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1
Department of Radiology, St. Bartholomews Hospital, West Smithfield, London,
EC1A 7BE, England.
2
Department of Radiology, Royal Marsden Hospital, Downs Rd., Sutton, Surrey,
SM2 5PT, England.
3
Department of Oncological Gynaecology, St. Bartholomews Hospital, West
Smithfield, London, EC1A 7BE, England.
4
Department of Academic Radiology, St. Bartholomews Hospital, West Smithfield,
London, EC1A 7BE, England.
Received April 30, 2001;
accepted after revision June 22, 2001.
Address correspondence to A. Sahdev.
Abstract
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MATERIALS AND METHODS. MR images from all patients with histologically proven uterine sarcomas scanned between 1993 and 2000 were reviewed. Tumor size, its relationship to the uterus, signal characteristics, and enhancement pattern after IV injection of gadolinium were noted.
RESULTS. Twenty-five scans from 22 patients were reviewed. Findings from the scans included 11 leiomyosarcomas, five mixed müllerian tumors, two rhabdosarcomas, and four endometrial stromal sarcomas. Two patterns of disease were observed, including a characteristic large heterogenous pelvic mass (n = 17) and an endometrial mass indistinguishable from endometrial carcinoma (n = 8). On T2-weighted images, the large masses were characteristically of low or intermediate background signal intensity with pockets of very high T2 signal. The areas of high T2 signal corresponded to cystic necrosis in the tumor. Pockets of high T1-weighted signal corresponded to hemorrhage. Gadolinium enhancement was present in the solid components of all tumors. This pattern was observed in all recurrent sarcomas. Some correlation was shown between the histologic subtypes and the MR imaging appearances.
CONCLUSION. Uterine sarcomas show two patterns on MR imaging. The most common presentation is a large heterogenous mass. However, sarcomas can mimic endometrial carcinoma.
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Thirteen patients underwent MR imaging at presentation only; four were diagnosed with leiomyosarcomas, two with rhabdosarcomas, four with mixed müllerian tumors, and three with endometrial stromal sarcomas. Three patients underwent MR imaging at the original presentation and again for recurrent disease; two of these patients had leiomyosarcomas and one had a mixed müllerian tumor. Six patients underwent MR imaging for recurrent disease only; five of these patients had leiomyosarcomas and one had endometrial stromal sarcoma.
MR Imaging Technique
The MR imaging studies were performed using a Signa Horizon 1.5-T unit
(General Electric Medical Systems, Milwaukee, WI). All studies were acquired
using a pelvic phased array coil. All patients underwent axial T1-weighted
spin-echo (TR range/TE, 400-500/9) and axial and sagittal fast spin-echo
T2-weighted imaging (4000/95-105; echo train, 8). In 11 patients, T1-weighted
fat-saturated spin-echo images (400-600/9-14), before and after an antecubital
IV bolus injection of 0.1 mmol/kg of body weight of gadoteric acid (Dotarem;
Guerbet, Buckinghamshire, United Kingdom) enhancement, were also obtained. A
single-phase scan was acquired after injection of IV gadolinium. The imaging
matrix for the axial and sagittal T2-weighted images and the T1-weighted
fat-saturated images was 512 x 256. For the axial T1-weighted images,
the matrix was 256 x 256. The section thickness for all images was 5-7
mm with an intersection gap of 1-2 mm.
Imaging Interpretation
Scans were reviewed by three radiologists who reached a consensus on site,
size, T1-weighted and T2-weighted signal intensity, internal architecture, and
enhancement characteristics of the tumor. The T1-weighted and T2-weighted
signal intensity and enhancement characteristics of the tumor were compared
with normal myometrium and endometrium. Myometrial and parametrial invasion
was noted. Myometrial invasion was diagnosed where the loss of the junctional
zone or the tumor was seen extending into the myometrium. Definite parametrial
extension was documented when tumor strands were observed extending into the
parametrial fat. Parametrial invasion was suspected if no normal
circumferential myometrial tissue was seen containing the tumor in the uterus.
