Melanoma in situ (MIS) adjacent to an invasive nodular melanoma (“SSM/NM”) and its metastases -DNA-cytophotometry, mitotic index, and anisokaryosis

Summary

Malignant melanomas of the superficial spreading type usually have an intraepidermal tumour component in their periphery which frequently displays the morphological features of a melanoma in situ (adjacent MIS). It is thus comparable to exclusively epidermal melanomas; melanoma in situ (MIS). Taking 10 superficial melanomas with a nodular component (“SSM/NM”) 31 adjacent MIS regions and 36 nodular melanoma components were analysed in serial tissue slides. Planimetric estimation of the nuclear areas was employed as a measure of anisokaryosis. DNA-Feulgen-cytophotometry was applied to obtain an objective variable in judging malignancy in the DNA-histographs (paraffin material). Furthermore we investigated 8 metastases of one of the malignant melanomas applying the methods described. A comparison of the epidermal with the invasive tumour components revealed an increase in the nuclear area which, however, decrease from the superior to the inferior nodular regions and which are further reduced in melanoma metastases. Anisokaryosis is evidently less in metastases compared with all primary melanomas. The nuclear DNA-content increases from the epidermal to the invasive tumour compartments and is lower in the inferior nodular regions when compared with the superior ones. No further significant differences are, however, established in the metastases. The coefficients of variability of the DNA-contents, being a potential indicator of DNA-heterogeneity reflect higher values in the epidermal tumour components compared with the nodular regions, decreasing from the superior to the inferior nodular parts of the tumour. All metastases have smaller values than the respective primary melanoma. In the DNA-histographs 75% of the intraepidermal tumour components have obvious signs of malignancy including tumour cell stem lines in 19% of the cases. 85% of the nodular regions investigated have clear signs of malignancy, 33% of which also have uneuploid stem lines. All metastases have obvious signs of malignancy and tumour cell stem lines in 50% of the cases observed. The following conclusions can be drawn from our findings: DNA-Feulgen-cytophotometry and nuclear planimetry are additional feasible methods for judging the epidermal component of a melanocytic lesion as malignant (adjacent melanoma in situ) on paraffin material. Furthermore these methods give different results in invasive nodular versus epidermal (in situ) melanoma components. Both the DNA-histographs and our immunohistochemical investigations (monoclonal antibodyP 3.58) indicate the malignant potential of adjacent MIS. Great DNA-heterogeneity both in primary melanomas and their metastases are of particular interest with regard to the possible predictibility of probability of metastases. This cannot be derived from our present findings.