SERUM S-100 PROTEIN - A POTENTIALLY USEFUL PROGNOSTIC MARKER IN CUTANEOUS MELANOMA

S-100, an acidic calcium-binding protein, is present within cells of n euroendocrine origin, Its value in the immunohistochemical diagnosis o f tumours of melanocytic origin is well established, More recently a p otential role has been proposed for the serum concentration of this pr otein as a marker of metastatic melanoma disease activity. In the pres ent study the concentration of serum S-100 protein was measured in 97 patients with histologically proven malignant melanoma who were attend ing a dermatology and/or oncology department for the follow-up of thei r disease. Serum S-100 was also measured in 48 control subjects withou t malignant melanoma. The clinical stage of the patients was classifie d according to the criteria of the American Joint Committee on Cancer into stages I-IV. The median (range) serum S-100 protein concentration was significantly higher in stage I (0.11 (0.1-0.21) mu g/L, P<0.001) , stage II (0.11 (0.05-0.22) mu g/L, P<0.001), stage III (0.24 (0.07-0 .41) mu g/L, P<0.0001) and stage IV (0.39 (0.06-15.0) mu g/L, P<0.0001 ) compared with the control group (0.1 (0.05-0.15) mu g/L). At a thres hold value of 0.2 mu g/L, the sensitivity and specificity for detectio n of advanced disease were 82% and 91%, respectively. Thus serum S-100 protein may be a valuable prognostic marker for malignant melanoma an d for monitoring therapy, Serum S-100 protein concentration was also c ompared with the Breslow thickness of the tumours. There was a signifi cant correlation between these variables (n=72, r(s)=0.32, P<0.01). Co mbining a serum S-100 threshold value of >0.22 mu g/L and a Breslow th ickness of >4 mm improved the sensitivity and specificity for the pres ence of secondary spread to 91% and 95%, respectively Therefore, a com bination of both baseline serum S-100 protein and Breslow thickness ma y provide a better indication of the prognosis at diagnosis.