The pathology of malignant melanoma.

It is clear that much of what has been taught over the years concerning the pathology of melanoma may have little validity. Melanoma is viewed simply as a malignant neoplasm comprised initially of a proliferation of atypical melanocytes within the surface epithelium (epidermis). It has many features in common, regardless of anatomic site. It spreads within the epidermis first for months, possibly years or even for decades. At this stage (melanoma in situ) it is wholly curable if completely surgically excised. What determines how long a given melanoma remains in situ is not clear. It is probably a combination of factors, including host response to the neoplasm; physical barriers to growth and metastasis (perhaps solar damage); chemical or humoral growth factors or inhibitors (perhaps genetically determined); and other as yet undiscovered factors. Once a given neoplasm penetrates into the subjacent dermis, there are whole ranges of ill-defined events that act on its ability to continue to grow and develop the competence for metastasis (growth factors and inhibitors, neoangiogenesis factors and inhibitors, host immune responses, and so forth). Let us throw out all of our prejudices that may have developed or nurtured over the years. There is much to learn about the pathobiology of melanoma. Clinicians should keep their minds open to new concepts and try to separate what makes sense from that which does not.