Clinical and pathologic diagnosis, staging and prognostic factors of melanoma and management of primary disease

Abstract

To increase detection of melanoma, medical practitioners and the general public should know the signs of early invasive melanoma. The Scottish Melanoma Group recently presented a revised checklist of the major and minor signs. The validity of the reported clinical and histopathologic criteria for the dysplastic nevus, a precursor to cutaneous melanoma, is not fully established. However, expert pathologists agreed on the use of major and minor criteria. The differential diagnosis between spindle-epitheloid cell nevi and melanoma remains problematic, because the former lesions often show cellular atypia. Other lesions that can cause considerable diagnostic difficulties are melanoma in situ and minimal-deviation melanoma. Immunohistochemical studies of human melanocytic lesions have contributed to the diagnosis of poorly differentiated tumors but, so far, have not helped in the discrimination among benign, premalignant, and malignant lesions. They have provided additional prognostic information in cases of primary melanoma and locoregional melanoma metastasis. Quality control of antibody reagents continues to be a problem. Microstaging of primary melanoma using Breslow depth and Clark's level of invasion may be subject to considerable intra- and interobserver variation. To improve the accuracy of the measurements, using a vernier scale is recommended. The type of melanoma is relevant in considering clinicopathologic prognostic factors. Acral melanoma (for example, that arise from glabrous skin) has been reported to carry a grave prognosis. Polypoid melanoma may have a less unfavorable outlook than previously thought. DNA cytophotometry provides prognostic information in case of primary melanoma but loses significance when stratified for tumor thickness. In patients with lymph node-positive melanoma, however, DNA ploidy analysis appears to yield additional prognostic information. In the management of primary disease, the width of the surgical excision and whether to approach the regional lymph nodes remain the main issues. A multicenter study conducted by the World Health Organization Melanoma Programme has found that a "narrow" excision is a safe procedure for primary melanomas not thicker than 1 mm. Several investigators underline the need for continued annual follow-up for all melanoma patients; recurrence may occur late. Currently, elective lymph node dissection is not recommended in the management of "thick" primary melanoma. Because data from randomized trials conducted in patients with a tumor of intermediate thickness are not yet available, only guidelines on management offered by experienced surgeons can be given. Patients with the dysplastic nevus syndrome should be closely followed so that melanomas can be diagnosed as early as possible.