Incidental Finding of Renal Cell Carcinoma in Recurrent Retroperitoneal Liposarcoma

Abstract

This is the first reported case of concomitant renal cell carcinoma with retroperitoneal liposarcoma (also involving the kidney). It highlights the speed and aggression of liposarcoma recurrence and re-inforces the need for complete resection margins when excising liposarcomas.

A 79-year-old man presented with 2-day profuse watery diarrhoea and a 6 kg weight loss over 2 months. He was otherwise well with no relevant past history. Physical examination was normal as were his initial haematological tests (thyroid function, urea and electrolytes, liver function, CRP and full blood count).

CT pneumocolon revealed a large retroperitoneal soft tissue mass (16 × 13 × 9 cm) causing anterior distortion of the duodenojejunal junction, splenic vessels and pancreas. A clear tissue plane was seen between the mass and the adjacent pancreatic tissue and duodenum but there was some retroperitoneal fat stranding around the left kidney and psoas muscle. The differential diagnosis included gastrointestinal stromal tumour and retroperitoneal sarcoma.

Laparotomy confirmed a firm retroperitoneal tumour on the left side of the abdomen, separate from the spleen and left kidney. It resembled a liposarcoma. The tumour was excised intact along with some retroperitoneal fat; it was covered by a fibrous layer and had areas of necrosis within it. Histology confirmed a sclerosing, well-differentiated liposarcoma that had been narrowly excised and was surrounded by a compressed rim of connective tissue.

The patient remained well postoperatively, although a follow-up CT scan at 3 months revealed a 5 × 4 cm mass posterior to the splenic artery and medial to the left kidney. Although the lesion was likely to represent early tumour recurrence, the patient declined re-operation at first. However, by 16 months postoperatively, he was complaining of abdominal distension and pain and there was a tender mass. Repeat CT showed progression of disease, with a retroperitoneal mass now measuring 16 × 11 × 5 cm. There was marked lateral displacement of the left kidney and considerable stretching of the main renal artery. A second, poorly defined mass, measuring 20 cm in maximal diameter, was also seen extending into the pelvis.

Re-operation revealed a large retroperitoneal liposarcoma encasing the splenic artery and tail of pancreas, with extensive involvement of the kidney and ureteric invasion. The main lesion was excised with nephrectomy and removal of another two ill-defined masses extending down into the pelvis. Histological examination showed three well-differentiated (sclerosing) liposarcomas measuring 40 cm, 20 cm and 14 cm in maximal diameter; each had areas of pleomorphism and necrosis, and the margins were clear. The renal hilum had been replaced by liposarcoma, and invasion of the proximal ureter was confirmed. Further examination of the kidney revealed a 5.5 mm papillary renal cell carcinoma (renal cell carcinoma), which was staged at 1a (T1a, N0, M0).

Figure 1.

A 16-month abdominal CT showing large left liposarcoma recurrence with displacement of left kidney (at level of coeliac axis)

Discussion

This is the only reported case of concomitant renal cell carcinoma with retroperitoneal liposarcoma (also involving the kidney). It highlights the speed and aggression of liposarcoma recurrence and reinforces the need for complete resection margins when excising liposarcomas.

Liposarcomas account for 1% of all malignant tumours and renal cell carcinomas for 3%.^1,2 Between 10–20% of liposarcomas are located within the retroperitoneum, where symptoms arise from involvement of abdominal organs or pressure effects.^1,3 Complete operative resection is the mainstay of treatment, but this can be difficult due to both the size of the tumour and the involvement of other organs.^1,3 CT often reveals organ displacement, but actual infiltration of the kidney is very uncommon (though there may be encasement).¹ Survival rates without resection are poor, and debulking of these tumours seldom improves outcome.^1,3 Despite clear resection margins, there is a high recurrence rate.³

The treatment for stage 1a renal cell carcinoma (i.e. measuring < 4 cm in diameter and confined to the kidney) is nephrectomy, which gives a 5-year survival rate of 97% in patients with incidental disease.^2,4 Incidental renal cell carcinomas are being detected more frequently and at an earlier stage due to the more frequent use of abdominal imaging and its improved quality.⁴

The prognosis for this patient is guarded; the nephrectomy is likely to have cured the incidental renal cell carcinoma, but there is clearly a chance of further recurrent liposarcoma.^1,3 A nephrectomy at the original operation could potentially have prevented the initial recurrence, but the kidney was not involved at that stage and negative resection margins were obtained. Organ resection per se at repeat operation is less frequently indicated for recurrence, unless the original operation was incomplete; in this patient, nephrectomy was performed primarily because the kidney had become directly involved.³ Regular postoperative CT should probably be reserved for patients who become symptomatic, because detection of recurrence is not necessarily an indication for re-operation.^1,3

Although we have found no previous evidence of incidental renal cell carcinoma being discovered during treatment for liposarcoma, there is one report of the reverse situation. In 1994, a liposarcoma was incidentally detected during the treatment for a renal cell carcinoma.⁵ A radical nephrectomy was performed for a T2 N0 M0 renal cell carcinoma; at operation, grossly fatty and haemorrhagic tissue masses within the perirenal fat were found to contain well-differentiated liposarcoma with extramedullary haematopoiesis.⁵ The scarcity of the association argues against a relationship between retroperitoneal liposarcoma and renal cell carcinoma.