The prognostic assessment and therapeutical strategies of canine MCT depend highly on the biological behavior of these tumors which is mainly correlated with histological grade. However, despite the presence of c-KIT mutations little is known about underlying molecular mechanisms for MCT development and malignant progression that could be responsible for the diverse malignant behavior of these tumors. Recently, the IL-2R α-subunit CD25 has been introduced as a marker to distinguish neoplastic from non-neoplastic human mast cells in SM patients which leads to the assumption that the IL-2R may have an impact on the development and tumor growth of neoplastic mast cell diseases. The aims of this project were therefore to evaluate CD25 as a possible tumor marker for canine MCT, to investigate the expression of the remaining subunits and the ligand of the IL-2R and to assess the usefulness of the IL-2R as a malignancy marker for canine MCT. Accordingly, the following hypotheses were tested in this work: First Hypothesis The IL-2R-α-subunit CD25 is expressed by canine cutaneous MCT and differentiates neoplastic from non-neoplastic canine cutaneous mast cells. Second Hypothesis The complete IL-2R and the ligand IL-2 are expressed by canine cutaneous MCT. The IL-2Ris increased in higher grade tumors and thus contributes to mast cell tumor proliferation.
