FINAL DIAGONOSIS: PRIMARY MALIGNANT MELANOMA OF THE VAGINA
Malignant melanoma of the vagina is a rare entity, first reported by Poronas in 1887. It represents less than 3-5% of malignant neoplasms of the vagina. It is presumed to arise from melanocytes found in the vagina of 3% of normal women. It may occur at any age but is mainly a disease of postmenopausal women with 75% of patients being 50 and older. Presenting symptoms include vaginal bleeding, discharge and a mass. It may arise anywhere within the vagina with a predilection for the distal third.
Cytologically, the smear shows abundant cellularity with bloody background. The melanoma cells demonstrate a dispersed single cell pattern, loosely cohesive groups or 3 dimensional tissue fragments. Epithelioid cells, giant cells, binucleated or multinucleated cells, plasmacytoid cells, spindle cells, clear cells and signet ring cells are seen. The nuclei are pleomorphic with macronucleoli and intranuclear inclusions. Double mirror image nuclei "demons" are sometimes present. The cytoplasm is abundant and granular with or without melanin pigment.
Grossly, the tumor appears as black or grayish black nodular, polypoid or fungating masses. Only 6% of these tumors are amelanotic. Frequently, the overlying epithelium is eroded or ulcerated which helps to explain their frequent confusion with squamous cell carcinoma.
Microscopically, the lesion shows proliferation of atypical melanocytes along the dermoepidermal junction with extension into the squamous epithelium. The atypical melanocytes may be epithelioid, spindled or mixed and occur singly or in clusters. The infiltrative component is usually nevoid or spindled. Determination of the tumor thickness is based on a system proposed by Chung et al. since Clark's levels are inappropriate for mucosal sites of melanoma. The system is as follows: Level I-tumor confined to the surface epithelium, Level II-invasion of 1 mm or less, Level III-invasion of 1-2 mm and Level IV-invasion of greater than 2mm. Most tumors are deeply invasive.
The differential diagnosss includes metastasis from other sites, poorly differentiated squamous cell carcinoma, sarcoma, lymphoma and blue nevus.
The prognosis is poor with a 5-year survival rate ranging from 10-20%. It appears to be influenced by tumor size with lesions greater than 3 cm having a bad prognosis. Age, mitotic count, stage and location of the lesion do not influence survival.
Contributed by ED Manlucu, MD, H Dickson, CT (ASCP), L Mahood, MS, SCT (ASCP), ME Nath, MD