Introduction: Melanoma of the skin shows a tendency to metastasize via lymph or blood secreting matrix metalloproteinases and cathepsins, which enable penetration through the dermis. Cathepsin K acts in cytoplasm of atypical melanocytes and completely cleaves internalized collagen.
Materials and methods: Expression of cathepsin K was analyzed immunohistochemically in 45 melanomas and correlated to morphological and clinical parameters.
Results: During six years follow up, 13 patients developed lymph node metastases and three of them distant metastases. Positive expression of cathepsin K was found in 19 cases. In univariate regression analysis histological type, pagetoid spread, mitotic activity and cathepsin K expression were significantly connected to metastases. Cathepsin K was significantly associated to histologic type, ulceration, pagetoid spread and mitotic rate. In multiple logistic regression adjusted to these variables, cathepsin K was an independent predictor in occurrence of metastases (P=0.015). Median to the occurrence of metastases was 40 months in patients with cathepsin K positive expression and 71 months in patients with cathepsin K negative expression (P<0.001).
Conclusions: In this preliminary study positive expression of cathepsin K in melanoma of the skin is associated with other unfavorable prognostic factors. We consider cathepsin K expression in primary tumor would significantly precipitate occurrence of metastases.