The schema for histologic reporting of malignant melanoma outlined above is incomplete. A number of variables, including quantification of tumor cell pigmentation, description of solar degeneration in surrounding stroma, and extent of S-100 protein immunoreactivity by tumor cells, have not been addressed. In addition, it is likely that within the next several years, additional parameters, including those identified by the use of in situ genomic probes (Chapter 3), will become known to confer prognostic information when assessed histologically in biopsy material. Nonetheless, this approach represents a start, an attempt to achieve uniformity in histologic reporting of melanoma. It represents a three-tiered approach. First is the establishment of a malignant melanocytic lesion (malignant melanoma) and the assessment of the anatomic level and extent of invasion of the dermis, which correlates directly with metastatic potential (the vertical growth phase measured in millimeters). Subclassification of the radial growth phase is optional and, by convention, is also reported in this "above the line" portion of the diagnostic assessment. Second, a number of subsidiary diagnostic statements, usually in the form of notes or comments, are recommended. These include assessment of overlying epidermal ulceration, a description of the morphology and mitotic activity of the vertical growth phase nodule, an assessment of the presence or absence of vascular invasion and microscopic satellite formation, a description of the host mononuclear cell response and/or regression, and mention of associated pathology. Finally, an additional narrative statement may be included to describe such things as extent of S-100 immunoreactivity or to modify in a more descriptive manner the database provided above. Although this last category is neither crucial nor mandatory, it serves to add to a collective database from which future determinations concerning the prognostic significance of new histologic parameters may be formulated. Table 6.3 provides a sample report based on the above considerations. This method of histologic reporting is recommended because it includes important diagnostic information as well as parameters for prognosis. Although certain details of less impelling current significance are included, these are of potential future importance as a greater number of patients with malignant melanoma are followed prospectively for prolonged periods of time. These factors may also prove to be significant in the accumulation of a database for research.