Pigmented Lesions of Oral Mucosa

Pigmented Lesions of Oral Mucosa

• Endogenous pigmentation is most commonly caused by hemoglobin, hemosiderin, and melanin.
• Major exogenous factors include traumatic deposits, ingested/inhaled substances, spread via the bloodstream, certain foods/drinks, and chromogenic bacteria.
• Endogenous pigmentation can be classified as focal, multifocal/diffuse, or idiopathic, and can sometimes be associated with systemic/genetic diseases.
• Types of Exogenous Pigmentation include: Amalgam Tattoos, Graphite Tattoos, Heavy Metal Pigmentation, and Drug-Induced Pigmentation. A further type is Hairy Tongue.

Endogenous Pigmentation: Melanin

• Melanin is a pigment derived from tyrosine, synthesized by melanocytes.
• Melanocytes reside in the basal cell layer of the epithelium.

Focal Melanotic Pigmentation

• Freckles/Ephelis are asymptomatic, well-circumscribed, tan or brown macules often found in sun-exposed areas of the skin.
• Oral/Labial Melanotic Macule is a unique, benign, pigmented lesion without a known dermal counterpart. It's the most common oral lesion of melanocytic origin, often found on lower lips and gingiva in adults.
• Oral Melanoacanthoma is a reactive lesion.
• Melanocytic Nevus is a benign lesion, commonly presenting as a solitary lesion and it often appears in the buccal mucosa and gingiva.
• Malignant Melanoma is a rare, though serious, lesion often presenting as a dark-pigmented flat or slightly elevated lesion.
• Oral Melanotic Macule is typically small (<1mm). It's oval or irregularly-shaped and uniformly pigmented.
• Oral melanoacanthoma is an innocuous melanocytic lesion that may spontaneously resolve.
• It is typically rapid onset, usually following an instance of acute or chronic irritation, and is rapidly enlarging.

Melanocytic Nevus

• Nevi arise as a consequence of melanocytic growth and proliferation.
• Their etiology involves both genetics and environment.
• Nevi, in general, are acquired or congenital, true benign neoplasms, or developmental in nature.
• The possibility of genetic susceptibility to nevus development exists, linked to several inherited diseases.
• There is ongoing debate as to whether "nevus cells" are a distinct, neural-crest-derived cell type or a specialized form of melanocyte.

Oral Melanocytic Nevi

• Oral melanocytic nevi have no distinguishing clinical characteristics and are typically asymptomatic, solitary, brown or blue macules.
• Lesions most often present as a small, well-circumscribed nodule or macule.
• The hard palate, labial mucosae and gingiva are common sites for melanocytic nevi.

Malignant Melanoma

• Malignant melanoma is the least common, but most deadly, primary cancer.
• It is associated with a range of extrinsic and intrinsic factors in its pathogenesis, including a history of multiple episodes of or acute sun exposure and immunosuppression. There is also a role for mutations related to several tumor suppressor genes and MC1R polymorphisms as well as a family history of melanoma.

Challenges in Diagnosing Pigmented Lesions

• It is important to determine if a lesion is a primary neoplasm or a metastatic source from a distant site
• A history of previous melanoma, sparing of the palate and gingiva, and the absence of junctional activity may suggest a metastatic tumor.
• CT and MRI are essential for examining for metastatic sites to the regional lymph nodes.

Multifocal/Diffuse Melanotic Pigmentation

• Physiologic Pigmentation is a common finding in dark-skinned individuals, and it is often restricted to the gingiva. The pigments is typically first observed during childhood and does not develop de novo in the adult.
• Drug-Induced Pigmentation: caused by drugs such as minocycline, it can be seen on the oral/skin/nails and usually resolves in within a few months after stopping the drug.
• Smoker's Melanosis is usually associated with a history of smoking.
• Postinflammatory (Inflammatory) Hyperpigmentation: occurs in areas subjected to previous injury or inflammation.
• Melasma (Chloasma): refers to an acquired symetric melanosis that is common and typically occurs on sun-exposed areas of the skin, especially in women and often during pregnancy.

Melanosis Associated with Systemic or Genetic Disease

• Various systemic conditions including, hypoadrenocorticism, Cushing's syndrome, hyperthyroidism, primary biliary cirrhosis, vitamin B12 deficiency, Peutz-Jeghers syndrome, HIV/AIDS, and café au lait pigmentation, may be associated with melanosis.
• Etiology of these conditions includes adrenal destruction, autoimmune conditions, infections, neoplasia, trauma, and/or exposure to certain medication (iatrogenic conditions).
• Reduced corticosteroid levels sometimes also need to be considered when evaluating these conditions.

Microscopically Pigmented Lesions

• Increased amounts of melanin in the basal cell layer, often with basilar hyperpigmentation.

Drug-Induced Melanosis

• Drug-induced melanosis can be diffuse or localized to one oral surface, often affecting the hard palate, or it can be multifocal and affect multiple areas.
• The lesions typically appear flat, without nodularity or swelling.
• Sun exposure can intensify the pigmentation
• Microscopically, there is evidence of basilar hyperpigmentation and melanin incontinence without a concomitant increase in melanocytes number.
• Laboratory tests may be required to rule out endocrinopathies in cases of suspected drug-induced melanosis.

Depigmentation (Vitiligo)

• Vitiligo is a disorder caused by autoimmune destruction of melanocytes, leading to hypomelanosis.
• While its etiology is unknown, it has been associated with autoimmunity, cytotoxicity, genetics and oxidative stress.
• Vitiligo rarely affects the oral mucosal tissues.

Hemoglobin and Iron-Associated Pigmentation

• Ecchymosis, purpura/petechiae, and/or hemochromatosis can all cause extravasated blood in tissues, organs or spaces.
• extravasated erythrocytes degrade to form hemosiderin which can lead to a bluish-brown discoloration in tissues.
• Clinically, ecchymosis is characterized as a flat, dark discoloration that can occur on both superficial dermal and mucosal layers. It's more common on the face than on the lips. Although rarely seen intraorally, it can be seen with blunt trauma, oral intubation, or leukemia. Diagnosis often involves differentiating ecchymosis from other intraoral pigmented/lesional types.

Exogenous Pigmentation

• Amalgam tattoos, graphite tattoos, heavy metal pigmentation, drug-induced pigmentation, and hairy tongue.

Amalagam Tattoos

• Amalagam tattoos are the most common pigmented lesion in the oral mucosa, caused by the iatrogenic deposition of amalgam material into the submucosa.
• These lesions commonly occur in the gingiva and alveolar mucosa, near amalgam fillings, and are best detectable via radiographs.
• While the lesion is often asymptomatic, its appearance can usually be characterized as a small, asymptomatic, bluish-gray or black macule.

Graphite Tattoos

• Graphite tattoos appear due to the traumatic implantation of graphite particles (e.g., from pencils).
• These lesions exhibit a similar appearance to amalgam tattoos but are not usually visible on radiographs.

Other Pigmented Lesions

• Further pigmented lesions (e.g.,Café au Lait, Idiopathic/Laugier-Hunziker, etc) are also addressed throughout the notes.

Test your knowledge on the various pigmented lesions of the oral mucosa, including endogenous and exogenous pigmentation factors. Learn about melanin synthesis, classifications of pigmentation, and specific types such as amalgam tattoos and hairy tongue. This quiz is essential for understanding oral health and related systemic conditions.