Aims: To immunohistochemically investigate the expression of cathepsin B and cathepsin L in various lung cancer cell types in association with the patients' prognosis.
Materials and methods: Histological slides obtained from formalin-fixed, paraffin-embedded tissue of 120 potentially curative resected lung cancer specimens (20 cases of each of the following cell types: squamous cell, adeno, large cell anaplastic, small cell anaplastic, intrapulmonary metastases, mesotheliomas) were quantitatively immunohistochemically analysed with an automated image analysing system and correlated with the patients' prognosis and the tumour proliferation rate measured by the expression of Ki-67.
Results: The expression of cathepsin B was most frequently present in large cell anaplastic carcinomas and missing in small cell carcinomas. That of cathepsin L was less frequently seen, and mainly expressed in macrophages and adenocarcinoma tumour cells. The structural heterogeneity of cathepsin B expression measured by syntactic structure analysis was greater than that of cathepsin L. The expression of cathepsin B is of prognostic significance in non-small cell lung cancer, and ranges directly after the pN and pT stages in multivariate statistical analysis.
Conclusion: In concordance with the literature, the expression of cathepsin B in non-small cell lung cancer should be considered as a significant prognostic parameter in contrast to that of cathepsin L, which is not related to the patients' outcome at a statistically significant level.