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AJR :1 69 , O c to b e r 1997 985

M ed ias tin a l M a tu re Te ra tom a:Im ag ing Fea tu res

K ath le en H . M oe lle r1 2M e li ss a L . R o sa d o- de -C h ris te n so n 23P hilip A . T em p le to n4

OBJECT I VE . The purp o se o f th is s tudy w as to charac te rize the cross-sec tio na l im ag ingfea tu res o f m ed ias tina l m atu re te ra tom as .

MATER IA LS AND METHODS . S ix ty -s ix c ase s o f m ed ias tina l m a tu re te ra tom a w erere trospec tive ly rev iew ed , no ting c lin ica l, rad io log ic , su rg ica l, an d p atho lo g ic find ings . T hepa tien t po pu la tio n cons is ted of 38 fem ales and 28 m ales w ho w ere I w eek to 67 years o ld(m ean age , 2 3 years 10 m on th s).

RESULTS . For ty -s ix pa tien ts p resen ted w ith sym ptom s, p redom in an tly ches t p ain , d ysp-nea , and co ugh . Tw en ty pa tien ts w ere asym ptom atic . F ifty -four tum ors w ere found in the an-te no r m ed ia stin um , tw o in the p oste rio r m ed iastinum , one in the m idd le m ed iastiiium , an dnin e in m u ltip le com par tm ents . C T stud ies (ii = 66 ) show ed m asses o f he te rogeneou s a ttenua-tion w ith v ary ing com b ina tion s o f soft tis sue , flu id . fa t, a nd c alcium . S oft-tis sue at ten uat ionwas observed in 6 6 tum ors ( 100% ), flu id in 58 tum ors (88% ). fat in 50 tum ors (76% ), and ca l-cifica tio n in 35 tumors ( 53%) . The m ost frequ en t com bina tio n of attenua tions w as soft tis sue ,f lu id , fa t, and calc ium , w hich w as no ted in 26 masses (39% ). T he com b in a tion o f so ft tis sue ,flu id , an d fa t w as seen in 16 tum ors (24% ); and the com bina tion of so ft tis su e an d flu id w asseen in 10 tum ors ( 15%) . F at- flu id leve ls w ere seen in seven m asses (1 1% ).

CONCLUS ION . M edias tina l m atu re teratom a ty p ically m an ifes ts on CT as a h ete rog e-neous an te rio r m ed ias tin a l m ass co n tain in g soft-tissue , flu id , fa t, o r ca lc ium atten ua tio n , o rany com bina tion of the fou r. F lu id -con ta in in g cys tic a reas, fa t, and ca lc ifica tio n o ccur fre -quen tly . C ys tic lesion s w itho u t fat o r ca lc ium w ere seen in 15% of tum ors. Fa t-flu id lev els ,cons id ered h igh ly sp ec ific fo r the d iagno sis o f m ed ias tin al m atu re te ra tom a, a re uncomm on .CT is the im ag ing techn iqu e of cho ice in th e eva lua tion of these les ions.

R e ce i ve d F e br u ar y 1 4 , 19 9 7; a cc e pt e d a f te rr e v is i onA pril 1 5, 1 99 7.T he o pin io ns a nd a ss ert io ns co nta in ed h ere in a re th ep r iva te v ie ws o f t he au tho rs an d a re n ot to b e con strued aso ffic ia l o r a s rep resen t ing the v ie ws o f the D epa rtm en ts o fth e Navy , A ir F orc e, o r D efe ns e.P r es e nt e d a t t h e a n n ua l m e et i ng o f t he A m er i ca n R o en t ge nR ay S oc ie ty ,W as hi ng to n , D C, M ay 1 99 5.1 D e pa r tm e n t o f R a d i ol o gy , Na t io n a l N av a l M e di c al C e nt e r,8 90 1 W is co n si n A ve ., B et h es da , M D 2 08 89 -5 00 0 .2 De pa rtm en t o f R ad io log y an d N uc lea r M ed ic ine , th eU nifo rm ed S erv ice s U niv ers ity o f th e H ea lth S cie nce s,B eth esd a, M D 2 08 14 .3 D ep a r tm e nt o f R a d i o lo g ic P a t h ol o gy , A r me d F o r ce sI n s t i tu t e f P a t h o l o g y , Wa s h i n gt o n . D C 2 0 3 0 6 -6 0 0 0 .A dd re ss c orre sp on de nc e to M . L R os ad o-d e-C hri ste ns on .4 D e p a r tm e n t o f R a d i o l o g y ,U n i v e r si t yo f M a r y l a n d M e d i c alS ys te m , B alt im o re , M D 2 12 01 -1 59 5.AJ R 1997 :169 :985 -9900361-803X197 /1694-985 A me ri ca n R oe nt ge n R ay S oc ie ty

