Tenascin differentiates dermatofibroma from dermatofibrosarcoma protuberans: Comparison with CD34 and factor XIIIa

Differentiation of dermatofibroma (DF) from dermatofibrosarcoma protuberans (DFSP) carl be difficult. CD34 and Factor XIIIa have been used to differen tiate DF from DFSP. However, there is overlap and lack of specificity of th eir expression. Tenascin is an extracellular matrix glycoprotein that is in volved in embryogenesis, carcinogenesis, and wound healing. The aim of the study was to assess the role of tenascin in DF and DFSP and compare the res ults with those obtained with CD34 and Factor XIIIa. Immunohistochemical st aining was performed on 20 cases each of DFSP and DF, using antibodies to t enascin, CD34 and Factor XIIIa, and the streptavidin biotin technique. Posi tivity for all 3 antibodies was assessed within the tumors. Tenascin expres sion was also assessed at the dermal-epidermal junction. Strong tenascin po sitivity was noted at the dermal-epidermal junction overlying the lesion in 20 of 20 cases of DF (100%) and was negative over the lesion in 20 of 20 c ases DFSP (100%). Tenascin was noted within the lesion of 80% of both DF an d DFSP (16/20 cases). CD34 was strongly expressed in 16 of 20 (80%) DFSP an d 5 of 20 (25%;,) DF, whereas Factor XIIIa was strongly expressed in 19 of 20 (95%) DF and 3 of 15 (15%) DFSP. Although CD34 was expressed in 80% DFSP and Factor XIIIa in 95% of DF, there was overlap in their expression in th e 2 types of tumors. The increased expression of tenascin at the dermal-epi dermal overlying the lesion in DF but not in DFSP, differentiated these 2 t umors. In contrast, tenascin expression within the lesion did not different iate DF from DFSP. Copyright (C) 2001 by W.B. Saunders Company.