CT Appearance ofUterine l

Javier Casillas, MD

Ronald C. Joseph, MD

JorgeJ. Guerra, Jr. MD

Uterine leiomyomas, commonly known as fibroids, are one of the

most common pelvic tumors found in women. Ultrasonography is the

primary modality for evaluating leiomyomas. However, frequently

these tumors are not accompanied by symptoms, and they are found

incidentally during computed tomographic (CT) examinations per-

formed for other indications. Because leiomyomas may first be noted

on CT scans, radiologists should become familiar with their character-

istic appearance. The authors describe the CT findings of uterine leio-

myomas and their secondary changes, including cystic degeneration,

calcification, infection, necrosis, fatty degeneration, and sarcomatous

degeneration.

U INTRODUCTIONUterine leiomyoma, one of the most common pelvic tumors in women, is often en-

countered as an incidental finding on computed tomographic (CT) scans obtainedfor other indications or in the workup of patients with a pelvic mass. It is there-

fore important for radiologists to become familiar with the spectrum of their ap-pearance.

In our 6-year experience, which encompasses over 6,000 CT scans of the abdo-men and pelvis, we have encountered 97 cases of histologically proved uterineleiomyomas. The purpose of this article is to review the CT findings of these tu-mors, with emphasis on the significance of different degrees of attenuation detect-

ed within them.

U GENERAL CHARACTERISTICSUterine leiomyomas are commonly called fibroids, although they derive not from

fibrous tissue but from smooth muscle cells of the uterus ( 1 ) . They occur morefrequently among black and other dark-skinned populations (2).

Clinically, uterine leiomyomas are commonly symptomless, but they may occuras a palpable mass, accompanied by bleeding or pain, or with symptoms secondary

to compression of the mass on the bladder, uterus, or rectum. Patients with leio-myomas may present with hypermenorrhea, although the exact mechanism by

which these tumors produce abnormal bleeding is still unknown. Hypermenor-rhea is a common indication for surgery; other indications include rapid tumor

Index terms: Myoma. 854 .3 1 5 #{149}Uterine neoplasms. 854 .3 1 5 #{149}Uterine neoplasms, CT, 854 . 1 2 1 1 #{149}Uterus, CT,

854.1211

RadloGraphics 1990; 10:999-1007

I From the Department ofRadiology. University ofMiami School ofMedicine, 161 1 NW 12th Ave. Miami, FL 33136

and the Department of Radiology, Jackson Memorial Medical Center, Miami. From the 1989 RSNA scientific assembly.

Received May 7, 1990; revision requestedjune 6 and receivedjuly 20; acceptedJul� 23. Address reprint requests

toJ.C.

casNA, 1990

999

Figures 1-3. (1) Diagram illustrates the variouspossible locations of leiomyomas in the uterus.(2) Pathologic specimen of an intramural leio-myoma (arrow) . UC = uterine cavity. (3) Patho-

logic specimen of multiple subserosal leiomyo-

mas (55 ) . Arrow indicates uterine cavity.

2. 3.

1000 U RadioGrapbics U Casillas et al Volume 10 Number 6

growth, pelvic pain, pressure, and impairedfertility (1 ,2) . The presence of multiple leio-myomas during pregnancy increases the fre-

quency of malpresentation, retained placen-ta, and premature uterine contractions (3).Leiomyomas can markedly enlarge, a charac-

teristic that makes differentiation of these tu-mors from other pelvic or abdominal masses

sometimes difficult. Almost any intrapelvicabnormality needs to be differentiated from

this condition.

Leiomyomas are usually sharply circum-

scribed, unencapsulated but discrete, round,firm, gray-white masses; cut specimens havea characteristic whorled surface. These tu-

mors are commonly multiple and of varioussizes. A solitary leiomyoma is found in only

2% of patients, and the number of these tu-mors may reach the hundreds. They rarelydevelop after menopause.

The location of leiomyomas in the uterusis variable (Fig 1) . Those embedded within

the myometrium are referred to as intramural(Fig 2) . When they occur beneath the cover-ing peritoneum of the uterine corpus, they

are called subserosal (Fig 3) . Some leiomyo-mas occur in immediate proximity to the en-dometrium and are designated as submuco-sal. Frequently, the subserosal and submuco-

sal masses protrude from the outer contour

of the uterus and into the endometrial cavity,

respectively. Such leiomyomas may become

4b. 4c.

Figures 4, 5. (4) CT scans of the normal uterus (U). B = bladder. (a) Unenhanced CT scan demonstrates

the uterus. (b) In a CT scan of the pelvis obtained before intravenous administration of contrast material,the attentuation of the uterus (cursor 1 ) is 77.7 HU. (c) On the contrast-enhanced scan, the attenuation of

the uterus has increased to 1 26.5 HU. Attenuation of the soft tissues (cursor 2 ) has not significantlychanged (55.3 HU in b vs 5 1 .9 HU in c). (5) CT scan of postpartum uterus (U) reveals fluid in endometri-

a! cavity (F and arrow).