M ed ia stin al m a ture teratom a is ara re prim ary ge rm ce ll neop lasmcom posed of w e ll-d iffe ren tia ted

tis su es derived from m ore th an one o f th eth ree em bryon ic germ cell layers [1 ]. C ross -sec tio na l im ag ing us ing C T , M R im aging , andsonography a llow s iden tification of d iffe ren telem ents w ith in these tum ors in clu d in g sof tt issue, flu id , fa t, a nd calcium . A lth ou gh theim ag ing fea tu res o f m ed iastina l m atu re te ra -tom a h av e been desc ribed in sm all se ries andc ase repo rts, to ou r k now ledg e n o larg e ser iesd efin ing th e im ag in g charac te ristic s o f thesetum ors and the re la tiv e frequency of d iffe ren ttis sue e lem en ts has been pub lished .

M a te ria ls and M e thodsA retrospec tive rev iew of all m ediastinal m a-

tu re tera to rn as do cum en ted in th e com pute r-ba sed

tile s of the d epa rtm en t o f R ad io log ic P ath o lo gy o fthe A rm ed Forces In sti tu te of P ath o lo gy , co llec tedbetw een 1942 and 1995 . y ie lded 1 46 ca ses . S ix ty -six c ase s w ere ev alu ate d rad io log ically w ith c ros s-sec tio nal im ag ing s tud ies inclu d in g C T and w e reselected fo r re v iew on that bas is. T he c lin ical h is-to r ies, p ath o lo g ic fin d in gs, a nd rad io log ic im agesw e re retrospec tiv ely rev iew ed by th ree rad io lo-g is ts an d c lass ifie d b y co nsensus.

H isto r ies w ere ana lyzed . n o tin g age . sex , andcom plain ts at p re sen tat ion . Th e surg ery and pa-tho log y repo rts w ere rev iew ed to determ ine les ionlocation, size , an d gross featu re s. Th e d iagn osis o fm ature teratom a w as pa tho log ica lly co nfirm ed ineve ry ca se. C ase s o f im m atu re terato rna , m alig -11am tera tom a, o r te rato rn a w ith a sso cia ted e le-vate d se ro lo g ic m arkers (a- fe topro te in and hum ancho rio n ic go nad otrop in) cons iste n t w ith in trins icm align an t e lem ents w ere exc lud ed .

Ches t rad iograph s an d thorac ic CT scans w ererev iew ed in every case. R ad io graph ic fea tu res

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D eca de s o f L ife (ye ars )

F ig . 2 -9 -yea r-o ld g irl w ho had cou gh and rig h t sh ou lde r pa in . C on tra s t-enh an ce d CTscan (m ed ias tina l w ind ow se ttin g) re vea ls la rg e he te ro ge ne ou s a nte rio r m ed ia stin alm ass th a t c on ta ins th in so ft- tiss ue se p ta (curved ar r ow) , w h ic h c om p a rt m en ta li zeflu id )f) a nd fa t-con ta in in g a rea s (as ter isk ) . N ote f loc cu len t ca lc ifica t ion , m ass e ffec ton m ed ias tin um , an d a te lec ta sis (o r c on so lida tio n) o f ad jacen t lu ng (o pe n a rr ow ).

Moe lle r e t a l.

