CASE 13612 Published on 08.05.2016

Primary synovial-sarcoma of the kidney

Section

Uroradiology & genital male imaging

Case Type

Clinical Cases

Authors

Tonolini Massimo, M.D.1; Isabella Luigi, M.D.2

"Luigi Sacco" University Hospital,
Radiology1 and Oncology2 Departments
Via G.B. Grassi 74
20157 Milan, Italy
Email:mtonolini@sirm.org
Patient

55 years, male

Categories
Area of Interest Kidney ; Imaging Technique CT
Clinical History
Overweight male with type II diabetes mellitus on metformin therapy, suffering from right abdominal and flank pain. Physical finding of ipsilateral palpable swelling, without peritonism. History included past episode (2 years earlier) of acute renal failure with unremarkable sonographic renal appearance. Currently, laboratory studies including renal function within normal limits.
Imaging Findings
Unenhanced (Fig. 1) and post-contrast (Fig. 2) CT detected a right-sided subcapsular renal haematoma, with associated mild retroperitoneal bloody effusion and a 15 cm well-demarcated roundish exophytic complex mass arising from the kidney. The latter lesion was predominantly hypodense (15-20 Hounsfield units, HU) with thin septa, and contained hyperattenuating (50-60 HU) regions (*) suggesting presence of fresh blood, without enhancing mural nodules. Both kidneys were normally functioning without hydronephrosis.
Under diagnosis of ruptured Bosniak class 3 mass, the patient was treated conservatively and improved clinically. A month later, open nephroureterectomy was performed.
Pathology confirmed a mixed solid, cystic and haemorrhagic brownish mass, diagnosed as malignant mesenchymal proliferation, which spared the resection margin, perirenal fat and collecting system. Immunohistochemical staining including positivity for vimentin and BCL-2 was consistent with synovial sarcoma.
Six months later, follow-up positron-emission tomography (not shown) and CT (Fig. 3) excluded signs of relapse.
Discussion
Synovial-sarcoma (SS) is an uncommon mesenchymal malignancy which accounts for 5-10% of all soft-tissue sarcomas, and typically affects the limbs in the proximity of large joints. Occasionally SS has been reported to arise in unexpected sites including the thoracic-abdominal wall, head and neck, lungs and visceral organs. Primary renal SS (PR-SS) is extremely rare, with 65 cases reported in a recent literature review [1-4].
PR-SS occurs in young or middle-aged people (average age of 38 years) of both genders. Clinical manifestations are similar to those of any renal tumour, such as flank pain, haematuria, and sometimes a palpable mass. Albeit generally large in size (mean diameter 11 cm), at diagnosis PR-SS rarely (10% of patients) has nodal and distant metastases [1-4].
Sonographically, PR-SS appear as large ovoid masses with mixed cystic and solid hypoechoic appearance. Cross-sectional imaging is required for local and distant staging. At CT, PR-SS appear as well-demarcated, mixed solid and multiloculated cystic masses without macroscopic fat, and generally extend in the perinephric space. Contrast enhancement is usually heterogeneous due to intralesional haemorrhage and necrosis. Some tumours are predominantly cystic with enhancing septa and mural nodules. In a few cases, MRI showed PR-SS with intermediate T1- and heterogeneously T2 signal intensity (SI) due to a mixture of low, intermediate, and high SI portions (the so-called “triple sign”) representing haemorrhagic, fluid and necrotic changes [5-7].
Diagnosis of primary renal sarcoma requires exclusion of metastatic involvement from sarcoma in other body regions, of extrarenal retroperitoneal sarcoma, and of sarcomatoid renal cell carcinoma. The diagnosis is established by histopathology, but differentiation from other more common sarcomatoid renal tumours is challenging. Overall, mesenchymal tumours account for less than 2% of all renal malignancies, with leiomyosarcoma as the commonest from (approximately 50% of cases). PR-SS are typically mixed cystic and solid tumours with haemorrhagic and necrotic changes, made up of “plump” mitotically active spindle cells. In most cases, cytogenetic analysis demonstrated a characteristic chromosomal translocation [5, 6].
Radical surgical resection is the mainstay treatment. Compared to other sarcomas, PR-SS show chemosensitivity in 50% of cases. Albeit on a small number of patients, the clinical course is often aggressive, and the prognosis is generally dismal in patients with metastases at presentation or postoperative recurrence. Local or distant relapse is reported in 36% of operated patients [1, 2].
Differential Diagnosis List
Primary renal synovial-sarcoma presenting with subcapsular haematoma
Renal leiomyosarcoma
Clear-cell sarcoma of the kidney
Primitive neuroendocrine tumour of the kidney
Renal liposarcoma / rhabdomyosarcoma / fibrosarcoma
Adult Wilms’ tumour
Sarcomatoid renal cell carcinoma
Primary (extrarenal) retroperitoneal soft-tissue sarcoma
Final Diagnosis
Primary renal synovial-sarcoma presenting with subcapsular haematoma
Case information
URL: https://www.eurorad.org/case/13612
DOI: 10.1594/EURORAD/CASE.13612
ISSN: 1563-4086
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