Cathepsin K is a protease that is involved in bone resorption, and is highly expressed in osteoclast. Its expression has also been demonstrated in normal skin and lung fibroblasts. In neoplastic tissue, Cathepsin K has been reported to be expressed in most mesenchymal tumors, but only rarely in carcinomas.
Cathepsin K is positive in the majority of translocation renal cell carcinomas (seven of the Alpha-TFEB gene fusion translocation), and in all 5 of the most common TFE3-positive renal cell carcinomas bearing the t(X;1)(p11.2;q21) translocation. This assay is intended for the identification of these renal cell carcinomas.
Published data suggest that TFE3 expression leads to cathepsin K expression. While less sensitive than TFE3, cathepsin K has also been demonstrated in a subset of renal cell carcinomas showing a different translocation, t(6;11). While these latter translocations cannot be identified with antibodies to TFE3, they may account for the apparent reduced specificity of cathepsin K in our study, as the TFE3-negative, Cathepsin K-positive renal cell carcinomas may well correspond to these t(6;11) translocation renal cell carcinomas.
Final determination of translocation status in renal cell carcinomas may require FISH or PCR studies.
Subcellular Localization: Cytoplasmic
CPT Code(s): 88342 or 88341 (reference only; CPTs may vary)
Turnaround Time: Within 1-2 business days of receipt
Schedule: Monday - Friday
• Formalin-fixed, paraffin-embedded (FFPE) tissue block or cell block - OR -
• 1 unstained slide for each test requested plus 3-4 additional unstained slides cut at 4µm