Patient aged 86 years, retired construction worker, with no previous medical or surgical history, who consulted for occasional episodes of dizziness.

Physical examination revealed an irregular pulse rate of 92 per minute, blood pressure of 110 / 80, normal cardio-pulmonary examination and a BMI (Body Mass Index) of 26. Abdominal examination revealed a painless mass in the right flank, which moved with respiratory movements.

Preoperative evaluation shows an electrocardiogram with a complete arrhythmia due to atrial fibrillation, normal haemogram with a sedimentation rate of 36 mm/hr, Creatinine of 1.03 mg/dl, normal albumin and total protein, and normal liver function. A CT scan of the abdomen showed a multilocular cystic mass 12 cm in diameter in the lower pole of the right kidney.

With the diagnosis of a right renal tumour, the risks of surgery were discussed with the patient and family, who agreed to the procedure. Three weeks after diagnosis, a laparoscopic hand-assisted radical nephrectomy was performed, indicated by the size of the tumour mass.

The surgical procedure was performed with the placement of 4 trocars. Two 10 mm trocars, one right subcostal and one right pararectal at the level of the umbilicus, the latter for insertion of the camera. Two 5 mm trocars are also placed in the epigastrium to separate the liver. The surgeon's hand is introduced through an oblique incision in the right iliac fossa. Radical nephrectomy is performed in the usual way preserving the adrenal gland. The kidney is placed in a polyethylene bag and removed through the iliac fossa incision.

Surgical time was 100 minutes, with estimated bleeding of less than 100 ml. There were no intraoperative or postoperative haemodynamic alterations.

The immediate postoperative period evolved without complications, requiring non-steroidal analgesics (Ketorolac) for pain control. Medical discharge was indicated 36 hours after surgery.

In the outpatient control 9 days after surgery the patient was asymptomatic and his tests showed a haemoglobin of 13.7 mg/dl, creatinine of 1.74 mg/dl and urea nitrogen of 23.0 mg/dl.

The biopsy was reported as kidney and perirenal adipose tissue which together weighed 1,400 g. Towards the lower pole and in intimate contact with the kidney there was a 9.5 cm tumour, firm in consistency, which on section showed extensive cystic areas, yellow-orange, softened, necrotic, with haemorrhagic content and which did not penetrate the renal capsule. On the periphery of the tumour there were well-defined, pale yellow, adipose-like tumour areas, which together constituted a tumour measuring 15 cm in diameter and which were in close contact with the surgical section, separated from it by a thin sheet of fibrous tissue 0.1 cm thick.

On histological examination the renal parenchyma showed preserved architecture. The central tumoural portion showed a hypercellular neoplastic proliferation of spindle-shaped, stellate, epitheloid cells, some giant, with scanty, poorly demarcated cytoplasm, irregular nuclei with prominent nucleoli and high mitotic rate; the cells were arranged in sheets amidst a moderately abundant myxoid stroma in some areas with G3 myxofibrosarcoma (myxoid variant malignant fibrohistiocytoma).

In the peripheral portions, the tumour had a clearly better differentiated adipose appearance with G1-2 myxoliposarcoma features. The adipose tumour was separated from the surgical section by a thin sheet of fibrous tissue 1 mm thick.

The pathology report concluded that it was a perirenal myxoliposarcoma with indifferentiation towards a G3 myxofibrosarcoma (malignant fibrohistiocytoma myxoid variant). The patient is currently asymptomatic and with stable renal function 9 months after surgery.