmetic concerns and are not routine procedures.

When a doctor needs to diagnose the cause of darkened spots or patches in the mouth, the possibilities can range from harmless conditions to rare oral cancer. A benign (non-cancerous) condition named oral melanoacanthoma usually shows up as a single spot, and in rare cases can show up in multiple places or more extensively.

These benign conditions caused by melanin (skin pigment) can be grouped into two types: those that show up multiple places (multifocal), and single spots (solitary). Multifocal pigmentation could be seen in people who smoke or use smokeless tobacco.

Sometimes, darker patches or spots showing up in multiple places can be caused by certain health conditions or medications. Potential causes could include:

HIV
Conditions like Peutz-Jeghers, neurofibromatosis, McCune-Albright syndrome, Addison’s disease, Laugier-Hunziker
Some drugs like azathioprines, antimalarials, cytotoxic agents like bleomycin, and contraceptives

Diffuse pigmentation not related to melanin could be due to heavy metals, trauma, or a condition known as hemochromatosis.

When assessing single spots of pigmentation, the most common diagnosis is a melanotic macule. Other possibilities include melanocytic nevus, and more rarely, oral cancer.

Addison’s disease can cause darker patches in the mouth due to increased production of a hormone that triggers pigment production. It happens when the adrenal glands (small glands on top of the kidneys) are not working well. Laugier-Hunziker syndrome is another rare cause for dark spots in the mouth and skin. It usually occurs in older white males and does not lead to other growths or cancers.

Some patients with HIV can develop dark spots or patches in their mouth, which is not related to antiretroviral therapy, CD4 counts, or how long they have had the disease.

Peutz-Jeghers syndrome (PJS) is a genetic condition associated with dark patches and small, benign growths in the digestive tract. It tends to appear during childhood. PJS patients usually have dark patches on their lips, inside the mouth, and around the mouth. If a patient comes in with dark patches inside or around the mouth and small growths in their digestive tract or a family history that suggests PJS, doctors should recommend genetic testing.

An amalgam tattoo or focal argirosis usually appears as a blue or grey tinge. These are located in the mouth near a previous dental filling, dental implant, or prosthesis. These patches can be seen on x-rays and a biopsy will show small black deposits in the tissue. When the patient’s history doesn’t clearly show a benign or non-melanin related cause, then a biopsy should be done.

Oral cancer should be suspected in cases where the spots meet the ABCDE criteria: Asymmetry, Border irregularity, changing Color, Diameter larger than 6mm, and Elevation or raised spots. Oral cancer makes up nearly a quarter of all head and neck cancers and often leads to poor survival rates due to its high chance of spreading and coming back. Because oral cancer can be serious, a biopsy should be performed to rule it out.

What to expect with Oral Melanoacanthoma

Oral melanoacanthoma is a condition that could fade away spontaneously or after a biopsy procedure. It could also clear up if any irritants causing it are removed. These lesions caused by oral melanoacanthoma might linger for periods ranging from several weeks to a year, and they might even grow or worsen before a patient seeks medical treatment.

In some instances, a single lesion could turn into multiple lesions or widespread pigmentation. However, there’s no record of this condition turning into cancer or presenting features of abnormal growth or development.

Possible Complications When Diagnosed with Oral Melanoacanthoma

Oral melanoacanthoma doesn’t typically result in any complications. However, if surgical removal is needed, there can be issues like scarring and pain after the operation.

It’s essential for oral surgeons to biopsy any pigmented spots in the mouth. This is because not doing so could potentially overlook a cancerous lesion. A biopsy should be performed unless the patient’s medical history clearly points to the cause of the pigmented lesion.

Recognized Complications:

Scarring after surgery
Post-operative pain
Potential missed cancer diagnosis

Preventing Oral Melanoacanthoma

Patients need to know that certain substances or dental implants could be linked to the development of oral melanoacanthoma, a matter that is usually harmless and will go away once exposure to the causing substance or implant is stopped.

In order to get this kind of information, it is very important for the doctor to ask about any non-standard dental substances or implants that have been used.

While oral melanoacanthoma is not harmful, it can look similar to oral melanoma which is a serious condition. Because of this, follow-up appointments are extremely important to ensure that it is indeed the harmless oral melanoacanthoma and not the more dangerous oral melanoma.