In general, retroperitoneal soft-tissue sarcomas are relatively rare and the radiological diagnosis is often difficult. Most are malignant and frequently invade.
The British Journal of Radiology, 78 (2005), 166–169 DOI: 10.1259/bjr/67990800
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2005 The British Institute of Radiology
Case report
Radiological findings of primary retroperitoneal synovial sarcoma 1
S ULUSAN, MD, 1O KIZILKILIC, MD, 1T YILDIRIM, MD, 1C HURCAN, MD, 2N BAL, MD and T Z NURSAL, MD
3 1
Department of Radiology, 2Department of Pathology and 3Department of Surgery, Baskent University Adana Teaching and Medical Research Center, Dadaloglu Mah Serinevler Adana-Turkey
Abstract. Synovial sarcomas are most commonly localized in the extremities, especially the lower thigh and knee areas. Retroperitoneal synovial sarcoma is very rare. We describe the radiological and pathological findings of an adult retroperitoneal synovial sarcoma.
Case report
MRI confirmed the retroperitoneal mass to have higher signal intensity than that of skeletal muscle on spin-echo T1 weighted image (WI) (repetition time (TR) 144 ms, echo time (TE) 4.1 ms) moderately higher signal than that of skeletal muscle on turbo-spin-echo T2WI (TR 5700 ms, TE 120 ms) (Figure 3a,b), and after administration of gadolinium contrast medium (0.1 ml kg21 bw) T1WI (TR 144 ms, TE 4.1 ms) showed marked, homogeneous enhancement (Figure 3c). A phaeochromocytoma was excluded by the absence of hypertension, cardiac arrhythmias, and normal serum and urine levels of catecholamine and vanillylmandelic acid and metanephrine. At surgery, invasion of the inferior vena cava and compression of the right ureter by the mass was seen. Complete resection of the tumour was performed, with repair of the inferior vena cava. In the post operative period, bilateral lower extremity venous thrombosis developed and was treated medically. Post-operatively, the patient received adjuvant chemotherapy.
A 38-year old man was admitted to hospital complaining of bilateral paresis in his feet, weight loss and nonspecific pain of the upper abdomen. Physical examination revealed a palpable right sided upper abdominal mass. The results of routine blood and urine chemical analysis were within normal limits. Abdominal ultrasound (US) demonstrated a welldefined hypoechoic mass with a diameter of 8 cm anterior to the inferior vena cava. Colour Doppler US of the retroperitoneal mass showed uniform hypovascularity. The mass was encircled by the vessels and gave off centripetal branches that passed into the parenchyma of the lesion (Figure 1). CT demonstrated a large spherical, well-defined soft tissue 8 cm mass containing punctate calcification in the right retroperitoneal region. The mass compressed the psoas muscle, inferior vena cava and right ureter resulting in a minor hydroureteronephrosis (Figure 2a). There was marked homogeneous enhancement of the mass post intravenous contrast (Figure 2b).
Figure 1. Abdominal Doppler ultrasound image shows a
Received 15 March 2004 and in final form 10 August 2004, accepted 11 November 2004.
hypoechoic and hypovascular mass (thick open arrow) anterior to the inferior vena cava, encircled by the vessels. The common iliac arteries are seen medial to the mass (thin arrow).
In general, retroperitoneal soft-tissue sarcomas are relatively rare and the radiological diagnosis is often difficult. Most are malignant and frequently invade contiguous retroperitoneal organs. Surgical resection is often difficult or impossible. Retroperitoneal synovial sarcomas do not have specific imaging features differentiating it from other mesenchymal tumours. Despite the rarity of mesenchymal tumours of the retroperitoneum, synovial sarcoma should be included in the differential diagnosis of a retroperitoneal soft tissue mass detected in adults. In this report, we present the radiological and pathological findings of an adult case of retroperitoneal synovial sarcoma examination. Although there a few papers describing the surgical and pathological features, this is the first report specifically addressing the imaging features.
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Case report: Primary retroperitoneal synovial sarcoma
(a)
(b)
Figure 2. (a) Non-contrast enhanced abdominal CT image shows a large spherical, well defined soft tissue mass (small open arrow) and punctuate calcification (arrow) and the psoas muscle behind the mass (big open arrow). (b) Post-contrast CT image demonstrates marked and homogeneous enhancement of the mass (open arrow), right common iliac artery just medial to the mass (thin arrow) and psoas muscle position to the mass (arrowhead).
On microscopic examination the tumour was well demarcated. The tumour cells were large, oval, with large round hyperchromatic nuclei and eosinophilic cytoplasm, and had marked nuclear pleomorphism. Bizarre and multinuclear giant cells and stromal lymphocytes were seen. Immunohistochemically epithelial membrane antigen (EMA), (Dako, N 1504, E29) was diffusely positive and S-100 (Doka, N1519) was focally positive. Leukocyte common antigen (LCA) (Neomarkers, CD 45 Ab-3, Mause, Mab, MS-413-R7, 413R301) was positive in lymphocytes and Desmin, HMB-45, CD 20, CD 34, CD99 were negative. The histological and immunohistochemical findings described the tumour as a synovial sarcoma of the monophasic pattern (Figure 4).
