Leiomyosarcoma of the azygos vein. An unusual case

Soft tissue sarcomas (STS) are a heterogeneous and rare group of malignant tumours of mesenchymal origin. They account for 1% of all malignant neoplasms¹ and the most common of these is leiomyosarcoma². This lesion is made up of smooth muscle differentiation cells¹ and accounts for 20% of all sarcomas².

We present the case of a 63-year-old woman who was followed up for dorsalgia and underwent MRI of the dorsal spine showing a solid tumour measuring 4.4 × 4.0 × 2.4 cm. Circumscribed in the right paravertebral posterior mediastinum at the level of T7-T8 with no relation to the foramen conjunctiva (Fig. 1A). To complete the study, digestive endoscopy was performed, which excluded mucosal alteration of the oesophagus at this level, and a CT-guided biopsy with a coarse needle biopsy, which diagnosed the tumour as a low-grade leiomyosarcoma. Its origin was the azygos vein and its location was assessed on CT (Fig. 1B), which was subsequently confirmed by tumour resection.

Fig. 1.

Radiologic tumour findings:

A) Contrast-enhanced MRI of the dorsal spine, axial and sagittal view: well-defined solid tumour (white arrow) in the right posterior paravertebral mediastinum at T7-T8 level, unrelated to foramen conjunctiva, causing slight remodelling of the anterior vertebral margin, without bone invasion.

B) Axial computed tomography image, mediastinal window: oval solid tumour in posterior mediastinum (white arrow).

Surgery was performed by right thoracotomy through the 5th intercostal space with preservation of the serratus anterior muscle.

The intraoperative view showed a hard, encapsulated, highly vascularised tumour with nutrition from the azygos vein and intercostal arteries, extending from the lower edge of the azygos vein arch, continuing longitudinally adjacent to the oesophagus and vertebral bodies as well as the junction of the transverse processes of the costal arches 5,6 and 7 (Fig. 2A).

Fig. 2.

Macroscopic view and anatomopathological study.

A) Intraoperative view: hard tumour (black arrow), encapsulated, highly vascularised with nutrition from the azygos vein (white arrow).

B) Solid tumour measuring 4 × 3 cm, with an elastic consistency.

C) Microscopic study shows a malignant mesenchymal proliferation of spindle cells with fibrillary cytoplasm, blunt edges, long-linear nuclei, and others with a bizarre appearance (haematoxylin-eosin, 20×).

D) A tumour immunophenotype of muscular origin is observed, with diffuse expression of the immunohistochemical marker Desmin (20×).

To excise the tumour, dissection of the parietal and mediastinal pleura limiting the tumour was carried out, identifying the longitudinal edge with respect to the oesophagus, which respected it, as well as the vertebral bodies and transverse processes, intimately adherent but without macroscopic tumour infiltration. Dissection of the azygos vein in contact with the tumour was completed, requiring sectioning and mechanical vascular suturing, finally achieving en bloc tumour excision with the affected vein (Fig. 2B). Finally, the edges of the surgical site were marked with clips. No pathological lymphadenopathies were visualised.

The anatomopathological study confirmed the origin of the azygos vein as a grade 2 leiomyosarcoma (according to FNCLCC) with focal involvement of the soft tissue resection margin.

To complete the treatment, the clinical case was discussed at the Multidisciplinary Committee for Thoracic Tumours and the patient was referred to Radiation Oncology, receiving a total of 33 sessions on the surgical bed, with good tolerance. After this, the patient continued clinical radiological follow-up, with no evidence of tumour recurrence to date.

Leiomyosarcomas can originate in any vessel, being an extremely rare origin, accounting for <2% of all leiomyosarcomas, affecting up to 5 times more arteries than veins³.

The most common venous origin is the inferior vena cava, which accounts for 50% of all venous leiomyosarcomas, with a total of 450 described in the literature⁴.

Our case is frankly unusual due to the very low frequency of origin in the azygos vein, as to date only 2 cases have been described in the literature^5,6. The first case was described in 1995 by Levett⁵, it was a leiomyosarcoma with origin in the superior vena cava and azygos vein, and after resection it was necessary to replace it with a superior vena cava graft. The second case was described by Dasika in 1998⁶, reporting a leiomyosarcoma of the azygos vein that was excised by previously ligating the azygos vein both proximally and distally, without the need for reconstruction.

Given the rarity of this tumour, the best results are obtained with a multidisciplinary approach with teams experienced in the management of these tumours.