Pigmented spots resembling moles can occur inside the mouth. These spots are relatively common, and the majority are entirely harmless, representing normal variations in oral tissue pigmentation. However, the oral cavity is a site where a rare but serious form of melanoma can develop. Therefore, any new, changing, or unexplained dark spot requires professional evaluation to determine when to seek a definitive diagnosis.
Common Causes of Pigmentation in the Mouth
The majority of dark spots found in the mouth are benign and arise from four main categories, each with a distinct cause and appearance.
Oral Melanotic Macule
One frequent finding is the oral melanotic macule, often described as an oral freckle. These lesions appear as flat, well-defined, uniformly colored brown-to-black patches, typically measuring less than seven millimeters. They result from a localized increase in melanin production by pigment-producing cells without an increase in the number of those cells.
Physiological Pigmentation
Many individuals also exhibit physiological or racial pigmentation, which is a normal, genetically determined increase in melanin deposition across the oral tissues. This type of pigmentation is frequently seen in individuals with darker skin tones. It usually presents as multiple, diffuse, and symmetrical brown or black patches, most commonly affecting the gums and cheek lining.
Amalgam Tattoo
Another common occurrence is the amalgam tattoo, caused by the accidental implantation of metallic silver-amalgam particles into the soft tissue during dental procedures. These spots are typically flat and present as a distinct blue, gray, or black discoloration, often located near a tooth that has or previously had a silver filling. The color is stable, and the metallic particles may sometimes be visible on a dental X-ray.
Oral Nevi
True oral nevi are the equivalent of a mole on the skin. They are less common than macules or amalgam tattoos but are also benign. These spots form from a collection of specialized pigment cells called nevus cells. Oral nevi can be flat or slightly raised, ranging in color from light brown to black, with the hard palate being one of the most common locations.
Recognizing Potentially Concerning Changes
While most oral pigmented spots are harmless, the rare possibility of oral melanoma requires vigilance. Oral melanoma is an aggressive cancer that often affects the hard palate or the gums. Tracking changes in a pigmented spot should be guided by criteria similar to those used for skin lesions:
- Asymmetry: One half of the spot does not match the other half in shape or color.
- Border irregularity: The edges are blurred, notched, or ragged, rather than smooth and well-defined.
- Color variation: The presence of multiple shades of color, such as black, brown, gray, red, or a loss of pigment within the same lesion.
- Diameter: A size greater than six millimeters, which raises suspicion, although early melanomas can be smaller.
- Evolution or Elevation: Any notable change over a short period, including a sudden increase in size, change in shape, or becoming raised or nodular.
The development of ulceration or bleeding within the spot also warrants immediate professional attention.
Clinical Diagnosis and Monitoring
When a pigmented lesion is identified, the diagnostic process begins with a thorough clinical examination by a dentist or oral specialist. This assessment includes a detailed patient history, focusing on the lesion’s duration, recent changes, and related symptoms. Clinical photography is used to create a permanent, objective record of the spot’s size, color, and precise location. This photographic mapping allows the healthcare provider to accurately track even subtle changes over time.
Biopsy Procedures
If the lesion is small and appears clinically benign, the provider may elect to perform an excisional biopsy. This involves removing the entire spot along with a small margin of surrounding healthy tissue. This procedure is both diagnostic and therapeutic, ensuring the entire lesion is analyzed by a pathologist. Conversely, if a lesion is large or if there is a strong suspicion of malignancy, an incisional biopsy is preferred. Only a representative sample is taken for initial diagnosis, avoiding complication of a larger surgical procedure.
Treatment Outcomes
For lesions definitively diagnosed as benign, such as an oral melanotic macule or amalgam tattoo, no further treatment is typically needed. The protocol shifts to regular periodic monitoring. If a diagnosis of oral melanoma is confirmed by the biopsy, the primary treatment is aggressive surgical excision to remove the tumor with wide, disease-free margins. Depending on the stage of the cancer, this surgery may be followed by additional treatments like radiation therapy or immunotherapy.