Histopathological differentiation between desmoplastic trichoepithelioma (DTE) and morphealike basal cell carcinoma (BCC) is a difficult problem because of their similar morphological features. The matrix metalloproteinase stromelysin-3 (ST-3), which is expressed as a specific fibroblastic factor especially surrounding carcinoma cells, was studied in these both conditions of wholly different clinical outcome. Using formalin-fixed paraffin-embedded tissues, we found positive immunoreactivity for ST-3 in fibroblastic cells surrounding morphealike BCC cells in 34 (68%) of 50 cases, whereas the epithelial tumor cells themselves were negative. In none of the 12 cases of DTE did we observe expression of ST-3 in fibroblasts. We conclude that the antibody against ST-3 protein is an immunohistochemical marker to distinguish morphealike BCC from DTE.