Four patients underwent intraoperative photodynamic therapy after surgery with meso-tetra(hydroxyphenyl)-chlorin (mTHPC-PDT) for diffuse malignant mesothelioma. Preliminary procedures were performed in two patients in order to establish the efficacy of mTHPC-PDT and to optimise its tumoricidal effect. The tumoricidal effect was related to the mTHPC dose, light dose and the time interval between...