Discussion Synovial sarcoma is a well-recognized soft-tissue malignancy that typically arises in young adults. It is a relatively common primary soft tissue sarcoma and accounts for approximately 5–10% of all malignant mesenchymal neoplasms [1, 2]. The majority (80–95%) of synovial sarcomas occur in the extremities, with approximately 60–70% in the lower limbs [1, 3, 4]. It is the most common malignancy of the foot and ankle in patients aged between 6 years and 45 years old and the most common malignancy of the lower extremity between the ages of 6 years and 35 years [2]. Other rare sites of involvement include the neck, pharynx, larynx, precoccygeal and paravertebral regions, thoracic and abdominal wall, and heart [1, 5]. The retroperitoneal region is a most uncommon place of occurrence. In 1954, Pack and Tabah [6] reported the first retroperitoneal synovial sarcoma. Since then 18 cases have been described. Synovial sarcomas derived from extremities occur more often in males and young adults [7], and the average age of retroperitoneal synovial sarcomas is similar. However, it occurs with an approximately equal sex distribution [7–10]. Since the retroperitoneal space is highly expandable and deeply hidden, early detection of The British Journal of Radiology, February 2005
retroperitoneal synovial sarcoma is difficult. The tumour has no special imaging features that distinguish it from other abdominal and retroperitoneal tumours [7]. We considered phaeochromocytoma in the differential diagnosis, as the radiological findings of phaeochromocytoma are those of hypervascular neoplasms that may show central necrosis, and the mass detected in our patient was hypovascular and contained punctuate calcification. Although the presence of calcification is uncommon in phaeochromocytoma, when present, it may have an eggshell pattern [8]. Our patients’ biochemical findings were not suggestive of a phaeochromocytoma. Although the diagnosis of a retroperitoneal synovial sarcoma is based on the pathological characteristics of the specimen obtained by needle or surgical resection [7], radiographic studies suggest pre-operative diagnosis of synovial sarcoma. CT may identify soft tissue calcifications [11], especially those that are subtle or are located in areas where the anatomy is complex. It may also show areas of haemorrhage, necrosis, or cyst formation within the tumour [12]. CT defines the mass, and readily confirms bone involvement [11, 12]. Intravenous contrast may help in differentiating the mass from the adjacent muscle and neurovascular complex [11, 12]. On MRI, the findings are of a lesion that is usually a non-specific heterogeneous mass with signal intensity approximately equal to that of skeletal muscle on T1W and higher than that of subcutaneous fat on T2W MR images [13, 14]. Signal intensity changes compatible with previous haemorrhage and fluid–fluid levels have been reported [4, 13, 15]. The soft tissue calcifications frequently seen on radiographs and CT may not be detected on MRI [13, 14] although larger calcifications may be identified as areas of decreased signal intensity on all pulse sequences. Scintigraphy may be normal or may show significantly increased uptake of 99Tcm methylene diphosphonate due to mineralization within the tumour which may not be apparent on radiographs [16, 17]. Metastases or local recurrence is seen in approximately 80% of patients [18]. Metastases are present at the time of 167
S Ulusan, O Kizilkilic, T Yildirim et al
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(b)
Figure 3. (a) Pre-contrast T1 weighted sagittal MR image
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shows the retroperitoneal mass which is slightly hyperintense to adjacent muscle (arrows). (b) Axial T2 weighted MR image demonstrates slight hyperintensity of the mass (large open arrow) compared with muscle (small open arrow). (c) Post gadolinium T1 weighted image shows homogeneous enhancement of the lesion (large open arrows) compared with psoas muscle adjacent to the mass (small open arrow).
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Case report: Primary retroperitoneal synovial sarcoma
Figure 4. Pathological section of the tumour showing tumour cells consisting of oval, rounded cells with hyperchromatic nuclei and eosinophilic cytoplasms (haematoxylin and eosin (HE)6100), with high power inset (HE6400).
initial diagnosis in about one quarter of patients [18] but have been reported with a latency of 35 years following initial diagnosis [1]. Metastases may be to multiple sites but are predominantly pulmonary [4, 18, 19]. Local recurrence is frequent, occurring in the excision scar or the amputation stump, often within 2 years of the initial presentation.
Conclusions Synovial sarcomas can be classified into four histopathological types: (1) biphasic; (2) monophasic fibrous; (3) monophasic epithelial; and (4) poorly differentiated. Immunohistochemistry is helpful in differential diagnosis. This case was confirmed to be a synovial sarcoma of monophasic epithelial type based on its immunohistochemical features. Primary retroperitoneal sarcomas may be biphasic as well as monophasic. Monophasic synovial sarcomas behave more aggressively and metastasize earlier then do biphasic tumours [20, 21]. No imaging differences have been reported between the monophasic and biphasic variants [22]. To our knowledge, this is the first case of primary retroperitoneal synovial sarcoma, reported with CT, MRI and colour Doppler ultrasound findings.
References
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