A study of the thickness of uninvolved dermis beneath cutaneous malignant melanoma: the ratio of uninvolved dermis to tumour thickness (DT:TT) as a prognostic index.

The histological material from 147 patients treated for clinical stage I primary cutaneous malignant melanoma between 1968 and 1972 was reviewed. All patients had a minimum follow up of 10 years. Measurements were made of the thickness of uninvolved dermis (DT) deep to the tumour and the tumour thickness (TT) itself. The ratio of dermal thickness: tumour thickness (DT:TT) was correlated with clinical progress at follow-up and compared as a prognostic index with tumour thickness alone. The ratio DT:TT was found to be a useful prognostic guide, a value of greater than 2.0 proving to be a very favourable sign. It is suggested that this simple ratio should be routinely reported in all cases of primary cutaneous malignant melanoma to provide an additional index with a view to assessing its value as a prognostic guide.