Pelvic nodes, pelvic metastasis, and ascites were documented.
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Seventeen (68%) of the 25 scans (eight at original presentation and nine with recurrent pelvic sarcoma) showed large pelvic masses (Figs. 1,2,3,4,5,6A,6B). These masses all showed a characteristic appearance of background intermediate or low T1 signal intensity with small areas of high T1 signal intensity. On T2-weighted images, the masses were heterogenous and contained background whorls of intermediate or low signal intensity and pockets of high signal intensity. The high T2 signal intensity pockets were of variable sizes and coalesced into larger pools in three patients (Figs. 1,2,3,4,5). Of the eight patients with large masses scanned only at presentation, five had leiomyosarcomas, two had rhabdosarcomas, and one had mixed müllerian tumors.
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All patients with recurrent disease had large heterogenous pelvic masses, irrespective of the histology. Among these nine patients, seven had recurrent leiomyosarcomas, one had mixed müllerian tumors, and one had endometrial stromal sarcoma.
The second pattern seen on MR imaging was an endometrial mass indistinguishable from an endometrial carcinoma. This pattern was seen in eight (32%) of the 25 scans (Fig. 7). Six patients presented with a large mass (>2 cm) (one with leiomyosarcoma, two with endometrial stromal sarcomas, and three with mixed müllerian tumors) and two with a small endometrial mass (one with endometrial stromal sarcoma and one with mixed müllerian tumor). The endometrial masses had intermediate T1 and T2 signal intensity. Myometrial involvement was seen in seven of the endometrial masses, of which four were mixed müllerian tumors, one was a leiomyosarcoma, and two were endometrial stromal sarcomas.
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Thirteen enhanced scans after IV gadolinium injection were available for review. Seven patients had large pelvic masses and six had endometrial masses. Avid tumor enhancement was present in six of the seven large pelvic masses (five leiomyosarcomas, one mixed müllerian tumor) and in five of the six endometrial masses (one leiomyosarcoma, three mixed müllerian tumors, one endometrial stromal sarcoma). One of the seven large masses showed only moderate enhancement (leiomyosarcoma) and one of the six endometrial masses showed late tumor enhancement (endometrial stromal sarcoma).
Five of the 22 patients had ascites, four at the time of original presentation (two leiomyosarcomas, one mixed müllerian tumor, and one rhabdosarcoma) and one with recurrent disease (mixed müllerian tumor) associated with widespread pelvic and peritoneal metastases. At presentation, no patient had pelvic lymph node enlargement exceeding 8 mm. Five patients had metastases to the ovaries and the peritoneum (three leiomyosarcomas, three mixed müllerian tumors). One patient (with an endometrial stromal sarcoma) had tumor encroachment of the sacral neural foraminae, a large sacral canal mass, and invasion of the erector spinii muscles.
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Our study has shown that on MR imaging two clear patterns of presentation emerge that have some correlation to the histologic subtype. In our study, large heterogenous pelvic masses had the most frequent appearance on MR imaging (n = 17). These appearances included all except one of the leiomyosarcomas, both rhabdosarcomas, and all recurrent sarcomas (including one mixed müllerian tumor and one endometrial stromal sarcoma). The remaining eight studies all showed endometrial masses. Four of the masses were mixed müllerian tumors, three endometrial stromal sarcomas, and one leiomyosarcoma.
In our series, leiomyosarcomas presented as large masses. Six leiomyosarcomas were found at original presentation, replacing the normal architecture of the uterus with the resultant mass and showing a background of low or intermediate T1 signal intensity with scattered pockets of high signal intensity. On T2-weighted images, a background of intermediate signal intensity with pockets of high signal intensity was found. Four leiomyosarcomas were large recurrent pelvic masses, with appearances similar to the primary uterine leiomyosarcomas just described. One leiomyosarcoma appeared as a large endometrial mass. On histology of the hysterectomy specimen, this tumor was a polypoid mass arising from the posterior myometrium of the uterine fundus, invading the endometrium and deep myometrium. Away from the tumor, the endometrium in this patient was normal.
