The expression of cathepsins in osteoclast-like giant cells of an anaplastic thyroid carcinoma with tracheal perforation

Anaplastic carcinoma of the thyroid gland (ACT) is a rapidly growing neopla sm with a very poor prognosis. In this study, we examined an ACT with osteo clast-like giant cells expressing matrix - degrading cysteine proteinases a nd their endogeneous inhibitor cystatin C. Bronchoscopic evaluation of a 50 -year-old man suffering from hoarseness, dysphagia, and dyspnea revealed an irregular tumor mass infiltrating into the trachea and the cricothyroid li gament region. On histological examination, a necrotizing undifferentiated anaplastic carcinoma with osteoclast-like giant cells was detected. An immu nohistochemical study of the tumor tissue was performed using a panel of 15 antibodies, including double labeling techniques. Most of the osteoclast-l ike multinucleated giant cells (MGC) expressed CD68 and cathepsin K. Coloca lization of cathepsin B and its endogenous inhibitor cystatin C occurred in the majority of MGC. Mononuclear cells (MC) were positive for cathepsin B, cystatin C, and CD 68, but only faintly for cathepsin K. Expression of cathepsins B and K in the MGC of the ACT might contribute to the invasive behavior of this tumor, thus promoting metastatic ability and destruction of the cartilagenous trachea.