98 6 A JR :1 69 , O cto be r 19 97

14128

6

Z 2

F ig . 1 .-G raph show s oc cu r ren ce o f m ed ia s tin a l m atu re te ra tom a by decades o flifein66 pa t ien t s .

su ch as size , lo ca tion . bo rde r ch ara cter istics, p res-en ce o f ca lcifica tio n . fa t-flu id leve ls, and o ther as-so cia ted f ind ing s w ere no ted . L ocatio n w ith in theiiied iastinum was de term in ed using th e Fe lso nme th o d 121 . C hest CT sc ans w ere ob tained u sin g avar ie ty of scan ners w ith var iab le tech n iq ues ofco n trast m a teria l a dm in is tra tion . In 38 ca ses . sc an swere enhanced : in 14 cases, scans w ere unen-han ced : and in 1 4 ca ses . bo th un enh an ced and en-hanced scan s w e re inc lud ed . C T scan s w erean a ly zed n o ting bo rder characte ris tic s , location ,tissue elem ents in the tum ors (soft-tis sue , flu id ,fa t. and ca lc ium attenu ation ) . and the ir frequ en cyof o ccu rrence . Lo ca tion on the C T scan w as estab-l ish ed by us ing the m odif ied trad i tion al m ethod[21 . Che st w all m uscle . sub cu taneous fat , a nd os -seo us struc ture s w ere used a s in ternal refe ren cestandards fo r so ft t issu e, fa t . an d calcium . resp ec -tive ly . S oft-tissue e lem en ts w ere ca tegor ized asnodular . s ep tate , o r p erip he ral a nd th ic kne ss w asa sse ssed . N onenhancin g are as o f in term ed iate a t-tenu atio n b etw een soft tissue and fat w ere class i-fled as flu id . R eg ion of in te res t m easurem en tsw ere n oted if ava ilab le . A reas of ca lcif ica tionw er e c ate go riz ed as linea r, cu rv i lin ear. p unc tate .o r floccu len t. A ddit ion al find ing s in clud ing m assef fect and assoc ia ted pu lm on ary . p leu ra l, or p en-card ial abn orm alitie s w ere n o ted .

Fourteen cases w ere ad d ition a lly eva lu a tedw ith M R im agin g (a = 8 ) o r s on og ra ph y (a = 6) .The eigh t M R im agin g sequ ences inc lud ed atle ast T I- and T2 -w eigh ted im age s. P ro ton d en-s ity -w e igh ted im age s w e re avai lab le in th re ecases. A ll m asses eva lua ted w ith M R im ag ingw ere im aged in m u ltip le p la nes . typ ica lly ax ialan d coronal. Si gnal intensitie s compatibl e withfa t . sof t t issue, flu id , o r any com binat ion o f th eth re e w ith in the le sion s w ere no ted . Sonog ram sw er e e va lu ate d fo r cys tic . so lid , o r com plex e le -m en ts and fo r areas of calcificat ion .

Resu l t sClin ica l Presen ta t ion

P atien ts inc luded 38 fem ales and 28 m ale sw ho were 1 w eek to 67 years o ld (m ean age , 23years 10 m onths ; m ed ian ag e. 23 years). F ifty -five pa tien ts (8 3% ) w ere younger than 40 yearso ld at the tim e o f p resen ta tion (F ig . I ). For ty -six pa tien ts (70% ) h ad sym ptom s inc lud in gchest pa in (ii = 32 ), d yspn ea (a = 13 ), c ou gh(ii = 10 ). upper resp ira to ry in fec tion (a =5) , fever (,i = 3 ), co nst itu t ion al sym p tom s(I = 2), w heezing or s tn id or (,i = 2 ). p alp it a-t ions (ii = 1 ), and hem optys is (a = 1 ). Nine teenpa tien ts (2 9% ) repo rted m u ltip le sym p tom s.Tw en ty pa tien ts (30% ) w ere asym ptom atic .

