Oral Nevi- Types, Causes, Symptoms and Treatment

What Are Oral Nevi?

Oral nevi are rare benign nevus cell proliferation in the epithelium, submucosal, or both layers of the mouth. They are divided into three categories: junctional, intramucosal, and compound nevi. Nevi are classified as either congenital or acquired. Oral nevi are typical lesions that commonly generate diagnostic difficulties. Brown or bluish nevi of the oral cavity are common, but achromic lesions are more common in fully intramucosal nevi. Nevi in the oral cavity are usually asymptomatic and are only discovered accidentally during a dental check-up.

What Is the Clinical Presentation of an Oral Nevus?

Oral nevi are clinically present as follows-

• Mostly solitary and asymptomatic.

• Well-circumscribed, round or oval macules or papules with a smooth surface.

• Dome-shaped mostly.

• Brown or bluish-colored lesions. Achromic lesions are present in the intramucosal nevi.

• The average size of the lesions is 0.3 cm to 0.5 cm, but larger lesions have been seen. Nevi that are larger than 6 mm are more likely to be congenital.

• Rarely turns into melanoma.

How to Differentiate Oral Nevi From Other Pigmented Lesions of Oral Cavity?

The following features can help to differentiate oral nevi from other pigmented lesions of the oral cavity-

• Melanotic macules and amalgam tattoos are typically flat, whereas oral nevi are raised in 80 % of cases.

• Ethnic pigmentation is almost always symmetric, not disturbing the surface topography and natural gingiva stippling.

• Only the anterior gingiva is affected by a smoker's melanosis, and a history of smoking is essential.

• Melanocytic proliferations do not blanch when compressed as the vascular lesions do.

• Diffuse patches of pigmentation, potential ulceration, nodularity, color variegation, and an uneven contour are all common features of malignant melanoma.

• Oral junctional nevi, atypical melanocytic hyperplasia, and malignant melanoma can all present with identical clinical symptoms, and lesions initially identified as oral junctional nevi may be atypical melanocytic hyperplasia.

What Are the Various Types of Oral Nevi?

The oral nevi have the following clinical and histological variants-

• Lentigo Simplex- A rare lesion. It can be present as a single or multiple nevi. Single lesions on the lips or gums are common.

• Junctional Nevus- Oral junctional nevi are uncommon and may be precancerous.

• Intramucosal Nevus- It is a rare disorder affecting the oral mucosa. The palate is the preferred position, followed by the cheek mucosa, lip, and tongue. Light brown, dome-shaped intramucosal nevi are common. This is the most prevalent kind, accounting for 64 % of all oral nevi documented.

• Compound Nevus- Intraoral lesions are infrequent, and the cause and origin are unknown. Because the clinical features of oral melanocytic nevus and oral melanoma are so similar, a histological examination is required for a conclusive diagnosis.

• Congenital Nevus- Congenital nevi are benign melanocytic proliferations that appear at birth, as well as lesions that show typical clinical and histological signs of congenital nevi but are not visible at birth. They are pretty rare.

• Blue Nevus- Blue nevi are a rare occurrence. In the submucosa or deep dermis, they exhibit benign proliferation of fusiform dermal melanocytes. Melanin granules are abundant in these cells. Predilection is seen on the hard palate. Blue nevi's risk of malignant transformation is unknown. The blue nevus is the second most prevalent kind of oral nevi, accounting for 16.5 % to 36 % of all oral nevi.

• Spitz Nevus- Intraoral Spitz nevi are uncommon, although they are common in the head and neck skin. Epithelioid and spindle cells reside in these nevi. Atypical Spitz tumors, Spitzoid melanoma, and conventional melanoma are possible misdiagnosis.

• Some rare other types of oral nevi include-

  • Neurotized nevi.

  • Combined nevi.

  • Balloon cell nevi.

  • Epithelioid blue nevi.

  • Plaque-type blue nevi.

  • Halo nevi.

How Are Oral Nevi Formed?

The neural crest gives rise to nevus cells. During development, these cells migrate to the skin and oral mucous membranes. Nevus cell development is thought to begin with melanocyte proliferation along with the basal cell layer and may be linked to rete ridge elongation. Contact inhibition is absent in nevus cells or lost shortly after the proliferation process begins. They store melanin pigment in nests called thèques. Nevus cells have the ability to move from the basal cell layer to the submucosa underneath it. They may eventually detach from the epidermis. Nevus cells may be restricted to the submucosa if junctional nests are lost later. The pigmentation of nevus cells decreases as they penetrate deeper into the submucosa.

What Is the Prognosis of an Oral Nevus?

Oral nevi has an excellent prognosis. It rarely comes back or turns malignant. A histologic sample is required in all oral melanocytic nevi, particularly those located in the palate, the most prevalent oral melanoma site. Patients should be educated to notice and report any changes in the oral cavity, particularly those that grow in size, and color, have nodularity, bleed, or ulceration.

What Are the Various Lesions That Resemble Oral Nevi?

Various focal or diffuse pigmented lesions that resemble oral nevi are-

• Focal Pigmented lesions of oral cavity-

  • Hemangioma.

  • Kaposi sarcoma.

  • Thrombus hematoma.

  • Varix.

  • Melanotic macule.

  • Mucosal melanoma.

  • Amalgam tattoo.

  • Melanoacanthoma.

  • Vascular malformation.

• Diffuse pigmented lesions of oral cavity-

  • Smoker's melanosis.

  • Physiological pigmentation.

• Post-inflammatory hyperpigmentation or hypopigmentation.

All these lesions must be considered the differential diagnosis of oral nevi as they present a very similar clinical appearance.

How Are Oral Nevi Diagnosed?

• The tests performed to diagnose oral mucosal nevi are almost the same as those for cutaneous nevi.

• Imaging is contraindicated. However, periapical radiography, which shows minute opaque particles, can distinguish an amalgam tattoo from a nevus.

• A biopsy should histologically examine all pigmented and non-pigmented oral lesions to confirm the nature of the lesion. Excisional biopsy is the primary diagnostic method. Lesions greater than 1 cm to 2 cm may require incisional biopsy.

What Is the Treatment for Oral Nevi?

The following steps can be taken for the management of oral nevus-

1. Medical Care- Oral examinations should be performed regularly to rule out malignant tumors.

2. Surgical Care- All melanocytic and amelanocytic lesions should be treated with caution in the oral cavity. The most reliable method for treating oral melanocytic lesions is complete excision. Excision and microscopic assessment are also required for evolving or recurrent lesions.

How to Prevent Oral Nevi?

Oral nevi are hard to prevent because they are not caused by sun exposure or other known causes.

Conclusion:

It is challenging to diagnose pigmented lesions of the oral cavity and the perioral tissues. In most cases, the clinical features of pigmented lesions in the oral cavity are sufficient for diagnosis. In some circumstances, however, a biopsy is required. Oral nevi are benign (non-cancerous) tumors of the mouth that only rarely become cancerous. Therefore, oral nevi has an excellent prognosis.