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Pathologic changes were observed in S180 fibrosarcoma transplanted in white mice of Kunming line and in human hepatocellular carcinoma transplanted in balb/c nu/nu nude mice after photodynamic therapy (PDT) with sulfonated aluminum phthalocyanine (AlSPC). The experimental tumors in mice were chosen with diameters in the range of 0.5 - 0.8 cm. A dose of 10 mg/kg AlSPC was given (iv). The dose of light (600 - 750 nm) was 180 J/cm2. Degeneration of tumor cells, microvascular hyperemia, stroma edema, and hemorrhage were found soon after PDT under the microscope and the hyperemia and hemorrhage in hepatocellular carcinoma seems more obvious than in S180 sarcoma. Heave hyperemia and hemorrhage can not always be seen in the degenerative and necrotic area in S180 sarcoma. With transmission electron microscopic technique, the most significant early changes are apparent degeneration of the mitochondria, slight dilation of rough endoplasmic reticula, a little increase of lysosmes (both in tumor cells and in endathelia), collagen fiber degeneration in the subendothelial zone of the capillary wall and in other connective collagen fibers, and slight edema in intercellular space and in the interstitial tissue surrounding capillaries immediately after completion of 30 min PDT. Additionally, the results were discussed in combination with our other study of histochemistry on seven kinds of tissue enzymes in hepatocellular carcinoma which shows the activities of these enzymes reduced to be inconsiderable from within 30 min to within 6 h after AlSPC-PDT, in which the activity of SDHase reduced most quickly. The pathologic study suggested the cellular membrane system, especially the mitochondria, was probably one of the main reaction targets of AlSPC-PDT though what is the most important primary target (the tumor cell's and endothelium's mitochondria or subendothelial zone, or some other structure) further study is required to answer.
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