Patho log ic F ind ingsP atho logy reports descr ib in g the resec ted

gross sp ec im ens w ere ava ilab le in a ll 66cases. T um or s ize w as reported fo r 6 3 tu -m o rs and ran ged from 5 to 17 .5 cm (m eans ize, 1 0 .3 cm ) in lon gest d im ens ion . M acro -sco p ic cysts w e re iden tif ied in 6 4 tum o rs(97% ) and con tained a w id e ran ge of f lu idtypes. Cheesy , fa t ty , o r f ib rous tissue w a sno ted in 39 les io ns ( 59%) . h air w as n oted in34 les io ns (52% ). an d m inera lized e lem en tsco nsis ting of bon e (ii = 7) or tee th (a = 4)w ere n oted in 1 1 les ion s (1 7% ).

R ad io gra ph ic F in di ng sC hest rad iograp hs revea led a m edia .s tina l ab -

norm ali ty in a ll 66 p a tien ts. T he abnorm alityw as charac te rized as a m edia .stin al m ass in 61pa tien ts (9 2% ), d iffuse m ed iastina l w id en in g intw o p atien ts (3% ), a m ed ias tina l m ass part ia l ly

obscured by ad jacen t pu lm onary p aren chym alcon so lida tio n in tw o p atien ts (3% ). and card io-m egaly in one pa tien t (2% ). R ad iog raph ic ev i-dence of ca lcifica tio n w as seen in 14 m asses(2 1 C/c) an d w as cla ssified a s am orp hou s (a = 6) ,a s p er ip h er al an d curv i l inear (a = 5 ), o r as rep re -sen ting bon e (a = 2) o n te eth (a = 2). O ne m asshad bo th bon e an d teeth . A rea s of re la tive rad io-luc ency su gg esting fat w ere no ted w ith in fourmasses (6 c ) an d corre la ted w ith a reas o f fa t a t-tenua t ion on the corresp tJnd ing CT scans . O nlyon e m ass (2C /) had a v isib le fa t- flu id leve l.

T umo r marg ins were sha rp ly outlinedag ain st th e ad ja cen t lu ng in 5 8 les ion s (8 8% ).Thir ty - three iia sse s (5 0% ) h ad a lobu la tedcon tou r and 25 m asses (38% ) had a sm ooth ,sp herical n iarg in . E igh t lesions ( 1 2% ) had ill-de f ined (a = 6) o r in de te rm in ate (a = 2) bor-dens . F ifty -fo ur tum ors (82% ) w ere u n ila te ra land I 2 tum ors ( I 8% ) crossed the m id line .T hirty -f ive m asses (53% ) w ere predom i-nan tly le ft-s ided : 2 6 m asses (3 9C% ) w ere p re-dom in an tly righ t-sid ed : an d fiv e m asses (8% )were loca ted in the m id line . T he m asses w ereco nfin ed to a sin g le m ed ias tina l com pa rtm entin 57 p atie n ts (86% ) w ith 54 tera tom as lo-cated in th e an terio r, tw o in the po ste rio r , andon e in the m iddle m ediast inum . M ult ip le m e -d i as t in a l c o mp a rt m en t s were af fec ted in n inepat ien ts (1 4c/d . F ive le sio ns (8% ) w e re as so-cia ted w ith air spa ce op acity on co nso lid ationin th e ad ja cen t lu ng .

CT Fea tu r esF ifty -n ine m asses ( 8 9 %) h ad w el l- de fi ne d

m arg in s ag a in st the ad jacen t lung on C T scan s

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F ig . 3 .-45 -ye a r -o ld w om an w ho had che s t d iscom fo rt a n d d yspnea on e xe rtio n .C on tra st-e nh an ce d ch es t C T sc an (m ed ias tina l w in do w s ettin g) re vea ls s ha rp lym arg ina ted a n te rio r m ed ias tina l m ass w ith fa t, flu id , a nd so ft- tiss ue a tte nu a tion .N ote fa t-f lu id leve l w ith s oft-t iss ue n od ule flo ating a t in te rfa ce . A ls o n ote th in pe -r ip he ra l s of t- tis su e s ep ta ( a r r ow) a nd th in tu mo r c ap su le .