In our study and in a previous histologic description [1], the areas of high T1 and T2 signal intensity corresponded to hemorrhage, whereas regions of low T1 and high T2 signal intensity corresponded to areas of cystic necrosis in the tumor.
Shapeero and Hricak [3] previously described the MR imaging features of seven mixed müllerian tumors as broad-based endometrial masses with myometrial invasion. In a further study, DeSaia and Pecorelli [5] showed that 50% of mixed müllerian tumors had deep myometrial invasions and 33% had lymph node and metastatic disease at surgery. This finding contrasted with that of Worthington et al. [6], who identified on MR imaging that three of four mixed müllerian tumors were large masses, replacing the normal uterine architecture, and the remaining one was an endometrial mass. Four of the five mixed müllerian tumors in our series were endometrial masses and the fifth was a large uterine mass obliterating the normal uterine architecture. All four endometrial masses were indistinguishable on MR imaging from endometrial carcinoma at the time of presentation. Three of the four large endometrial mixed müllerian tumors showed myometrial invasion, and the small endometrial mass did not. The former three large endometrial masses presented with postmenopausal vaginal bleeding, and the smaller mixed müllerian tumor presented as part of a palpable pelvic mass associated with the large benign leiomyomas, with the small early sarcoma as an incidental postoperative histologic finding. Our findings reflect features from all three studies, with the majority of our primary mixed müllerian tumors (4/5) presenting as endometrial masses. In our series, five (20%) of the 25 sarcomas were mixed müllerian tumors. This probably reflects a local MR imaging referral pattern for endometrial masses, rather than the true disease prevalence.
One patient with a large endometrial mass re-presented with recurrent disease 1 year after a hysterectomy for the original mixed müllerian tumor. Her disease recurrence consisted of a large pelvic mass, resembling the leiomyosarcomas. Because large sarcomatous lesions and all the recurrent masses resemble leiomyosarcomas, it is likely that the features of hemorrhage and cystic necrosis that confer these lesions their characteristic appearance develop as the tumor mass increases in size. The smaller lesions, therefore, mimic endometrial carcinomas, whereas the larger tumors are characteristic pelvic masses resembling leiomyosarcomas.
Endometrial stromal sarcoma is composed almost exclusively of neoplastic stromal cells. The high-grade tumors are aggressive and rapidly metastasizing, whereas the low-grade tumors are indolent, with distant metastasis being rare. The two types of tumors are distinctly different and not part of a disease spectrum [7]. Our four patients had high-grade endometrial stromal sarcomas. The largest endometrial stromal sarcoma presented with a large recurrent pelvic mass similar to the leiomyosarcomas. The smaller tumors mimicked endometrial carcinoma. This appearance was also described by Koyoma et al. [4] who showed low-grade endometrial stromal sarcomas mimicking benign leiomyomas on imaging, and high-grade endometrial stromal sarcomas presented as invasive endometrial masses indistinguishable from endometrial carcinoma.
Little has appeared in the literature regarding the imaging features of adult uterine rhabdosarcomas. In our study, both tumors presented as large uterine masses with a characteristic appearance. Both tumors had an intermediate marbled background T2 signal intensity with pockets of high T2 signal intensity. T1-weighted images revealed a homogenous low-signal-intensity mass.
In summary, uterine sarcomas reviewed in our series followed two patterns of presentation. The dominant pattern is a large heterogenous mass. At original presentation, the mass is most likely to be a leiomyosarcoma or a rhabdosarcoma. All recurrent diseases manifest with a large heterogenous mass irrespective of the original mode of presentation. Invasive endometrial masses were the second observed pattern. These were mainly mixed müllerian tumors or endometrial stromal sarcomas. Although diverse, these MR imaging features should alert the radiologist to the diagnosis of a uterine sarcoma.
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