Oral Congenital Melanocytic Nevi: A Rare Finding

AFFILIATIONS:
¹Assistant Professor of Family Medicine, Mayo Clinic Alix School of Medicine, Scottsdale, Arizona
²Instructor of Family Medicine, Mayo Clinic Alix School of Medicine, Scottsdale, Arizona

CITATION:
Bracamonte JD, Underhill M, Schweda D. Oral congenital melanocytic nevi: a rare finding. Consultant. 2023;63(2):e9. doi:10.25270/con.2022.10.000004

Received April 27, 2022. Accepted August 5, 2022. Published online October 5, 2022.

DISCLOSURES:
The authors report no relevant financial relationships. The authors report that informed patient consent was obtained for publication of the images used herein.

CORESPONDENCE:
Jesse D. Bracamonte, DO, Mayo Clinic Family Medicine, 20199 North 75th Avenue, Glendale, AZ 85308 (Bracamonte.Jesse@mayo.edu)

Case Presentation

A 44-year-old, non-smoking man presented to his primary care physician for an annual exam and reported having a deeply pigmented tongue lesion (Figure 1) that has been visible since childhood.

Figure 1. Clinical presentation of a lingual congenital melanocytic macule.

The patient’s past medical history was otherwise unremarkable. He did not smoke or drink and did not take any prescription medications or supplements. There was no family history of gastroenterologic pathology, melanoma, or additional skin pathology. He was born in India and his parents told him that the lesion has been visible since his infancy. He did not have associated pain, irritation, or difficulty with swallowing. The patient sought reassurance regarding any potential for malignancy.

Physical examination
At his physical examination, the patient’s oral lesion revealed a clearly demarcated hyperpigmented lesion of the dorsum of the tongue with color variegation. He demonstrated no lymphadenopathy on physical examination. There were no hyperpigmented lesions of hard palata, gingiva, or buccal mucosa. There were no additional skin lesions upon physical examination.

Differential diagnosis
The differential diagnosis of melanocytic nevi should include pigmented lesions of the mouth such as physiologic pigmentation, smoker’s melanosis, amalgam tattoo, and malignant melanoma.^1,3 Due to the size and history of the lesion, we restricted our diagnosis to melanocytic nevus with the need to rule out malignant melanoma.

Treatment and management

The cause of congenital melanotic macules is unknown, and no predisposing causative factors are known during gestation. The literature suggests that no biopsy is warranted for congenital lesions that remain unchanged since early childhood, however a biopsy may be required if the lesion presents minimal change in sequential monitoring.⁴

A malignant melanoma of the tongue is rare and thus a clinician must have a high index of suspicion for biopsy should changes occur. Transformation of a congenital melanocytic nevus has not been reported.² Oral melanocytic nevus does not require treatment if properly diagnosed and if the clinician can exclude additional worrisome etiologies, such as melanoma based on physical examination findings. Therefore, in this instance, we reassured the patient and did not move forward with treatment.

Discussion
Melanocytic nevi are congenital or acquired benign proliferation of cells of melanocytic origin.¹

The term congenital melanocytic nevus should be applied to benign melanocytic proliferation present at birth or early childhood. The lesion appears as a flat café-au-lait spot and may appear as dark macule or plaques. Satellite lesions are known to occur.  Clinical characteristics include solitary or multiple asymptomatic melanotic lesions on the tongue with subsequent proportional growth. The lesions tend to be more prominent in darker skinned individuals, but the cause is unknown.² Clinically these lesions tend to be homogenous in color and well-demarcated. Dimensions are reported to range from 0.1 to rarely 3.0 cm, with nevi measuring 0.5 cm being the most common.⁴ Dermoscopy reveals symmetric homogenous lesions and sometimes a regular pigmented network.⁴ Histopathologic findings show increased deposits of melanin in the basal cell layer, with a normal number of melanocytes and various degrees of hyperkeratosis.² Multiple oral congenital melanocytic nevi are a known risk factor for melanoma.⁵

Clinicians do not often encounter oral melanocytic lesions on the tongue. Although research on the topic is extremely limited, one study⁴ reported an incidence rate of 1 per 10,000 persons, with the most common locations being the hard palate, buccal mucosa, and vermilion border of the lip.

Our patient was initially referred to dermatology, but given his stability and long-standing history, no biopsy was indicated. He has been monitored annually by his primary care team without any changes to the lesion.

It is important for the clinician to ensure the lesion is long-standing and deemed evident since birth or early childhood. Although this lesion is entirely benign, it is imperative to determine if biopsy is warranted to rule out melanoma. Biopsy should be strongly considered in the event of color variegation such as with bluish or black changes or with minor changes in character.