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Case Report |
1 Department of Diagnostic Imaging, Rabin Medical Center, Beilinson Campus,
Sackler School of Medicine, University of Tel Aviv, Kaplan St., Petach-Tikva
49100, Israel.
2 Department of Surgery, Rabin Medical Center, Sackler School of Medicine,
University of Tel Aviv, Tel Aviv, Israel.
3 Department of Gynecology-Oncology, Rabin Medical Center, Sackler School of
Medicine, University of Tel Aviv, Tel Aviv, Israel.
Received February 12, 2005;
accepted after revision June 16, 2005.
Address correspondence to O. Benjaminov.
Keywords: CT • MRI • myxoid liposarcoma • oncologic imaging • pelvic imaging • sonography
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Establishing the correct diagnosis in cases of myxoid liposarcoma using imaging may be difficult. On images obtained without the administration of contrast material, the tumor may mimic a fluid-filled cyst on both CT and MRI, and the tumor lacks the signal intensity of fat. Sonography may help in establishing the presence of solid components and in differentiating between a cyst and a solid tumor. The combination of different imaging techniques helps in defining the extent of the tumor for preoperative planning.
We present an unusual case of a giant myxoid retroperitoneal and pelvic liposarcoma that presented as a large buttock mass (Fig. 1A). The combined information gathered from MRI, CT, and sonography was crucial for defining the extent of the tumor and for preoperative planning.
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A sonogram of the buttock revealed a large hypoechoic avascular mass, but its exact margins could not be defined. Transvaginal sonography showed the complex cystic nature of the tumor; however, the genital organs could not be identified because of the large dimensions of the mass.
After sonography, CT of the chest, abdomen, and pelvis was performed. CT depicted a large well-defined cystic mass with thin septations in the anterior and lower abdominal cavity that was causing small loops of bowel to deviate posteriorly (Figs. 1B and 1C). The mass extended deep into the pelvis, compressing and deviating the sigmoid colon and rectum to the right. It further herniated the perineum and extended into the left ischiorectal fossa. The uterus was unremarkable. At that point, we assumed that this mass was an adnexal mass.
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MRI was then performed; it showed an extensive soft-tissue mass (Figs. 1D, 1E, 1F, 1G, 1H, 1I, 1J). The uterus and bladder were deviated anteriorly. The mass was shown to herniate through the perineum into the left ischiorectal fossa, and the pelvic diaphragm could easily be defined. The mass was composed of cystic and solid components. The right ovary was well defined; however, the left ovary could not be identified.
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At laparotomy, a giant retroperitoneal mass was identified (Fig. 1M): It extended from the left gutter (compartment I) and crossed the midline (compartment II) to the right side (compartment III), pushing the sigmoid and rectum toward the right gutter and right pelvic wall. The midline portion of the mass pushed the peritoneum between the bladder and the uterus up into the abdomen, lying over the stomach and intestines. The bladder and uterus were pushed toward the right pelvic wall. A fourth component (compartment IV) continuous to the same tumor mass extended down to the perineum, deviating the rectum laterally to the right, splitting and protruding through the levator muscle and into the left ischiorectal fossa, and prolapsing through the left gluteus.
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Surgery included laparotomy through a large median incision. The uterus, ovarian vessels, salpinges, ovaries, and bladder were dissected off the specimen. The serosa of the rectosigmoid area was removed with the tumor. Then, by a left pararectal approach, the lower-most protrusion of the tumor was released from the ischiorectal fat, levator muscle fibers, and pararectal tissue. At the end of this stage, the whole tumor mass was removed en bloc transabdominally without compromising the radial margins, excluding those of the pararectal area.
The patient's postoperative course, including 3 days in the ICU, was uneventful. Histology analysis showed that the mass consisted of a myxoid matrix as the predominant component with small amounts of mature fat, so the diagnosis of myxoid liposarcoma was confirmed.
