[Malignant melanoma: depth of invasion and histologic typing]

In classifying a malignant melanoma Clark et al. (1969) have suggested histologic typing (lentigo maligna-melanoma, superficial spreading melanoma, nodular melanoma) as well as the determination of the depth of invasion. The experiences made so far need further confirmation through respective research in additional material. This applies to the frequency of histologic types of melanoma and the microstages and primarily to the prognostic significance. There appear to be correlations whether the depth of invasion or the type of melanoma is decisive for prognosis or whether both have to be considered.

Between 1967 and 1974 the depth of invasion and the type of melanoma were determined according to Clark et al. (1969) in 139 invasive malignant melanomas. This classification has been carried out routinely following the excision of the tumor since Jan 1st, 1973; in previously operated tumors it was carried out in retrospect without knowledge of the follow-up. Without exception multiple sections of several blocks were used. Uncorrected survival curves and survival rates were drawn up using the acturaial method. Results 1. Of 139 malignant melanomas 3 (2%) were found to be in microstage 2, 50 (36%) in microstage 3, 71 (51%) in microstage 4 and is (11%) in microstage 5. 2. The type of 2 melanomas could not be defined. Among the remaining invasive malignant melanomas 17 (12%) were lentigo maligna melanomas, 48 (35%) were superficial spreading melanomas and 72 (53%) nodular melanomas. 3. Of the 72 nodular melanomas 53 (74%) were found in microstage 4 or 5; of the 65 other melanomas (lentigo maligna melanomas or superficial spreading melanomas), however, only 34 (52%) p less than 0,001) were in this stage. 4. The uncorrected 5-year survival rate was 100% in microstage 2 and 3 and in tumours diameter of 0.76 mm or more, 55% in microstage 4 and 31% in microstage 5. 5. At equal depth of invasion there are no significant prognostic differences between the various types of melanomas.

It was possible to reproduce the type classification of melanomas as introduced by Clark et al. (1969) in our own material from 139 patients. Tumors of microstage 2 were less frequent in our material (2%) than in American and Australian series (17-28%). As far as the frequency of the types of melanoma and the correlation between the type of melanoma and depth of invasion are concerned, the Erlangen material does not show considerable deviation from the reports in the literature on the subject. Among tumors of equal depth of invasion the type of melanoma has little prognostic impact. The depth of invasion is decisive for the prognosis. It can be determined with little effort to a high degree of reliability.