Moles and other pigmented spots can appear inside the mouth, often surprising people. Any dark area on the gums, palate, or inner cheek is medically termed an oral pigmented lesion. The vast majority of these lesions are harmless, occurring because the mouth contains melanocytes, the same pigment-producing cells found in the skin. Recognizing specific visual features helps distinguish a common spot from one that warrants professional attention.
What Are True Oral Moles?
A true mole in the mouth is medically termed an oral melanocytic nevus, representing a benign growth of pigment cells. These oral lesions are relatively rare, with a reported prevalence ranging from 0.1% to 0.5% in the general population. They are typically small, less than one centimeter in diameter, and remain stable over time.
These nevi often appear as a solitary spot that is brown, blue, or black, and can be flat or slightly raised. The most common sites for oral nevi are the hard palate and the gingiva. The most frequent subtype is the intramucosal nevus, a collection of nevus cells deep within the connective tissue.
Oral melanotic macules, the “freckles of the mouth,” are far more common than true nevi. Macules are flat spots resulting from increased melanin production, not an increase in melanocyte number. Because differentiating a benign nevus from an early-stage melanoma can be challenging, a biopsy is often recommended for any solitary, newly discovered pigmented spot.
Other Common Dark Spots Mistaken for Moles
Many dark spots found in the mouth are benign pigmentations rather than true moles or nevi. These common spots are often related to natural processes or foreign materials introduced into the oral tissues.
Physiological/Racial Pigmentation
This type of pigmentation is a naturally occurring variation that is common in individuals with darker complexions, including those of African, Asian, and Mediterranean descent. It is caused by increased activity of melanocytes, leading to more melanin production, rather than an increase in the number of pigment cells. The pigmentation is typically diffuse and involves multiple areas of the mouth, most often appearing as patchy to generalized brown or black discoloration on the gums. It is usually first noticed during childhood or adolescence and does not appear suddenly in adulthood. This generalized pattern helps distinguish it from a solitary mole or a concerning lesion.
Amalgam Tattoos
Amalgam tattoos are the most common cause of localized oral pigmentation and are entirely harmless. They occur when tiny fragments of silver-colored dental filling material, an alloy of silver, tin, copper, and mercury, become embedded in the soft tissues of the mouth. This typically happens during the placement, polishing, or removal of an amalgam filling. The lesions present as a flat, painless spot that is typically blue, gray, or black. They are often found on the gums or inner cheek near a tooth that has or once had an amalgam restoration. The diagnosis can sometimes be confirmed by a dental X-ray if the metal particles are large enough to be visible.
Post-Inflammatory Pigmentation
Chronic irritation or inflammation in the oral cavity can sometimes leave a temporary dark mark known as post-inflammatory pigmentation. This discoloration results from an excess of melanin being produced and deposited in the basal layer of the tissue as a response to the inflammatory process. Conditions such as oral lichen planus or chronic trauma can lead to this type of pigmentation. Clinically, the spots are brown and may have irregular margins, often resolving once the underlying cause of inflammation is treated.
Recognizing High-Risk Changes
While most dark spots are benign, any new, solitary, or changing pigmented lesion must be professionally evaluated to rule out oral melanoma, a rare but aggressive form of cancer. Early detection significantly affects the outcome. Standard criteria used for skin lesions are adapted to assess suspicious spots in the mouth, focusing on the lesion’s characteristics:
- Asymmetry: One half of the lesion does not mirror the other half if an imaginary line is drawn through the middle. Normal moles tend to be symmetrical.
- Border: Assess the edges for irregularity, looking for notched, ragged, or poorly defined margins, which contrasts with the smooth, well-defined border of a benign spot.
- Color: Benign lesions are typically a uniform shade, whereas concerning lesions may exhibit a mixture of colors, such as varying shades of brown, black, blue, red, or white.
- Diameter: Most melanomas are larger than 6 millimeters, roughly the size of a pencil eraser, though size alone is not definitive.
- Evolution: This refers to any noticeable change in the lesion over a short period, including changes in size, shape, color, or height. New symptoms like bleeding, ulceration, or unexplained pain within the pigmented area also require immediate attention.
If a spot meets any of these criteria, a dental professional or oral pathologist will typically recommend a biopsy for definitive diagnosis.