To date, 32 months of follow-up has yielded no evidence of recurrence. The patient is completely continent, but her urinary flow rate is decreased.
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Relatively little information about soft-tissue sarcomas of the female pelvis, particularly myxoid liposarcomas, can be found in the literature [3]. Only a few reports about giant retroperitoneal and pelvic liposarcomas causing abdominal distention have been published in the literature [3-6]. Cases of liposarcomas involving the thigh and pelvis have been described [3]. The case we describe is a huge liposarcoma in a very young woman that involved the retroperitoneum and pelvis, herniating the pelvic floor to present as a large painless buttock mass. The full extent of the tumor was not visible until the findings from several imaging techniques were combined.
Curative resection remains the main treatment for primary and recurrent liposarcomas, and determining the anatomic location and extent of the masses is essential for surgical planning. This too was made possible only by the combination of information collected from sonography, transvaginal sonography, CT, and MRI. Therefore, imaging plays a key role in the preoperative assessment, and for huge tumors, a multi-imaging technique approach is often necessary. In our patient, the preoperative imaging evaluation played a major role in achieving an en bloc tumor mass resection and in completely preserving the pelvic organs.
Sonography is usually the first technique used. It is useful for characterizing the tissue nature of the mass and for differentiating solid from cystic masses. On sonography, a specific pattern of multiple, evenly distributed echogenic lines within the tumor that correspond to fatty components within the tumor may be observed [7]. Some myxoid liposarcomas may appear as complex cystic masses. Because of their size and extent, defining their exact borders and assessing involvement of adjacent organs may be difficult. The transvaginal sonography estimation may be difficult because of the large dimensions of the tumor and deviation of pelvic organs. Myxoid liposarcomas may be misdiagnosed as adnexal masses [6], as happened in our patient. Initially, we could not see the ovaries, and because of the rarity of soft-tissue sarcomas [3] involving the pelvis, we assumed the mass was an adnexal mass. On the other hand, it was essential to try to visualize the ovaries in this particularly young patient.
CT and MRI are performed for further evaluation. On CT, myxoid liposarcomas appear on unenhanced images to have signal characteristics close to those of water. With contrast administration, there is little enhancement [8].
MRI is important for evaluating the extent of the tumor and further helps characterize its nature. It shows a spectrum of appearances depending on the amount of fat and myxoid material, the degree of cellularity and vascularity, and the presence of necrosis [1, 8]. The appearance of the mass on contrast-enhanced T1 images could be classified into one of three groups: homogeneous, heterogeneous, or no enhancement, depending on the combination of the histology subtype [9, 10].
In our patient, MRI showed the tumor as being the heterogeneous type. A low-signalintensity mass was seen on the T1 images. On T2 images, a high-signal-intensity heterogeneous mass that had an amorphous and lacy appearance was seen. With gadolinium administration, the mass mildly enhanced heterogeneously to show increased cellularity and vascularity within the tumor. On T2, myxoid liposarcomas, well-differentiated liposarcomas, and lipomas typically show high signal intensity relative to the amount of fat within them. Myxoid liposarcomas contain a low fat content [1]. T2-weighted imaging with fat saturation may help to differentiate between the different entities [3-5].
In conclusion, large retroperitoneal tumors, especially those of the myxoid type, should be imaged in detail to enable proper diagnosis, surgical planning, and patient preparation and positioning for surgery. It would have been unwise to skip preoperative imaging in our patient because without the information provided on imaging, the patient's chances for successful curative surgery might have been compromised.
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This article has been cited by other articles:
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  E. S. Siegelman Myxoid Sarcoma Versus Aggressive Angiomyxoma Am. J. Roentgenol., December 1, 2007; 189(6): W382 - W382. [Full Text] [PDF]
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O. Benjaminov, S. Fichman, and H. Gutman Reply Am. J. Roentgenol., December 1, 2007; 189(6): W383 - W383. [Full Text] [PDF]
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