A 77-year-old man, with no toxic habits, with a personal history of allergy to iodinated contrast, prostate adenocarcinoma with vertebral metastasis in 1998, treated with radiotherapy and hormone therapy. Arterial hypertension, hypercholesterolemia, ischaemic heart disease, repeated nephritic colic and intention tremor.
In the computerised axial tomography (CAT) scan to monitor his prostate pathology, a right parspinal mass was detected. A biopsy revealed the presence of a myxoid soft tissue sarcoma, 16 x 6 cm in diameter, extending from T12 to L3, without infiltration of subcutaneous tissue.
The patient was operated on by the Traumatology and Orthopaedics Department in conjunction with the Plastic Surgery Department, performing en bloc exeresis of the erector spinae muscle compartment affected, leaving a residual defect as shown in Fig. 1. The tumour did not microscopically affect the skin or subcutaneous tissue. Preoperative imaging tests also suggested that the tumour respected superficial planes, so we opted for the placement of a rectangular tissue expander, 20 x 7 cm in diameter, model SRV2007 (Allergan®, Irvine, California, USA), 750 cc in volume. The closure was made in planes (subcutaneous cellular tissue and skin). We tunneled the reservoir to fill the expander in a subcutaneous plane, cranially and laterally to its final location in the right axillary midline.

Intraoperative filling of the expander with physiological saline until the skin was brought into plane with respect to the adjacent regions, with a total of 680 cc.

Perioperative antibiotic prophylaxis was carried out with intravenous cefuroxime, then maintained for 5 days in the postoperative period, which was uneventful except for postoperative anaemia in the immediate phase, which required transfusion of 2 red blood cell concentrates. Hospitalisation lasted 20 days, and the patient was able to ambulate independently on discharge, with support from a brace as the only orthopaedic measure.
After the operation, the Orthopaedic Service carried out periodic follow-ups, with no back pain, scoliosis or neurological deficits being observed during the first 10 months. We also carried out weekly check-ups in the Plastic Surgery outpatient clinic until 2 months after surgery, then once a month for 3 months, and then every 3 months thereafter. We were able to verify a good quality of the scar, without significant functional deficits. There was no extrusion of the expander, and the imaging tests showed no migration or volume depletion of the expander. The control X-rays 4 months after surgery showed minimal right lumbar convexity, without clinical repercussions, with excellent functional recovery of the patient and a good aesthetic result, without any depression in the resection area.

The anatomopathological study reported the resected tumour as a low-grade neural sheath sarcoma, with incomplete resection of the deep border.
We decided, in a joint session of the Tumour Committee of our hospital centre, not to carry out a surgical reintervention given the patient's age and, above all, his general condition and previous pathologies. We indicated the follow-up of periodic controls by means of magnetic resonance imaging (MRI) and serial CT scans.

The patient was free of disease for 9 months. Thereafter, we detected local progression of the disease affecting the psoas iliacus and quadratus lumborum muscles, and regional lymphatic dissemination, with poor clinical tolerance to chemotherapy treatment. The patient died of this process 2 years after surgery.

