Immunohistochemical evaluation of the small and large proteoglycans in pleomorphic adenoma of salivary glands

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Abstract
This study investigated the immunolocalization of small and large proteoglycans (PGs), including decorin, biglycan, PG‐M/versican and aggrecan, in salivary pleomorphic adenoma (PA) using monoclonal and polyclonal antibodies. In addition, a polyclonal antibody, A0082, recognizing blood vessels was also used to help identify truly mesenchymal tissues in PA. Decorin reactivity was detected only in tumor capsule and interstitial tissue of non‐neoplastic salivary gland, but not in the tumor tissue. Biglycan was frequently revealed throughout the matrix of small chondroid regions and in the peripheral portion of larger chondroid regions. PG‐M/versican was mainly localized to the truly mesenchymal tissues in PA and the innermost portion of tumor capsule. On the contrary, aggrecan was extensively expressed in the non‐luminal epithelial areas as well as in the myxoid and chondroid areas, but not in the truly mesenchymal tissues. These findings suggest that aggrecan is the most widely distributed PG in PA and may be produced mainly by non‐luminal tumor cells. The absence of aggrecan from the truly mesenchymal tissues argues against its origin from this source. Both aggrecan and biglycan may play important roles in the chondroid differentiation and morphogenesis of PA.