F ig . 4 .-4 -ye ar -o ld g ir l w ith ch es t pa in , fa tig ue , a nd in te rm it te nt f ev er . C o nt ra st -e n-hanced ch es t C T scan (m ed ia s tina l w ind ow se tting ) revea ls la rge le ft-s ide d a n te rio rm ed ia st ina l m ass tha t co nta in s so ft-tis su e a nd flu id a t ten ua tion . N ote so ft-tissu e n od-u le s in d epe nden t a sp ec t o f cy s t. A ls o n o te m a ss e ffec t, le ft low e r lobe co lla pse(ar row) , an d largele ft p leu ra l e ffu s io n . (R ep rin ted w ith pe rm iss ion from [81 )

F ig . 5 -38 -ye a r-o ld w om an w ho had che s t d iscom fo rt. C on tras t-e n hanced che s tC T s can (m ed ias tina l w in do w s ettin g) sh ow s la rg e m ed ias tina l m ass occ up yingm u lti pl e c om p ar tm e nt s w it h e nh an cin g s of t- tis su e s ep ta , t hi n p er ip he ra l s of t- tis su ec ap su le , a nd n od ula r s of t- ti ss ue c om p on en ts (ar rows) . N ote flo cc ule nt a nd p un c-t a te c a l ci fi c a ti o n s .

M ed ia s tin a l M a tu re T era tom a

A JR :16 9, O ctob er 1 99 7 98 7

F i g .6 - 5 9- y e ar - o ld w o m an w i t h p l eu r i ti ch e s t p a i n an d d y s pn e a o n e x e rt i o n. o n -trast-enhancedchestC T scan (m ed ia s t ina l w indow se ttin g ) re vea ls an te r io r m ed i-a stin al m as s o f s oft-t is su e a nd fa t a tte nu atio n. N ote th in s oft-t is su e s ep ta in centralfatty com ponen t o f tum or an d th ick no du la r s o ft t issu e (n (in m ed ia l aspe ct o f c ap -su le . A ls o no te sm all rightpleural e f fus ion .

(F igs . 2 and 3). A par t ia l o r com plete tis su ep lan e w as presen t be tw een the m ass and ad ja -cen t m ed iastina l structu res in 1 3 tum ors(2 0% ). A lobu la ted con to ur w as seen in 34masses ( 5 2% ) and a sm oo th b order w as seenin 25 m asses (38% ). Fo rty -six tum o rs (7 0% )w ere u n ilate ra l and 2 0 tum o rs (3 0% ) crossedth e m id line . Tw o m asses (3% ) w ere cen teredin th e m id line . M ulticom partm en tal ex ten sionw as o bserved in n in e lesions (14% ). A ltho ughno d isc repancy w as fou nd be tw een the af-

fec ted m ed ias tin al com partm en t on chestrad iog raphs com pared w ith CT stud ies , b ila t-e ra lity and m ulticom partm en ta l ex tens ionw ere m o re clea rly de linea ted on C T stud ies.

T he m ost freq uen t CT m anifesta tio n of m e-d iastina l m atu re te ra tom a w as tha t o f a he te ro -geneou s m ass con tain ing sof t- tis sue , flu id , fa tand calc ium attenu ation (F ig . 2 ). T h is com b i-na tion of a ttenu ation s w as p resen t in 26m asses (3 9% ). H ow ever, o the r com bina tio nsof CT attenua tions w ere a lso observed : so f t

tissue , flu id , an d fa t (F ig . 3 ) and sof t tissuean d flu id (F ig . 4) w ere th e nex t m ost frequen tcom bin atio ns , id en t ifie d in 16 m asse s ( 2 4%)and 10 m asses ( 15%) , respec tiv e ly . L ess fre -qu en tly observed w ere com bina tions o f so f ttissue , flu id , and ca lc ium seen in s ix tum ors(9% ) (F ig . 5) ; so ft tis su e and fa t in fiv e tu -m ors (8% ) (F ig . 6 ); an d soft tissue , fa t, an dca lc ium seen in th ree tum ors ( 5%) .

So ft-tissu e atte nua tio n w as se en in all tu -m ors bu t w a s the dom inan t com ponent (oc-

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M oelle r e t a l.

