1、Myoepithelioma of the Parotid Gland:CT Imaging findingsHuanhuan Su2012-02-06vME is a benign salivary gland tumor composed almost exclusively of sheets,islands,or cords of cells with myoepithelial differentiationvSpindle cells,plasmacytoid cells,epithelioid cells,clear cell patterns.vOther terms myoe
2、pithelial adenoma benign myoepithelial tumor IntroductionvBenign adenomas account for 65.5%of salivary gland tumors.vMEs were recognized as a histologically distinct entity in 1991 by the World Health Organization.IntroductionvMEs account for 1.5%of all of the tumors in the major and minor salivary
3、glands,and 40%arise in the parotid glands.vMinor salivary glands follow in frequency,especially in the palate(21%).IntroductionvThe age of patients with ME ranges from 9 to 85 years,with an average of 44 years and the peak age of occurrence in the third decade.vIt typically presents as a solitary,sl
4、owly growing,otherwise asymptomatic mass.vMEs are less prone to recur than pleomorphic adenomas.IntroductionCT imaging features and pathologyCT imaging features homogenous enhancement(Fig 1)inhomogeneous enhancement with enhancing nodules,the presence of cystic areas(Fig 2),slitlike-shaped area(Fig
5、3),and linear bands(Fig 4).smooth or lobulated contours located in the superficial lobe of the parotid gland,abutted the capsule of the gland CT imaging features and pathologyA 62-year-old woman with ME.A,Precontrast axial CT scan shows a round,well-defined mass(27.39 HU)in the superficial lobe of t
6、he right parotid gland abutting on the capsule of gland(arrow).B,Contrast-enhanced axial CT scan shows the mass(102.11 HU)with homogeneous strong enhancement(arrow).C,Microscopic examination(HE2)shows that the ME(M)is separated from the parotid gland and the surrounding soft tissues by a fibrous cap
7、sule(FC).The stroma is scanty.D,Microscopic examination(HE100)shows that the tumor is composed of the plasmacytoid and spindle cells.Relatively large vessels are seen in the tumor(arrows).CT imaging features and pathologyA 66-year-old woman with ME.A,Precontrast axial CT scan shows an indistinct mar
8、gin mass in the superficial lobe of the left parotid gland abutting on the capsule of the gland with calcification(arrow).B,Contrast-enhanced axial CT scan shows the mass with inhomogeneous enhancement.It contains a central enhancing nodule(small black arrow)and a nonenhancing peripheral cystic comp
9、onent(white arrow).C,Microscopic examination(HE10)shows the epithelioid nest(arrow)with a lot of vessels and a cystic component in the center(black asterisk).D,Microscopic examination(HE20)shows the inflamed cells(long arrows)and the tumor cells(short arrow).CT imaging features and pathology A 56-ye
10、ar-old woman with ME.A,Contrast-enhanced multiplanar reformatted coronal CT scan shows a well-defined mass in the tail of the right parotid gland with inhomogeneous enhancement(white arrow).Note the slitlike-shaped nonenhancing area (small black arrow).B,Microscopic examination(HE40)shows that there
11、 are hemorrhage(stars)and tumor cells(arrow)in the stroma.CT imaging features and pathologyA 54-year-old man with ME.A,Precontrast axial CT scan shows a well-defined mass with a lobulated margin in the superficial lobe of the right parotid gland abutted on the capsule of the gland(arrow).B,Contrast-
12、enhanced axial CT scan shows the mass with inhomogeneous enhancement.It contains enhancing nodules(arrows)and nonenhancing linear band(arrowheads).C,Microscopic examination(HE2)shows the stroma (black asterisks)and epithelioid nests(arrows)with a lot of vessels.D,Microscopic examination(HE100)shows
13、that the nest is composed of plasmacytoid.epithelial nest with plentiful blood vessels either collagenous or mucoid stromastroma surrounding hemorrhage nonenhancinglinear bandsslitlike-shapednonenhancing areaEnhancing nodulesCT imaging features and pathology high vascularityfaint enhancement no sign
14、ificant attenuation change betweenearly and delayed phase scanningVarious enhancement patternsMany biological factors influence the enhancement patterns of tumorsVarious enhancement patterns histological components of the tumorsvascularity histopathological cell typesspindle cell type with areas of
15、hyalinization plasmacytoid cell typewith myxoid stromafaint enhancementVarious enhancement patterns spindle cell type withfibrous stroma Cellular myoepitheliomas with fibrous stromahave more vascularity and enhancement than those with rich myxoid stroma.intenseenhancement Various enhancement pattern
16、svwell circumscribedvenhancing mass lesions with smooth or lobulated marginsvlocated chiefly in the superficial lobe and abutted on the capsule of the glandvenhancing nodulesvnonenhancing areas of linear bands,slitlike-shaped or of cystic configurationConclusionsDifferential diagnoses Pleomorphicade
17、nomas Relatively large cystic changes are more frequent in MEs than in pleomorphic adenomashappen in superficial and/or deep lobes of the parotid and not often abut the capsule of the glandlittle or no enhancement in the immediate postcontrast scan but manifest increased enhancement in the delayed s
18、can.Differential diagnosesWarthinstumors more common in elderly men than in women and can be multifocal and bilateral in 10%15%of patients.enhancing nodules formation and lobulated contours are more frequent in MEs than in Warthin tumorsenhancement in the immediate postcontrast scan.These features a
19、re similar to MEsMyoepitheliomas of the Soft PalateA 66-year-old man with ME.A.An early phase axial CT scan shows a well-demarcated soft palate tumor showing faint enhancement.B.A delayed axial CT scan shows heterogenous,nodular enhancement of the tumor.Myoepitheliomas of the Soft PalateA 65-year-old woman with ME.A.An early phase coronal CT scan shows an intensely enhancing soft palate tumor.B.A delayed axial CT scan shows persistent homogenous enhancement of the tumor.
