Primary synovial sarcoma of the lung successfully resected under temporary bypass

Abstract

A 48-year old man presented with chest pain and haemoptysis. Chest computed tomography showed a 60-mm mass in the left upper lobe of the lung, adjacent to the distal aortic arch. Bronchoscopic cytology revealed the presence of malignant cells and, in the absence of evidence of distant metastasis, a thoracotomy was performed. Although the tumour was firmly adherent to the distal aortic arch, under temporary bypass from the left subclavian artery to the descending aorta, it was successfully resected en bloc with the section of the aorta attached to it. The tumour was diagnosed as a primary synovial sarcoma of the lung on the basis of histopathological findings and fluorescent chromogenic in situ hybridization, showing SS18 gene rearrangement.

INTRODUCTION

Primary pulmonary sarcoma is a rare neoplasm, accounting for only 0.1% of primary malignant lung tumours resected in 2010 in Japan [1]. Synovial sarcomas of the lung have recently become more clinically identifiable because of their distinctive chromosomal translocation [2]. We present a case of this type of tumour that was adherent to the distal aortic arch and curatively resected.

CASE REPORT

A 48-year old man presented with chest pain and haemoptysis. Chest computed tomography (CT) showed a smooth-margined, heterogeneously enhanced, 60-mm mass in the left upper lobe of the lung, adjacent to the distal aortic arch (Fig. 1). Bronchoscopy brushing cytology revealed the presence of malignant cells, but it was difficult to identify a specific histological type. Since there was no evidence of distant metastasis, the patient underwent a thoracotomy.

Fig. 1.

CT showing a mass adjacent to the distal aortic arch. The inset shows a reconstructed image of the frontal section.

The tumour was adherent to the distal aortic arch, hampering an approach to the cephalic aspect of the left pulmonary hilum. Therefore, the dissection of hilar structures was carried out from caudad to cephalad. Specifically, we divided the lingular artery, the left upper pulmonary vein, the left upper bronchus and the apicoposterior segmental artery, in that order. At this point, the left upper lobe was adherent only to the aortic arch. Since the adherence was too tight to allow dissection, we resected the aorta in combination with the left upper lobe of the lung after establishing a temporary bypass from the left subclavian artery to the descending aorta (Supplementary video 1). After the aorta was cross-clamped, the portion that was attached to the tumour was resected and the aorta was reconstructed by replacing it with a 24-mm diameter, woven vascular graft in an end-to-end anastomosis. To isolate the bronchial stump and the prosthetic vascular graft, we separately covered the bronchial stump and prosthesis with the pedicled pericardial flap and the dissected parietal pleura (Supplementary video 2). The postoperative course was uneventful and the patient was discharged on postoperative day 11. The patient has remained free of recurrence after 42 months of the follow-up without any adjuvant therapy.

Supplementary Video 1:

Placement of the temporary bypass between the left subclavian artery and the descending aorta.

Supplementary Video 2:

Coverage of the bronchial stump and the prosthesis with pedicled pericardial flap tissue and the dissected parietal pleura. The pedicled tissue was fixed with fibrin glue.

Histopathological examination of the tumour revealed that it was a well-circumscribed, round tumour, 50 × 32 mm in size, which was macroscopically extensively haemorrhagic and necrotic. The tumour cells were spindle-shaped, with a modest mitotic activity (5 mitoses per 10 high-power fields), and forming interlacing fascicles (Fig. 2A). There was no infiltration of the tumour into the aortic wall, and all surgical margins were tumour-free; the lymph nodes were also not involved. Immunohistochemical staining was positive for bcl-20, vimentin and CD99; partially positive for CD56 and synaptophysin; and negative for c-kit, CK34betaE12, CK7, CK20, EMA, thyroid transcription factor-1, alpha-smooth muscle actin, S-100, p63 and HBME-1. The dual-color, break-apart, chromogenic in situ hybridization for detecting SS18 rearrangement showed split signals (Fig. 2B) [3]. On the basis of these findings, the tumour was diagnosed as a monophasic type, synovial sarcoma of the lung.

Fig. 2.

(A) Haematoxylin-eosin stained section showing dense proliferation of spindle cells. Bar indicates 50 µm. The inset shows the cut surface of the resected specimen. Dotted line demarcates the aortic wall. (B) Photograph of the fluorescent in situ hybridization showing multiple fluorescent dots representing SS18 gene rearrangements.

DISCUSSION

Although the definitive diagnostic measures for synovial sarcoma have been established in surgical specimens, preoperative diagnosis of synovial sarcoma by biopsy or cytology remains difficult. The present case was provisionally diagnosed as a lung cancer before surgery. The availability of such limited information on the basis of preoperative specimens might lead to suboptimal treatment options. Therefore, one of the reasons why we chose thoracotomy was the necessity of securing a pathological diagnosis. Moreover, we anticipated that the tumour could be dissected free of the aorta since it demonstrated well-circumscribed margins in the imaging study. Contrary to our preoperative expectations, the rigorous adhesion of the tumour to the aorta forced us to perform a combined resection of the aorta. Although the tumour had not infiltrated the aorta, inflammation due to excessive intratumour haemorrhage and necrosis had increased the strength of the adhesion.

There were two conceivable options for ensuring distal blood flow during the cross-clamping of the aorta. Either percutaneous cardiopulmonary support or a temporary bypass could have been used [4]. The patient's urine output decreased during the cross-clamping, indicating the need to choose a graft >10 mm in diameter. We believe that this procedure is a feasible option that is advantageous to deploy in the same operative field without inguinal surgical skin preparation or limitations of device availability. Since we experienced one other case complicated by chylo-pyothorax without a bronchial fistula after combined left pneumonectomy and aorta resection, we covered bronchial stump and the aortic prosthesis separately with the pedicled tissue to protect against intrathoracic bacterial contamination. This manoeuvre would be efficacious even in a worst-case event, such as a window thoracostomy.

Although the present case has not experienced recurrence without adjuvant therapy, radiotherapy would also be an option [5]. The therapeutic utility of chemotherapy in the adjuvant setting remains unclear. Since complete resection is still the main treatment modality, aggressive combined resection should be considered as far as possible.

SUPPLEMENTARY MATERIAL

Supplementary material is available at ICVTS online.

Conflict of interest: none declared.