98 8 A JR :1 69 , O ctob er 1 99 7

cupy ing > 50% o f th e to ta l vo lum e o f theles ion) in o n ly tw o tum ors (3% ). In 65m ass es (9 8% ), so ft-tis sue e lem en ts ma rn -fested as curv ilinear tis su e lo cated in the pe-riphery o f the les ion correspon d ing to thetum or capsu le . T he periph eral so ft tis sue w aspredom inan tly th in (

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A JR :1 69 , O ctob er 1 997 98 9

as R ok itan sk i nod u les in pa tho lo g ic desc rip -tio ns of ov ar ian m atu re te ra tom as , h ave no tbeen frequen tly observed in prev io us desc rip -tio ns o f m ed ias tina l te ra tom as. T he se ries o fF r iedm an e t a l. in c lu ded on ly one pos te rio rm ed ias tin a l te ra tom a. T eratom as th roug hou tth e bo dy cou ld d isp lay d iffe ren t g ro ss fea tu resan d rad io log ic charac te ris tic s . T hu s, descr ip -tion s of im ag ing fea tu res b ased o n a stud y ofte ra tom as aris ing in m ultip le ana tom ic lo ca-tion s m ay no t be va lid . In our se ries, d ep en den tso ft-tissue nodu les w ere seen in on ly 13masses (20% ). S uzuk i e t a l. [2 1 ] desc ribed sixan te rio r m ed iastina l te ra tom as , th ree of w hichmanifes ted as th ick -w alled cysts . H ow ever,ou r se ries show ed tha t the m ajo rity o f les ions(88% ) had th in w alls.

M atu re te ra tom as in our se ries ty p icallyman ifes ted a s un ila tera l, sha rp ly m a rg inated ,lobu la ted , he te rogeneo us, an te rio r m ed ias tina lm asses. CT revea led flu id -con ta in in g (cys tic)a reas in 88% of cases, co rre la tin g w ith th eh igh frequ en cy of th is find ing (97% ) in th egross spec im ens . F ifty -s ix les io ns (85% ) in -c luded m ultilo cu la r cys tic a reas separa ted byth in -tissue sep ta . CT frequen tly revea led fa t(76% ) and ca lc ium ( 5 3%) w ith in the lesion s.O ur find ings con trad ic t a rep ort [21 ] tha tsta tes th at fa t is in fre quen tly seen in m aturete ra tom as, as it w as presen t in m ore than th reefou rths o f tum ors . In add ition , CT revea ledfa t-flu id leve ls in sev en m asses (1 1% ), s ix o fw h ich w ere no t de tec ted rad io graph ica lly .T h is h igh ly spec ific fin d ing resu lts w henlip id -rich flu id p roduced by ec toderm al tis -su es sep arates from serou s flu id sec re ted byendod erm al e lem en ts an d floa ts over the resto f the liq u id in th e cys t [22].

C om b in ations of m ultip le -tissue elem en tsw ith in a cys tic m ed ias tin a l m ass sugges t thed iagnos is o f m atu re te ra tom a. A lthou gh Su-zuk i e t a l. [21 ] rep orted on ly one tum or (17% )w ith so ft-tissue , f lu id , fa t, and ca lc ium atten u-a tion , th is com bina tio n of CT atten ua tion sw as the m ost f requen tly en co un te red in ourse ries, seen in 26 m asses (39% ). In te resting ly ,15 % o f les ions m an ifes ted as cys tic m assesw ithou t fa t o r ca lc ium attenu ation . N in e ofthese lesions w ere m u ltilocu la r and one w asu n ilo cu lar . T h erefo re , the d iagnos is o f m atu rete ra tom a sh ou ld a lso be cons idered in cys tican te rio r m ed ias tina l m asses th at lack fa t o rca lc ium atten ua tio n on CT scans.