November 1990 Casillas et al U Ra4ioGrapbics U 1001

pedunculated. The subserosal type may pro-trude into the broad ligament to create an in-traligamentous leiomyoma (1).

Hyaline degeneration is seen in almost alluterine leiomyomas. Other secondary

changes include cystic degeneration, calcifi-

cation, infection, necrosis, fatty degenera-tion, or sarcomatous transformation (1,2).

U NORMAL ANATOMY OF THEUTERUSThe uterus is a pear-shaped organ, usuallyidentified on CT scans in the midline be-tween the bladder and the rectum, depend-ing on the degree of bladder and rectal dis-

tention and on normal anatomic variations(Fig 4) (4) . On CT scans obtained after intra-venous administration of contrast material,normal myometrium enhances more than

other pelvic tissues (Fig 4b, 4c) (5) . At soft-tissue window settings, the normal uterus ap-

pears smooth in contour and uniform in at-

tenuation, although central uterine fluid may

be seen in the absence of disease or in thepostpartum uterus (Fig 5).

5. y.

1002 U RadioGrapbks U Casillas et al Volume 10 Number 6

Figures 6-9. (6) CT scan shows enlarged uterus (U), with a lobulated contour, secondary to a leio-

myoma (arrow) . (7) CT scan of another patient demonstrates a submucosal leiomyoma (arrow) producingdeformity of the endometrial cavity. (8) CT scan obtained due to hydrocolpos secondary to cervical steno-sis incidentally reveals a small calcified uterine leiomyoma (arrow) . (9) CT scan obtained through themidabdomen in a patient with increasing abdominal girth demonstrates a giant abdominopelvic soft-tissuemass (M ) and associated bilateral hydronephrosis (H).

Figures 10, 11. (10) CT scan demonstrates hyalmne degeneration of uterine leiomyomas. Arrow indicatescystic areas. (11) CT scan shows a leiomyoma with atypically high attenuation. No malignant cells werefound in pathologic specimen.

November 1990 Casillas et al U RadioGrapbics U 1003

U CT CHARACTERISTICS OF UTERINELEIOMYOMAS

. Uterine Enlargement with ContourDeformityAn enlarged uterus and a deformed uterine

contour are the most common CT findings ofleiomyomas (Fig 6) . Leiomyomas usually

have a uniformly solid consistency, with at-tenuation values similar to those of unin-volved uterus (6) . Although uterine enlarge-ment may be a prominent feature, minimaluterine enlargement is difficult to diagnose

with CT; therefore, uterine size alone is not auseful criterion for the differential diagnosis

of leiomyoma (4) . Alterations in contour orlobulations are identified more often in the

uterine fundus; however, such changes maybe seen in the body or in the lower segmentof the uterus. Leiomyomas can also occur asan intracavitary mass obliterating the uterinecavity (Fig 7).

Leiomyomas can be small (Fig 8) or giant

(Fig 9) , homogeneous or inhomogeneous,pelvic or abdominopelvic masses. Thegrowth of uterine leiomyomas is estrogen de-pendent. They do not appear until after men-

arche and usually diminish in size aftermenopause. They can increase suddenly in

size during pregnancy or if the patients are

taking birth control pills (1 , 3 , 5) . Calcifica-

tion or cystic changes may be noted within

large masses.

. Hyaline and Cystic DegenerationHyaline degeneration is the most common of

all secondary changes seen in cases of leio-

myomas ( 1 , 2 ,4) . It may involve broad areas

of the tumor. The tendency of hyaline degen-

eration is toward liquefication, and in ex-

treme cases practically all of the original tu-mor is thus involved and converted into a

large cystic cavity, a state that clinically sim-

ulates pregnancy or an ovarian cyst. A leio-

myoma with necrosis or degeneration may be

seen on CT scans as a low-attenuation mass in

the uterus (Fig 1 0) . Occasionally, areas of

high attenuation may be seen in atypical

leiomyomas of the uterus (Fig 1 1).

-�1

E�.,i �

Figures 12-14. (12) CT scan demonstrates en-larged uterus (U) and popcorn calcifications in aleiomyoma (arrow) . Note bilateral ovariancysts (C) . (13) CT scan of a 4 1 -year-old patientshows multiple subserosal and intramural uterineleiomyomas; most of them are calcified (arrows).(14) CT scan reveals uterine leiomyoma with cal-cification of solid mass type (arrow) . Contour de-formity of the uterus caused by other smaller leio-myomas (arrowheads) is also evident.

14.

1004 U Ra4ioGrapbics U Casillas et al Volume 10 Number 6

. CalcificationCalcification is likely to occur in leiomyo-mas in the presence of circulatory distur-

bances, such as those commonly found in

older women (2) . This dystrophic calcifica-

lion of solid mass type usually has a mottledappearance with no well-defined curvilinear

rim (Fig 1 2) . There are, however, calcifica-lions in leiomyomas that have a well-defined,

thin, high-attenuation rim with relatively lit-

tie internal calcification, and they can bemottled, whorled, or streaked (Fig 13).

