Melanosis of the Vagina: A Case Report

Purpose: To report a rare case of melanosis of the vagina. Methods: Case Report Introduction: Melanosis describes an abnormal deposition or development of melanin pigment in the basal layer of squamous epithelium. Melanosis is relatively common in the oral and gastrointestinal tracts, but it is a relatively uncommon finding in the female genital tract with most reported cases located in the vulvar region. Melanosis of the vagina is a particularly rare, benign pathology. Only a few cases have been reported in the literature. The etiology of vaginal melanosis is unclear; however, one prominent theory explains that this pathogenesis is due to the excessive migration of pigmented cells of neural crest origin. Other theories include pathogenesis occurring in response to chronic irritation or trauma. On gross visual inspection, vaginal melanosis can have a striking resemblance to malignant melanoma. Melanosis typically presents with the classic ABCDE criteria (Asymmetry, irregular Border, non-uniform Color, Diameter > 6mm, and Evolution) associated with melanoma, making the diagnosis difficult to distinguish clinically. Melanosis of the vagina usually presents in women over the age of 40, while vaginal melanoma has a peak incidence in females between the age of 50-60 years old and comprises 1-5% of total vaginal malignancies. Therefore, a biopsy of the lesion is indicated to rule out potential malignancy and formulate an appropriate treatment plan. Case: A 41-year-old G4P3013 African American woman was referred to the gynecologic clinic after her primary care physician noted hyperpigmented lesions throughout the vaginal canal during an annual examination. She had a history of persistent hyperpigmented vaginal lesions that were biopsied four years prior and reported to be benign, normal mucosa. The patient was being followed with annual examinations, which noted no change in size, color, or contour of the lesions. Her medical history was only significant for obesity. The patient was up-to-date on annual examinations and cervical cancer screening. All previous pap tests had resulted as negative for intraepithelial lesions and malignancy (NILM) and negative for high-risk HPV. The patient endorsed regular, monthly periods with no abnormal bleeding or vaginal discharge. On gynecological examination, multiple brown-black irregular bordered hyperpigmented lesions were noted on the anterior vagina, right vaginal wall, and posterior vaginal wall. The vaginal lesions were flat without induration or tenderness. The cervix was normal in appearance. After a discussion with the patient, she was referred to the vulvar clinic for biopsy of the lesions. The surgical pathology report revealed squamous mucosa with basal hyperpigmentation. No dysplasia or carcinoma was identified. The patient was informed of the benign biopsy results and was advised to continue to follow up with annual examinations. Conclusion: Melanosis of the vagina is typically an incidental finding presenting as a macroscopic hyperpigmented lesion on speculum examination. Otherwise, this anomaly is clinically asymptomatic. Due to the close resemblance of vaginal melanosis to malignant melanoma, it is crucial to consider biopsy, as histological analysis can effectively exclude malignancy. While our case presented benign melanotic vaginal lesions, the etiology and evolution of these lesions is not well studied due to the scarcity of reported cases. Although vaginal melanosis is non-invasive, past cases have shown that it carries a potential risk for transformation into malignant melanoma. This highlights the need for a strict follow-up protocol including continued close observation after initial histological confirmation.