Primary renal synovial sarcoma presenting with a retroperitoneal bleed

Abstract

Synovial sarcomas are most commonly localised in extremities, especially in the lower thigh and knee areas. Comprising less than 1% of all malignancies, retroperitoneal synovial sarcoma is very rare with primary synovial sarcoma of the kidney being even more infrequent and difficult to diagnose. We describe a case report of a renal synovial sarcoma in a young adult who was initially managed as a case of Wunderlich’s syndrome secondary to what was believed to be a ruptured renal angiomyolipoma. After biopsy confirmation, the patient was eventually managed with neo-adjuvant chemotherapy followed by a right radical nephrectomy and right hepatectomy. Despite its rarity, synovial sarcoma should be considered as differential diagnosis of a bleeding retroperitoneal soft tissue mass detected in young adults.

Background

Primary renal synovial sarcoma is a rare tumour, first described by Argani et al in 1999. ¹ Current literature suggests that these tumours grow slowly and mimic benign lumps.² Soft tissue sarcomas are rare and comprise only 1% of all malignancies, of which those of retroperitoneal origin only make up 10%.³

The most common types of retroperitoneal sarcomas are liposarcomas, leiomyosarcomas and malignant fibrous histiocytomas. Synovial sarcomas, however, only constitute 8%–10% of all sarcomas.³ The term synovial sarcoma refers to the morphology that resembles developing synovium. While majority of these already rare cases occur in extremities near the large joints, only 5%–15% affect the head and neck, mediastinum, abdominal wall and retroperitoneum.⁴ Thus, the notion of a renal primary retroperitoneal synovial sarcoma is extremely rare. We aim to demonstrate that despite its rarity, synovial sarcoma should be included in the differential diagnosis of a retroperitoneal soft issue mass in a young adult.

Case presentation

We present a case of a 21-year-old man with no medical history who presented to the emergency department with abdominal bloating and visible haematuria. On examination, his abdomen was distended, with a palpable right flank mass. A CT abdomen and pelvis was performed and a heterogeneous septated mass was found in the right abdomen arising from the upper right kidney measuring 19×16×30 cm³ (figure 1). There was a large amount of intralesional haemorrhage. A dedicated CT urogram further characterised the lesion as a large renal mass with a mixed-age haematoma and possible angiomyolipoma (AML). He was managed as having a bleeding AML and underwent angioembolisation of the branches supplying it. The patient was haemodynamically stable and was discharged soon after. An interval CT repeated approximately a month after the embolisation noted the bulk of the mass being hypodense and extending into the right renal collecting system causing moderate hydronephrosis.

Figure 1.

CT performed at presentation showing a heterogeneous mass originating from the right kidney with haemorrhagic components.

Investigations

After discussion in an institutional radiology meeting, an MRI was suggested for further characterisation of the lesion and demonstrated a right abdominal mass with enhancing solid-cystic components involving the right kidney with no discernible fat plane with the adjacent right liver lobe invasion. A renal biopsy was arranged and histology revealed a spindle cell tumour consistent with synovial sarcoma.

Treatment

Given the histology, the case was discussed at a multidisciplinary tumour board meeting and decision was made for neoadjuvant chemotherapy followed by surgery. The patient received six cycles of doxorubicin (Adriamycin) and ifosfamide (Ifex) over 4 months (with a cumulative doxorubicin dose of 415 mg/m²) with post-chemotherapy scans (figure 2) showing interval decrease in size of the mass. Based on the Response Evaluation Criteria in Solid Tumours, there was a partial response. Thus, neoadjuvant chemotherapy here was essential in down-staging the tumour and making it surgically resectable. The patient then underwent a right radical nephrectomy and right hemi-hepatectomy 1 month after completing his chemotherapy. The cardio-thoracic surgeons were also on standby for this case should there be a need for cardio-pulmonary bypass when controlling for the supra hepatic great vessels.

Figure 2.

CT performed post chemotherapy showing an interval decrease in size of the right renal mass.

The open approach via a subcostal chevron incision with sternal extension was used to allow for maximal exposure. Intraoperatively, no peritoneal disease was noted but there was invasion of tumour into the right hepatic lobe. Accordingly, our hepatobiliary colleagues assisted with an extended right hemi-hepatectomy. The approximated intraoperative blood loss was 200 mL. Postoperatively, the patient was observed in a high-dependency unit for 3 days. Patient required a single unit (500 mL) of blood transfusion postoperatively when a haemoglobin drop was noted from 9.4 g/dL to 8.1 g/dL. Apart from a right 2.5 cm hydropneumothorax that was managed conservatively as the patient was asymptomatic, there were no significant postoperative complications. Wound pain was well controlled using a Braun ON-Q PainBuster which was inserted subfascially. By postoperative day (POD) 3, the patient was progressed to feeds and gradually to soft diet by POD 5. The patient was discharged on POD 5.

