Expression of stromelysin 3 in keratoacanthoma and squamous cell carcinoma

Stromelysin 3 (ST3) is a member of the metalloproteinase family, which is e xpressed in the skin during wound healing and in the stroma of basal cell c arcinoma. A high level of expression of ST3 has been observed in carcinomas of poor prognosis. In benign tumors, though, ST3 is not expressed or is at a low level. We have immunohistochemically studied the expression of ST3 i n 89 randomly selected cases of squamous cell carcinomas (SCCs), 104 of ker atoacanthomas (KA), and 23 cases of metastatic SCC. Stromelysin 3 was expre ssed only by fibroblasts surrounding the tumors and not by epithelial cells . The proportion of tumors positively stained was 22% of KA, 47% of randoml y selected SCC, and 70% of metastatic SCC. In areas of poorly demarcated ne oplastic cells, a reinforcement of the staining was observed in the stroma. The intensity and dispersion of staining were used to determine the level of expression. There were significantly more SCC in the groups of high expr ession levels, and both parameters were significantly higher in SCC than in KA. Expression of ST3 in benign tumors is unusual. Its expression in the t he stroma of keratoacanthomas can be related to the high tissue remodeling activity observed in these tumors. It also could be interpreted as in favor of the neoplastic nature of KA. Nevertheless, the level of expression was higher in SCC than in KA and seemed to be related to the prognosis of these tumors. These results correlate well with those obtained in boast cancers and in noncutaneous SCC.