[512] Podoplanin (D2-40) Expression in Cutaneous Fibrohistiocytic Tumors: A Clinicopathologic and Immunohistochemical Study of 43 Cases.

Jose A Plaza, J Noelle Buonaccorsi, Saul Suster, Eduardo Zambrano. Medical College of Wisconsin, Milwaukee

Background: Podoplanin (D2-40) is widely used as a marker for lymphatic endothelial cells; however, it has also been found to be expressed in a number of non-vascular tumors. In normal human skin, podoplanin expression is confined to the basal cell layer of the epidermis, basal layer of sebaceous glands, and the basal layer of the outer root sheath of hair follicles; thus, expressed in many primary skin neoplasms. Lately, podoplanin expression has been found in some cutaneous fibrohistiocytic neoplasms but there is limited and conflicting data on this regard. We sought to analyze the expression of podoplanin in 43 cases of cutaneous fibrohistiocytic tumors including conventional and cellular dermatofibromas, to assess its potential diagnostic utility.
Design: A total of 43 fibrohistiocytic tumors form the basis of our study, including 16 cases of conventional dermatofibromas and 27 cases of cellular dermatofibromas. Available histologic material was reviewed, and 43 cases with unequivocal histologic features of either tumor were included in this study. Immunohistochemical studies were performed in selected formalin-fixed, paraffin-embedded blocks in all cases. The antibody employed was D2-40 (podoplanin) protein (1:200 dilution, DAKO, Carpinteria California). Appropriate positive and negative controls were run concurrently for the marker tested. Immunolabeling for podoplanin was scored as negative, focally positive or diffusely positive cytoplasmic staining. We defined negative as no reactivity, focally positive as staining in 1% to 25% of tumor cells and greater than 25% was defined as diffuse staining.
Results: Podoplanin immunoexpression was present in 15/27 cases of cellular dermatofibromas; 6 cases were diffusely positive (22.2%), 9 cases were focally positive (33.3%), and 12 cases were negative (44.4%). Podoplanin immunoexpression was present in 5/16 cases of conventional dermatofibromas; 1 case was diffusely positive (6.25%), 4 cases were focally positive (25%), and 11 cases were negative (68.75%).
Conclusions: In summary, the data generated in this study differs from other studies and suggest that podoplanin does not represent a sensitive marker in cutaneous fibrohistiocytic tumors. These results also suggest that podoplanin is more commonly expressed in cellular fibrohistiocytic lesions and thus may be used as a complementary stain to CD34, due to the difficult distinction between dermatofibrosarcoma protuberans and cellular dermatofibromas, especially in superficial biopsies.
Category: Dermatopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 122, Wednesday Afternoon


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