Histopathological analysis of the nephrectomy specimen confirmed a 19×16×10 cm³ pT3 FNCLCC (French Federation of Cancer Centers Sarcoma Group) Grade 3 synovial sarcoma with invasion of the adjacent liver parenchyma (figure 3). Immunohistochemistry studies noted that the tumour was positive for CD56, TLE1 and BCL2.

Figure 3.

Nephrectomy and right hepatectomy gross specimen.

Outcome and follow-up

The case was discussed to determine the postoperative management given the histology, and the decision was made for adjuvant chemotherapy with ifosfamide alone (as lifelong dosage of doxorubicin was almost reached). The patient however opted to hold off adjuvant therapy.

A CT thorax abdomen and pelvis was performed 3 months postoperatively and confirmed that there was no local recurrence at the surgical bed and no features of lymphadenopathy or distant metastasis.

Discussion

A primary retroperitoneal sarcoma has been defined as a tumour in the retroperitoneal space, with an origin of mesodermal structures such as bony, renal, visceral, adrenal, and pancreatic tissues.⁵

Primary renal sarcomas make up only 1% of malignant renal tumours.⁶ Leiomyosarcoma is the most frequent type comprising 40%–60%, followed by rhabdomyosarcoma, chrondrosarcoma, osteosarcoma and angiosarcoma. It affects young individuals between 20 and 50 years old.

Synovial sarcoma is subclassified into biphasic, monophasic, spindle cell and poorly differentiated types.⁶ The poorly differentiated variants comprise 20% of cases, have the poorest prognosis and in turn, have three histologic variants: large cell, small cell and high-grade spindle cell variants.

Correct diagnosis is crucial as these tumours are associated with an aggressive behaviour and metastasise with less favourable outcomes. The diagnosis is difficult due to the rarity of the tumour and its similar presentation compared with other renal tumours. Furthermore, there are no clinical or imaging abnormalities that can indicate the diagnosis. Most of these lesions are found incidentally on radiological investigation.

This patient was initially managed as a bleeding AML. These are common benign renal tumours of the kidney composed of smooth muscle, adipose tissue and blood vessels. Larger lesions can be diagnosed on imaging by the presence of fat within the tumour but difficulty arises when small lesions are indistinguishable from cystic lesions. Another differential would be a renal cell carcinoma presenting as Wunderlich’s syndrome.

To arrive at a diagnosis of renal synovial sarcoma, the possibilities of distant metastasis and secondary retroperitoneal synovial sarcoma must be excluded. Synovial sarcoma should be considered when retroperitoneal soft tissue masses are found in young adults. They do not have specific imaging features differentiating it from other mesenchymal tumours.^7–9

CT is still recommended as the best imaging method for assessing local invasion, for surgical planning and for evaluating tumour repose to ongoing chemoradiotherapy. On CT, these tumours are hypodense and show irregular enhancement in the periphery with poor enhancement in the central area reflecting reactive, cystic and haemorrhagic changes.⁴ A heterogeneous mass with non-specific features may also be seen on MRI, with signal intensity similar to that of skeletal muscle on T1-weighted images.

In general, there are no clinical or imaging characteristics that confirm definite preoperative diagnosis. This requires histopathological confirmation. Histologically, primary renal synovial sarcomas consist of plump spindle cells with minimal cytoplasm, active mitotic figures and tubular cells.¹⁰ Immunohistochemistry studies however can confirm the pathological diagnosis. In the present case, staining was positive for CD56, TLE1 and BCL2. Synovial sarcomas usually stain positive not only for BCL2 and CD56 but also for CD99/Mic2, Vim, and focally for epithelial membrane antigen.¹¹ Reverse transcriptase-polymerase chain reaction analysis can also assist in diagnostic confirmation of synovial sarcoma. Specifically, there is a chromosomal translocation t(X;18)(p11.2;q11.2) that causes fusion of the SYT gene on chromosome 18 with the SSX family gene on chromosome X.⁶

There are no clear guidelines for the management of primary renal synovial sarcomas due to its extreme rarity.¹² Although primary surgical resection is the treatment of choice, the prognosis is poor with this treatment alone. Synovial sarcomas may be sensitive to high-dose isophosphamide-based and adenomycin-based regimens.^{13 14} Our patient showed good response with neoadjuvant therapy, aiding in reduction of tumour burden prior to surgery.

Learning points.

• In young patients presenting with retroperitoneal bleeding, causality should not be dismissed as an angiomyolipoma. Other more sinister pathologies such as renal cell carcinoma presenting as Wunderlich’s syndrome, or sarcomas, should also be considered.

• After undergoing emergency management such as angioembolisation, patient’s with retroperitoneal haematomas should be followed-up with interval CT scans to exclude the presence of malignant soft tissue lesions.

• Synovial sarcomas are responsive to isophosphamide-based and adenomycin-based chemotherapy regimens.

• Surgical and postoperative care for renal synovial sarcoma requires a multidisciplinary team comprising urologists, hepatobiliary surgeons, cardiothoracic surgeons (to stand-by), medical oncologists, intensive care staff and pain management teams.