A 69-year-old man came to us for a check-up for prostatic syndrome in treatment with an alpha-blocker. He had undergone surgery on the right hip, hypoacusis and repeated angina. He had an episode of left costolumbar trauma some 30 years ago. Urological history of haematuria on two occasions, the last time a year ago.

On examination, the prostate had fibroadenomatous characteristics, volume II/IV, with no nodulation. On abdominal palpation, there was a large mass located in the left hypochondrium and left void, painful on palpation.

Laboratory tests: Hb 14.6 g/dl, Hcto. 43.1%, ESR 9 mm/h and biochemistry within normal limits. PSA: 3.1 ng/ml.

Simple X-ray: large mass effect located in the left hypochondrium and left void, ovoid in shape, totally calcified.

In view of these findings, a differential diagnosis with any mass located in the retroperitoneum with this type of calcification is considered:

- Primitive retroperitoneal tumours

- Adrenal tumours

- Renal tumours

- Metastatic tumours

- Infectious pathology

Blood determinations of plasma renin activity before and after ambulation, as well as aldosterone and cortisol at 8 and 20 hours are performed, the results being within normal range. Urine levels of 17-ketosteroids and corticosteroids, as well as catecholamines, metanephrines and vanillylmandelate were normal. All of the above ruled out a functioning adrenal tumour.

Stains for acid fast bacilli in urine and sputum were also negative, as was the Mantoux test.

The possibility of a calcified hydatid cyst was raised, but serology was negative. The previously suffered left costolumbar trauma was also considered as a possible cause of the calcified adrenal mass.

With the diagnosis of a retroperitoneal mass without filiation, exploratory laparotomy was performed, finding a protruding lesion in the left hypochondrium, hard to palpation, with fixation to deep planes and diffuse lesions distributed throughout the peritoneum, with the intraoperative anatomopathological report of peritoneal fat infiltrated by a malignant tumour of probable mesenchymal origin. It was decided to close the abdominal cavity as it was a disseminated malignant process. The definitive pathological report was pleomorphic liposarcoma, with immunohistochemical techniques of: S100: positive; Oil-Red: positive; vimentin: positive; PS 3: positive; desmin: negative.

The patient was discharged on the seventh day after the operation and died two weeks later at home.