Malignant melanoma in situ

There is general agreement that there are lesions which should be diagnosed as malignant melanoma in situ. The biologic behavior of the intraepidermal component of superficial spreading melanoma (the radial growth phase) has been demonstrated to have significantly different properties than those of the cells in the vertical growth phase. The central controversies regarding malignant melanoma in situ relate to the criteria for diagnosing melanoma and whether there are atypical melanocytic lesions which are neither nevi nor melanoma. I propose that reliable and reproducible objective criteria for melanoma have not been developed; rather, dermatopathologists use differing subjective criteria which result in diagnostic agreement in the vast majority of lesions. The controversy is over those lesions which are classified as melanoma by one set of criteria and not by others. I am also a proponent of the diagnosis of atypical melanocytic lesions, and have suggested an analogy to keratinocytic lesions in which this concept is well established. Studies of the sensitivity and specificity of the correlation between clinical and histologic features and the biologic behavior of melanocytic lesions are necessary to resolve these issues.