Introduction
Melanoma1 is a malignant neoplasm of melanocytes. The majority of these develop de novo and 30% evolve from previous nevi.
Epidemiology
Melanoma accounts for 8% to 11% of vulvar malignancies and 2% to 3% of all malignant melanomas in females. Vulvar melanomas occur more commonly in white women after menopause and are thicker and larger at the time of diagnosis than melanomas diagnosed elsewhere. A patient with a vulvar melanoma is usually 45 to 65 years of age.
Etiology
There is a strong genetic component to the disorder. 15-30% of patients who have vulvar melanoma have a family history of someone with melanoma. They are also highly likely to have atypical nevi in sites outside of the vulva.2
Symptoms and clinical features
Often patients do not notice the lesion until the melanoma reaches an advanced stage, presenting as a lump or mass, bleeding or itching. Less frequently, patients present with a “changing mole.”
Melanomas can involve the vulva anywhere, but 80% are on the mucous membrane (vestibule, labia minora and clitoris). The lesions may be quite large when finally discovered and diagnosed.
| Types of Melanoma |
|---|
| Superficial Spreading Melanoma—an elevated, variegated brown, blue-gray to black plaque with a very irregular border that typically has a slow horizontal growth phase then a vertical growth phase. It represents 50% of vulvar melanomas. |
| Nodular Melanoma—a rapidly growing melanocytic tumor with no horizontal growth phase, an aggressive vertical growth phase, and a poor prognosis. The two variants (nodular and nodular polypoid) of nodular melanoma together make up 35% of vulvar melanomas. |
| Acral Lentiginous Melanoma—a melanoma that occurs on palms, soles, nail beds, and the mucocutaneous skin of the mouth, genitalia, and anus. Sometimes, it has a discontinuous horizontal growth phase and is aggressive. However, it is relatively rare in whites, occurring more commonly in Asians and in patients with brown or black skin. It accounts for 15% of melanomas of the vulva. |
Superficial Spreading Melanoma.
This type appears as a flat, pigmented macule with a jagged border and a spectrum of colors—black, brown, red, gray. Nodular lesions may develop within the macule as time passes.
Nodular Melanoma.
There is a simple dermal nodule, 0.5 to 1 cm, with a homogeneous to slightly variegated color, blue-black, or reddish. This can ulcerate.
Acral Lentiginous Melanoma.
These look similar to lentigo maligna melanoma. They are initially flat with markedly variegated color (brown, black, blue, and depigmented areas) and ill-defined margins. Nodules eventually develop within the margins of the lesion. Margins are difficult to define for planning curative surgery.
Diagnosis
Clinical and histopathologic impressions determine the diagnosis. Prognosis is based on Clark’s levels of invasion, Breslow’s direct thickness measurement, and completeness of excision.3
Pathology/Laboratory Findings
Excisional biopsy is done if adequate margins and appropriate depth can be guaranteed. If the lesion is too big, an incisional biopsy can be done without risk of seeding the tumor.
Differential diagnosis
Differential diagnosis includes nevus, VIN, and mucosal melanotic macule.15
Treatment/management
Management and outcome depend on the histologic depth of the lesion and the completeness of removal. Treatment is surgical, requiring the expertise of the gynecologic oncologist. Frozen sections can be used to ascertain ulcer margins in recurrent acral lentiginous lesions.
Early superficial spreading melanomas less than 1.5 mm in depth of invasion have a relatively good outcome with radical wide local resection. These patients have the best chance for “cure.” Beyond that, surgery is combined with a variety of chemotherapeutic modalities. The best treatment is an early diagnosis and local removal. Surgery, radiation, and chemotherapy may provide some helpful palliative treatment for larger lesions. Palpably positive groin lymph nodes should be removed to prevent groin skin ulceration in the palliative phase of care of advanced disease.
References
- Fisher BK, Margesson, LJ. Genital Skin Disorders: Diagnosis and Treatment. Mosby, Inc., 1998. 214.
- Lynch P. in Pigmented Disorders, in Edwards L and Lynch P. Genital Dermatology Atlas, 2nd edition. Wolters Kluwer Health/Lippincott Williams & Wilkins, 2011. 242.
- Heller DS, Wallach RC (ed.) Vulvar Disease: a Clinicopathological Approach. Informa Healthcare USA, Inc., 2007.123-124.