Although uterine leiomyomas are apt to be

multiple in a given patient, calcification may

be present in only one of the tumors (Fig1 4) . The soft-tissue mass of an individualleiomyoma is frequently larger than the vol-

ume of the calcification, merely reflecting

the fact that calcification may be limited toonly a part of the tumor (7).

The presence of calcification in a uterinemass is the most specific sign of a leiomyoma(6); however, this finding is reportedly un-

common (7) . In one series, calcifications

were found in only 3%-5% of leiomyomas

(8). In our experience, 10% ofuterine leio-myomas contained calcifications.

16a. 16b.Figures 15, 16. (15a) CT scan of an infected and partially necrosed leiomyoma shows pocket of gaswithin the mass (arrow) and peripheral rim of calcification. (15b) Pathologic specimen shows a large ne-

crotic area (arrow). (16) CT scans of a 42-year-old patient with a 1 -month history of heavy vaginal bleed-ing and lower abdominal pain. (a) Section through fundus of the uterus (U) shows fluid in endometrial

cavity (arrow) . (b) Section through lower pelvis shows the leiomyoma (arrow) protruding through thecervix. At surgery an ulcerated, submucosal pedunculated uterine leiomyoma protruding through the cer-vix was found.

November 1990 Caslllas et al U RadioGraphics U 1005

. Infection and NecrosisInfection is more common in submucosal

leiomyomas because their blood supply isfrequently insufficient to support the tumormass (2) . Their exposed position adjacent tothe uterine lumen predisposes them to as-

cending infection. Occasionally, when theleiomyoma is infected, the central core maybe filled with purulent material or gas

(Fig 15) (8).Subserosal and submucosal leiomyomas

may become pedunculated and may undergo

torsion of the pedicle, with subsequent in-

farction, degeneration, necrosis, and poten-

tial infection (Fig 1 6) . Occasionally, such bi-

zarre tumors adhere to surrounding struc-tures or omentum, develop an auxiliary

blood supply, and lose their original attach-

ment to the uterus. They are sometimes

called ‘ ‘parasitic” lelomyomas (1).

C.

1006 U RadioGrapbks U Casillas et al Volume 10 Number 6

Figure 17. CT scans of a leiomyosarcoma.(a) Section through the upper pelvis showsthe mass (M ) to the right of the rectosig-moid (R ) . (b) Sections through the lowerpelvis show the mass (M ) extending intothe ischiorectal fossa and displacing the rec-tum to the left. B bladder. (c) Pathologicspecimen. At surgery, a large mass arisingfrom the lower segment of the uterus andextending into the ischiorectal fossa wasfound. Leiomyosarcoma was diagnosed fromhistologic results. There is no reliable way

to differentiate a leiomyoma from a leio-myosarcoma on CT scans.

. Sarcomatous DegenerationLeiomyosarcoma is an infrequent complica-tion of leiomyoma, occurring in less that 1%of cases. Malignancy in a leiomyoma is sel-dom diagnosed preoperatively because there

are no characteristic symptoms. On CT scans,it is impossible to distinguish this entity

from a preexisting leiomyoma. Suddenaccelerated growth of a previously static tu-mor or postmenopausal enlargement of auterine mass should suggest this possibility

(Fig 17) (8).

U CONCLUSIONThis report illustrates the various CT appear-

ances of uterine leiomyomas, with emphasison the significance of various degrees of at-tenuation that may be seen within them. Al-though uterine enlargement and contour de-formity are the most common CT findings ofthese masses, calcification is the most specif-

ic CT sign of a leiomyoma.Noncalcified leiomyomas may be confused

with other pelvic masses on CT scans. Distin-

guishing between such leiomyomas and amalignant uterine neoplasm is difficult. Dif-

ferentiation of interstitial leiomyoma from

M

U‘A�:

November 1990 Casillas et al U RadioGrapbks U 1007

Figure 18. CT scan shows a large ovarian mass(M ) with cystic component inseparable from theuterus (U) . This mass has a CT appearance similar

to that of a leiomyoma.

uterine adenomyosis is also difficult, espe-

cially since these two lesions are frequently

associated (9), and is probably beyond the

current resolution of CT. Other pathologic

conditions involving the uterus, such as en-dometrial or cervical carcinoma, may also

coexist with uterine leiomyomas. In addi-

lion, extrauterine masses, in particular, a va-riety of solid or cystic ovarian tumors, maybe misdiagnosed as subserosal or peduncu-lated uterine leiomyomas (Fig 18).

Although it is useful to be familiar with

the different appearance of uterine leiomyo-mas on CT scans, it is important to remember

that CT is not the primary modality for evalu-

ating or diagnosing leiomyomas. Ultrasonog-

raphy (US) is the first-line imaging study.When findings from US are indeterminate,magnetic resonance imaging is the nextchoice, because it offers greater sensitivity

(1 0) and specificity than CT.

riowledgments: We thank Bill Burke, radi-Vdepartment photographer, and Hilda Cebal-

! secretary, for their assistance in the prepara-

� of this manuscript.

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