A partial o r com ple te tis sue p lane b e tw eenthe lesion and ad jacen t m ed iastina l struc tu resw as n o ted in on ly on e fifth o f tum ors, pe rhapsb ecause te ra tom as comm on ly ad here to ad ja -cen t m ed iastina l s truc tu res [1 0 , 2 3]. CT scans

prov ide in fo rm ation concern ing assoc iatedparen ch ym al, p leu ra l, o r perica rd ia l d iseaseseen in 35% , 23% , and 11% of cases in ourse ries , respec tive ly [20 , 2 4]. It is d ifficu lt toaccoun t fo r the h ig h frequency (27% ) of p leu -ra l e ffus io n , pe rica rd ia l e ffusion , o r bo th inou r se ries because flu id ana lys is w as no t per-fo rm ed for an y pa tien t. T um o r rup tu re in to thead jacen t p leu ra l o r pericard ial cav itie s w as n o tdesc ribed in e ithe r the su rgery or g ross p atho l-og y repo rt o f any lesion in the se ries. E ffu -sion s assoc ia ted w ith th orac ic neop lasm s ,inc lud ing te ra tom a, m ig h t resu lt from in -c reased cap illa ry perm eab ility , lym pha tic ob-struction, or bo th [25-27].

CT is th e im ag ing techn ique o f cho ice inthe eva lua tion o f the abn orm al m ed ias tin um .It exqu is ite ly show s th e loca tio n and ex ten to f d isease as w ell as in tr in sic elem en ts o f thelesion , inc lud in g soft tissue , fa t, flu id , andca lc ifica tio n [8 , 14 , 17 , 28]. M R im aging re -vea led m asses o f he te rogeneo us sign al in ten -sity con sis ten t w ith flu id in 88% of tum orsand w ith fat in 63% of tum ors . T era tom as inour se ries m an ifested son ograph ica lly ascom plex m asses w ith cy stic a reas in a ll s ixles ions (100% ). H ow ever, M R im aging andson ograph y d id no t con tribu te ad d ition a l in -fo rm ation in any case .

T he d iffe ren tia l d iagnos is o f fa t-con ta in in gm edias tina l m asses inc ludes m ed ias tin al fa tpad , m ed ias tina l lip om ato sis , lipom a, om enta lhe rn ia tio n , thym olipom a, and liposa rcom a[2 9]. H ow ever, m atu re teratom as are eas ilyd istingu ished from these lesions by the ir cys-tic appearance w ith predom in an ce of flu id e l-em en ts and h igh frequ ency of ca lc ifica tion ,find ings read ily seen o n C T scans .

In con clus ion , m ed ias tina l m atu re te ra to -m as typ ica lly occu r in sym ptom atic pa tien ts .O n CT , these tum o rs a re h ete ro geneous ,sharp ly m arg ina ted , sp herica l o r lo bu la tedan te rio r m ed ias tina l m asses w ith cystic com -ponen ts. T he cys tic a reas a re frequ en tlycom partm en ta lized b y th in -tis su e sep ta(8 5% ), bu t nod u la r so ft-tis su e e lem en ts(6 7% ) are a lso seen . S oft tissue is a lw ays v i-sua lized and is ra re ly the dom inan t com po -n en t o f the tum or ; flu id is comm on (89% )and th e d om inan t com pon en t in 8 0% ofm asses . Fa t, ca lc ifica tio n , o r b o th are p resen tin 85% of tum ors. C y stic les ions w ithou t fa to r ca lcifica tio n accou n t fo r 15% of les io ns.T h e m ost f requen t com b in ation o f CT alien -u ations is so ft tissue , flu id , fa t, and ca lcium ,seen in 39% of m asses . F a t-flu id leve ls a rev isua lized in 11 % o f m asses . CT is use fu l fo rsugges ting the correc t d iag nos is in m os t pa-

tien ts, based on the h igh freq uency o f cy stica reas and fa t seen in m atu re te ra tom as, bu tM R im aging an d sonograp hy , w h en per-fo rm ed as anc illa ry stud ies , p rov ide no add i-tiona l use fu l in fo rm atio n.

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Notice to A u tho rsA uthors o f accep ted m anuscrip ts can now rece ive g alley proofs v ia em ail. Th e au thors sys tem m u st be ab le to read B in-H ex file s and have vers ion 3 .0 of A dobe A cro ba t R ead er. Th e A RRS W eb site (h ttp ://www .arrs .o rg ) has a link to theA dob e W eb site , w here au th ors can down lo ad free cop ies o f th e m os t recen t vers ion of the reader.

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