Podoplanin (D2-40) Expression in Mesenchymal and Clear Cell Chondrosarcoma
J Song, M Li, T Krausz, AG Montag. University of Chicago, Chicago, IL
Background: Cartilaginous tumors include a variety of benign and malignant entities which may present diagnostic challenges on histopathology. For example, mesenchymal chondrosarcoma (MC) can be hard to differentiate from other small blue cell tumors especially when it lacks chondroid matrix. Similarly, chondroblastoma (CB) and giant cell tumor (GCT) are both epiphyseal tumors with frequent giant cells which may have overlapping features. Podoplanin (D2-40), widely known as a lymphatic endothelium marker, is also expressed in cartilage, chondromas and some conventional chondrosarcomas. However, D2-40 expression in other cartilaginous tumors, including mesenchymal and clear cell chondrosarcoma (CCC), has not been investigated in the literature. SOX-9 is a master regulator for chondrogenesis, and has been suggested to be a useful diagnostic marker for mesenchymal chondrosarcoma. Our goal is to study the expression patterns of D2-40 and SOX-9, and assess their potential diagnostic values in several cartilaginous tumors.
Design: With IRB approval, 7 MC, 4 CCC, 12 CB, 11 GCT, and 12 aneurysmal bone cysts (ABC) were selected from University of Chicago pathology archive. Representative sections were stained for D2-40 and SOX-9 by standard immunohistochemistry. The staining intensity and percentage of positive cells were recorded, and graded as: diffuse (>50%), focal (1-50%), and negative. Normal cartilage and lymphatic vessels were excluded from evaluation.
Results: The results are summarized in Table 1. In positive MC cases, D2-40 and SOX-9 were strong, both in chondroid foci and in undifferentiated areas composed entirely of small blue cells. Interestingly, the single D2-40 negative MC had pleomorphic morphology and only focal SOX-9 staining. Both markers showed strong staining in CCC. CB had significantly stronger and more diffuse D2-40 and SOX-9 staining than GCT and ABC (all p values < 0.01, Mann Whitney U test). Most D2-40 positive GCT cases only had scattered cells (< 5% of total cells) highlighted by this marker.