Microscopically, differentiation of DTE from morphea form/infiltrative BCC can be difficult because both show the islands and strands of basaloid cells embedded in a sclerotic stroma. A type II membrane-bound glycoprotein, FAP, which is part of the serine protease family, has been shown to heal wound granulation tissue. Expression of FAP was noted in peritumoral fibroblasts for all instances of morphea form/infiltrative BCC (25 of 25, 100%) but not in DTE (0 of 25, 0%). Here, FAP is linked to skin basal cell carcinoma.