Clinical and pathological correlation of malignant melanoma

We have attempted to review virtually all forms of cutaneous and mucocutaneous melanomas. Superficial spreading, lentigo maligna and nodular melanomas have been more thoroughly investigated and documented in previous studies. Lentigo maligna melanoma appears to have a longer duration and better prognosis than SSM or NM. The overall prognosis probably correlates better with the anatomic level and thickness of invasion than with type (Clark et al. 1975, Breslow 1970, 1975). It appears that certain pitfalls exist in either method of assessing prognosis, and it is recommended that both methods be applied in evaluating a malignant melanocytic lesion when feasible. With regard to in situ melanoma or Level I melanoma, it is our experience that such lesions can achieve a 100% cure rate when completely excised. Hence, we prefer to call such lesions severely atypical melanocytic hyperplasia, and thus avoid labeling these patients with a malignant diagnosis. The most difficult histologic challenge in diagnosing a lesion of malignant melanoma is the Spitz nevus. The pathologist should never be biased by the age of the patient, for a serious mistake can arise. We have seen a case of nodular melanoma in a 13-year-old girl diagnosed as Spitz nevus only to be followed by a lymph node metastasis years later. Other examples of histologic differential diagnoses of malignant melanomas include, for example, halo nevus, soft tissue sarcoma, squamous cell carcinoma with spindle cell proliferation, Paget's disease of metastatic carcinoma, (for example, from the breast). Therefore, the approach to the diagnosis of malignant melanoma necessitates an evaluation of both clinical and pathological features. Histologic study must encompass both the pattern of growth and cellular cytologic detail for successful interpretation.