Autosomal dominant polycystic kidney disease [APKD] occurs in approximately 1/500 to 1/1000 live births and is present in 10% - 12% of end-stage renal disease patients [1]. It is able, like other genetic diseases, of malignant transformation [2].

Renal cell carcinoma associated with APKD has already been reported in the literature, whereas only few cases of sarcoma have been reported.

We report a case of renal pleomorphic sarcoma in a patient with APKD.

A 42-year-old male, without significant medical history presented with a pain of the left flank associated to constipation without urinary symptoms. Abdominal examination discovered a mass of left flank.

Ultrasonography revealed multiple and bilateral renal cystic masses of which some have heteroechoic content. Enhanced computed tomography [CT] shows bilateral polycystic kidney and a voluminous solid mass in the upper pole of the left kidney with heterogeneous enhancement and large central necrosis (Figure 1).

Abdominal MRI achieved in axial and coronal plans in T2 and T1 weighted sequences before and after gadolinium injection, confirmed the presence of multiple cysts and enhancing masses. These masses presented an isosignal on T1 and low signal on T2. Following intravenous gadolinium injection, the lesions showed intense and heterogeneous enhancement (Figures 2 and 3).

The most voluminous lesion measured 15cm and was located in the upper pole of left kidney with large central necrosis in low signal on T1 and high signal on T2. It involved the tail of the pancreas without adenopathy or vascular extension. The diagnosis of bilateral renal cancer associated with polycystic kidney disease was considered. A bilateral nephrectomy was decided.

The first surgical exploration revealed locally advanced tumor with invasion of transverse mesocolon and pancreas tail, with ascites. A radical left nephrectomy was performed (Figure 4).

At histopathologic examination, the left kidney was 1 Kg 500 in weight and 20 cm in length. The renal parenchyma was multicystic with a tumor of 8 cm containing hemorrhagic and necrosis components. Histologic examination showed a fusiform cells proliferation with cytonuclear atypies and elevated mitotic index infiltrating the perirenal fat tissue, renal capsule, pancreas and left mesocolon (Figure 5).

Immunohistochemical examination showed an intense and positive staining with vimentine (Figure 6). The staining with actine, desmine, cytokeratin and myogenine was negative. The diagnosis of high-grade pleomorphic sarcoma was confirmed. Right nephrectomy could not be performed.

The association between adult polycystic kidney disease and renal cell carcinoma has been reported in about thirteen cases [3-5], whereas the association with sarcoma is a very uncommon situation. To our knowledge, it has been reported in only three cases [1,6,7].

Due to increased survival of patients with APKD undergoing dialysis and renal transplantation, coexisting malignant tumor should be considered when complex cysts are discovered within the kidney on imaging performed for various symptoms or for screening [1,4,5].

Any asymmetry in size and shape of the kidneys, a definite palpable mass, hematuria and unexplained fever or weight loss, all indicate the need for a careful further investigation in patients with polycystic disease [5].

Imaging of these patients is further made complex by the marked distortion of the renal architecture due to the underlying polycystic disease. A combination of various imaging modalities is necessary to make a definite preoperative diagnosis [5].

A complex cyst on ultrasound examination, any solid mass on CT and/or MR should be investigated by fine needle aspiration cytology or biopsy [5].

Sarcomas of the kidney are uncommon; they represent 1% to 3% of all malignant renal tumors. Macroscopically, the tumors are voluminous [mean size = 19.5 cm]. Like other genitourinary sarcomas, most of these lesions are histologically high-grade (86%) and are greater than 5 cm in size at diagnosis (56%) [1,8].

Primary renal sarcomas have imaging features of malignant tumor without histological specificity. They cannot be differentiated from other renal cancers or retroperitoneal sarcoma [9].

Ultrasonography shows an echoic solid mass involving the renal parenchyma.

On enhanced CT series, the tumor is often voluminous without capsule and is heterogeneous with central necrosis. After contrast injection, the enhancement is variable [9].

CT scan is also useful in evaluating loco-regional extension, venous invasion and permits to diagnose thoracic or hepatic secondary localizations [9].

There is no specific signal for this tumor in MRI but it permits to detect local extension and venous invasion like in other malignant tumor of kidney.

The primary treatment for renal sarcoma is complete resection with histologically negative margins [1].

Complete tumor resection is possible only in 72% of patients with renal sarcomas and 86.6% of them die within 23 months after surgery [1].

Sarcoma associated with APKD is very rare and have similar radiological features as primary renal sarcoma or carcinoma which require histological evaluation for definitive diagnosis.