Mucous retention cyst (MRC) is not uncommon in the pathology of maxillary sinus, which should be differentiallydiagnosed from chronic maxillary sinusitis. The main stream of diagnosis usually depends on the clinical symptoms andradiological findings. Thus it was sometimes puzzling to confirm the histological features of mucous retention phenomenonin the antral mucosa, when the specimen was from a limited portion or much degenerated by inflammatoryreaction. This study aims to define the histopathological features of MRC through reevaluation of MRCs (n=19) andmaxillary sinusitis (n=65) diagnosed previously. The present study classified three types of MRC, i.e., an extravasationtype, a luminal retention type, and a mixed type of MRC. The extravasation type MRC showed clear pseudocyst cavityunder sinus mucosa with infiltration of foamy macrophage, and the luminal retention type MRC showed mucous retentionin the luminal cavity of maxillary sinus accompanied with inflammatory reaction, and the mixed type MRCshowed the both features of extravasation and luminal retention type MRCs. Resultantly, among nineteen cases of MRConly three cases belonged to the extravasation type MRC, eleven cases belonged to luminal retention type MRC, andthree cases belonged to mixed type MRC, while two cases were turned out to be postoperative residual cysts of maxillarysinus. The MRCs examined in this study showed different pathological features from ordinary maxillary sinusitis,exhibiting the typical mucin retention phenomenon of extravasation type or luminal retention type with relatively mildinflammatory reaction with infiltration of mucin-pooled macrophages. However, the luminal retention type MRC waspredominant among the MRCs (11/17, 64.7%) and each of the extravasation and mixed type MRCs was only three casesout of 17 MRCs (17.6%). The extravasation type MRC characteristically produces a pseudocyst by the overexpressions ofmatrix metalloprotease-3 (MMP-3) and connective tissue growth factor (CTGF). Because not only the pathogeneticmechanism but also the prognosis of MRC is different from chronic maxillary sinusitis, we suggest that the MRC ofmaxillary sinus should be classified into extravasation, luminal retention, and mixed types in the histological observationsin addition to the clinical and radiological informations.

 PDT is an established cancer treatment modality. This can be attributed to the attractive basic concept of PDT;Combination of two therapeutic agents, a photosensitizing drug and light, which are relatively harmless by themselvesbut when combined, cause more or less selective tumor destruction. Hematoporphyrin-derived photosensitizers areknown to be stable and highly efficient. In this study, we conducted a series of experiments to develop light-inducedanticancer drugs against oral cancer cells. We tested the cytotoxicity of photodin by MTT assay and observed celldeath pattern (apoptosis or necrosis) by hoechst 33342 and propidium iodide staining methods after PDT. IC50 value ofphotodin was 0.65 ug/ml. At higher doses of photodin ( > 7.8 ug/ml), cancer cells died exclusively from necrosis afterPDT. By contrast, at IC50 value, photodin induced cancer cell to undergo apoptotic cell death. The induction begins approximately6 hours after PDT. We investigated intracellular localization of photodin by oral cancer cell via confocallaser scanning microscopy. Oral cancer cells dual-stained with photodin and organelle-specific fluorescence probes(Mitotracker, Lysotracker, ER-Tracker) revealed that an intracellular fluorescence distribution was restricted to cytoplasmiccompartments with no detectable fluorescence in the nucleus. Confocal images of cells containing photodinwere overlapped with the mitochondria-specific fluorescence probe images of the same cells. These results demonstratedthat photodin may play the role of a photosensitizer for oral squamous cancer cells without swelling andinflammation. Therefore, photodin-based PDT is a suitable treatment for oral cavity carcinoma patients.