Types of Oral Pigmented Lesions - An Overview

What Are Oral-Pigmented Lesions?

Oral-pigmented lesions are mostly benign lesions (non-cancerous) present in the oral mucosa. Such oral-pigmented lesions are classified based on pathological, physiological or endogenous, or exogenous types. They may also be classified based on the underlying cause of the lesion, their occurrence, color, nature of the lesion, their link between the use of drugs, family history, and even the health pattern of the affected individual. Determining the underlying cause of the lesion is necessary to distinguish them from other oral lesions. Darkly pigmented lesions are classified as focal, multifocal, or diffuse lesions. Melanin, which is produced in these lesions is formed by the cells called melanocytes. They are present in the basal layer of the skin or epithelium. The pigment or color is transferred to the adjacent keratinocyte cells via the cell membrane-bound organelles known as melanosomes.

Some common examples of these lesions include:

• Melanocytic nevus.

• Blue nevus.

• Smoker’s melanosis.

• Oral melanoacanthoma.

• Drug-induced pigmentations.

• Pigmentated lesions of systemic manifestations like Peutz-Jeghers syndrome, and Addison´s disease.

What Are the Different Types of Oral Pigmented Lesions?

A. Physiological Pigmentation: Physiological pigmentation is one of the most common oral pigmentation.

• This lesion mainly results from the increase in the melanin pigment and is more commonly noted in dark-skinned individuals.

• The color of physiological pigmentation would usually range from a light brown to a blackish color.

B. Post-inflammatory Pigmentation: Long-term or chronic inflammatory oral mucosal conditions like oral lichen planus (a chronic condition that causes a patchy white lesion in the oral mucosa), pemphigus (an autoimmune disease causing blisters of the skin, mucosal regions of oral cavity and nose), or pemphigoid (an autoimmune condition causing fluid-filled blisters in the skin and oral mucosa) may result in these types of inflammatory mucosal pigmentation.

• These lesions are characterized by multiple small brown, or black-pigmented area located in the oral mucosa.

• They are generally present adjacent to reticular, erosive, or vesicular lesions of the oral cavity.

C. Melanotic Macule: The oral melanotic macules are common and rather small, well-circumscribed lesions that are brownish-black in color.

• These lesions are located mainly on the lips, and the gingiva.

• They might also occur on the palate and buccal mucosa.

• People suspected of having these lesions are generally advised to do a biopsy study to distinguish it from other drug-induced or systemic melanocytic lesions.

D. Melanocytic Nevus: These nevi are comparatively unusual and less common on the oral mucosa. They tend to occur more on the epithelium or the skin.

• Melanocytic nevus of the oral cavity is a very small circumscribed yet raised macules or papules.

• These nevi can range from bluish-gray to almost black. And occasionally they may occur as non-pigmented lesions.

E. Blue Nevus: This lesion is a benign form of melanocytic lesion that occurs in the oral cavity and presents without any symptoms.

• The lesions are usually slate-blue or blue-black with a smooth surface resembling macules or papules.

• These lesions typically measure less than six millimeters (mm) in diameter with the characteristic blue color, hence are called a blue nevus.

• These lesions are more commonly seen in females than in males.

• Two-thirds of all intraoral blue nevi are commonly found at the location of the hard palate while the buccal mucosa is the second-most common site.

F. Smoker’s Melanosis: This is a global condition that occurs in nearly 25 to 31 percent of all tobacco users worldwide.

• This condition is typically characterized by the presence of multiple discrete or coalescing macules that are brown in color.

• They generally involve the attached mandibular gingiva (gums attached to the lower teeth) and the labial side (the front portion) of the mouth. It is very common to see smokers' melanosis pigmentation located on the palate and the buccal mucosa.

• Recent studies show the association between discrete smokers' melanosis with pipe smoking habits.

• In cases of smoking-associated melanosis of the oral mucosa, the increased melanin production by the melanocytes and subsequent deposition in the basal cell and lamina propria layer (a layer of connective tissue that forms the mucosa) makes them evident for the diagnosis.

• The presence of a habitual history of smoking makes the diagnosis easier in cases of smokers' melanosis.

G. Black Hairy Tongue: This type of lesion is characterized by the involvement of the tongue and is relatively painless and benign.

• These lesions are caused due to defective desquamation or reactive hypertrophy that arises within the filiform papillae of the tongue.

• The keratinized filiform papillae get elongated giving the hairy appearance of the tongue.

• They may exhibit various colors upon pigmentation ranging from yellow-brown to black.

• The pigmentation of these lesions depends on various factors such as tobacco, smoking, coffee or tea consumption, and other intrinsic factors such as the involvement of chromogenic organisms in the normal oral flora resulting in pigmentation.

H. Foreign Body-Induced Pigmentation: Pigmentations of the oral mucosa may occur due to exposure to metals such as:

• Lead Pigmentation: A generalized cutaneous ‘lead huge lines’ occur upon the gingiva manifesting rather as grey areas of discoloration under the gingival margins.

• Mercury Pigmentation: Resulting in slate gray gingival hyperpigmentation.

• Amalgam Pigmentation: This is similar to other common metal pigmentations caused by the presence of amalgam material in the oral tissues.

I. Drug-induced Pigmentation: Drugs like arsenic commonly hold the potential for inducing pigmentation in the epidermal cells of the skin or oral mucous membranes by promoting the action of the tyrosinase enzyme.

• Other drugs like Phenothiazines and Minocycline may also gets deposited in the skin or in oral mucosa that directly reacts with melanin to form a drug–pigment complex.

• Clotrimazole and Tetracycline drugs are similarly found to be the most common drug associated with oral pigmentation according to dental research.

• Ketoconazole, Pyrimethamine, and Barbiturates similarly are other oral pigmentation-inducing drugs in some Individuals.

J. Peutz-Jeghers Syndrome (PJS): This systemic disease is characterized by mucocutaneous macules and intestinal polyposis. The patient affected by this condition suffers an increased risk of cancer in the gastrointestinal tract, pancreas, breast, or thyroid glands. Orally, the lesions are pigmented as brown or black spots that are less than one mm in size that are localized typically to the lower lip and in the perioral areas.

K. Systemic Diseases Pigmentation: Pigmented lesions related to other systemic diseases that may also be present in the oral mucous membrane or gingiva include:

• Addison disease (a chronic condition causing insufficient production of certain hormones by the adrenal gland).

• McCune-Albright syndrome (a genetic condition affecting the bone, skin, and endocrine system).

• Hyperthyroidism (a condition with excessive production of thyroid hormone by the thyroid gland).

• Nelson syndrome (a life-threatening condition often causing vision loss, pituitary failure, and dark skin pigmentation).

These lesions may either be diffuse or localized in the oral mucous membrane or gingiva.

Conclusion:

Numerous oral pigmented lesions exist because of local or oral diseases or as a result of oral manifestations of systemic diseases. These lesions can be clinically diagnosed by the dentist and ruling out other differential diagnoses such as oral cancers is essential for the diagnosis and treatment planning.