title: Mechanism of intramedullary high intensity area on T2-weighted magnetic resonance imaging in osteoid osteoma: a possible role of COX-2 expression.
abstract: To study the mechanism and pathophysiology of the development of intramedullary high intensity areas on T2-weighted magnetic resonance images (MRI) in cases of osteoid osteoma, we examined the expression of cyclooxygenase-2 (COX-2) in the nidus and surrounding bone tissues. In all six cases showing a marked intramedullary high intensity area adjacent to the nidus before surgery, neoplastic osteoblasts inside the nidus showed strong and diffuse COX-2 immunoreactivity. On the other hand, the osteoblasts rimming the surrounding reactive bone were COX-2 negative. In two cases examined by reverse transcription-polymerase chain reaction (RT-PCR), COX-2 mRNA was detected in abundance in the nidus. Histologically, vascular dilatation together with intramedullary edema was observed in all cases, which was probably reflected as a high intensity area on T2-weighted MRI. From our study, a high level of COX-2 expression in neoplastic osteoblasts in the nidus of osteoid osteomas may cause the secondary changes depicted by MRI.
authors.affiliation: Department of Orthopedic Surgery, Kagawa Medical University, Japan. yojin@kms.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: T
authors.initials: T
authors.lastname: Hasegawa
authors.forename: S
authors.initials: S
authors.lastname: Oka
authors.forename: C
authors.initials: C
authors.lastname: Sato
authors.forename: N
authors.initials: N
authors.lastname: Arima
authors.forename: H
authors.initials: H
authors.lastname: Norimatsu
mesh_terms: D000293:Adolescent; D000328:Adult; D001859:Bone Neoplasms / Q000201:enzymology* / Q000473:pathology / Q000601:surgery; D002648:Child; D051546:Cyclooxygenase 2; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D008279:Magnetic Resonance Imaging; D008297:Male; D008565:Membrane Proteins; D010006:Osteoblasts / Q000201:enzymology / Q000473:pathology; D010017:Osteoma, Osteoid / Q000201:enzymology* / Q000473:pathology / Q000601:surgery; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D007527:Isoenzymes; D008565:Membrane Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases