CYSTIC TUMORS OF THE KIDNEY BOSNIAK III: CORRELATION HISTOPATHOLOGICAL-RADIOLOGICAL-SURGICAL: ABOUT 12 CASES Y.BEN CHEIKH, N.MAMA, F. MALLAT, F.BOUZEYAN, F. EL OUNI, N. ARIFA, H.JEMNI, K.TLILI. Department of Medical Imaging, Sahloul Hospital, 4000 Sousse, Tunisia URINARY : UR 17

Introduction Complex indeterminate renal cystic masses (Bosniak type III) can have benign and malignant causes and have been traditionally considered as surgical lesions. Their surgical exploration is discussed: it is difficult to affirm or reverse the malignant tumors of Class III. Criteria for radiological diagnosis of cystic tumors Bosniak III imaging (ultrasound but especially CT and MRI) are established. The objective of this work is to correlate imaging abnormalities with operative and histopathological findings.

Materials and methods  We reviewed the clinical, radiological, operative and anapathological data of 12 patients operated at the Urology department in Sahloul hospital, between 2002 and 2010 for Bosniak III cystic tumors. All patients underwent sonography, 10 of them had an enhanced-contrast CT 2 had an MRI given the kidney failure.

Results The average age : 51 years sex ratio: 8H/4F  The most common reasons for consultation were low back pain with hematuria

Results All patients were operated for a Bosniak III cystic lesion. Intraoperative, highly suspicious lesions were found in 5 cases which led to nephrectomy.

A C D 60-year-old men with cystic renal cell carcinoma. A - Ultrasound of multilocular cyst  B - Axial unenhanced CT image shows hypodense lesion with faint septa. C and D, Axial contrast-enhanced CT images show thick enhanced septa B

55-year-old woman with cystic nephroma Axial contrast-enhanced CT images show multilocular cyst with thick enhancing septa

A B 56-year-old men with tubulo papillary carcinoma A - Axial unenhanced CT image shows multilocular lesion spontaneously hyperdense and heterogeneous. B - Axial contrast-enhanced CT image don’t shows any enhancement of the septa

B C 75-year-old men with splenic and renal cavernous hemangioma. A - Axial contrast-enhanced CT image show a multilocular splenic lesion B - Axial unenhanced CT image show lesion spontaneously heterogeneous with hyperdense foci. C - Axial contrast-enhanced CT images show a mild enhancement A

Discussion Renal cysts are a common finding on routine radiological studies. As such, patients are often referred to urologists for their opinion regarding potential intervention and follow-up. In 1986, Bosniak classified renal cysts in four categories on the basis of imaging appearances in an attempt to predict the risk of malignancy. Subsequent studies have shown that the Bosniak system is helpful in assessing the risk of malignancy in cystic renal lesions . The Bosniak system classifies not only lesions into categories on the basis of CT imaging appearances but also advocates treatment for each category.

Category I cysts have no malignant potential and, as such, no follow-up is required. However, there is a large difference in potential malignant risk, between category II and category III. These are 0% to 5% and about 50%, respectively. To clarify this further, a subcategory of II was developed, IIF (for “follow-up”). Category IIF identifies the category II cyst which was slightly more complicated, but not necessarily suspicious enough to warrant surgical exploration.

The recommended treatment for Bosniak category III lesions is surgical resection. The disadvantage of this approach is that up to 40–60% of patients with Bosniak category III lesions undergo surgery for benign lesions. If a large number of category II or IIF cysts are placed in category III, a higher percentage of category III lesions will turn out to be benign. Therefore, we can expect a wide variation in the relative number of benign and malignant category III cases in the various series reported in the literature. In our serie, 7 of 12 cystic masses were malignant. The second lecture of their exams found 4 Bosniak IV lesions that have been described initially as Bosniak III. Surgery in these patients ranges from exploration and biopsy to enucleation, partial nephrectomy, and nephrectomy . In general, these lesions occur in patients over 50 years-old, and surgery in this patient population can result in significant morbidity.

Etiology of BOSNIAK category III lesions

Cystic Clear Cell Carcinoma Macroscopically, clear cell Renal carcinoma presents as a solid or a cystic pattern. The cystic pattern accounting for 4–15% of all RCCs. Four mechanisms by which RCC can appear cystic at imaging have been described: intrinsic unilocular cystic growth, intrinsic multilocular cystic growth, cystic necrosis (pseudocyst), origin in the epithelium of a simple cyst Cystic RCC is seen on MRI and CT as a water-attenuation mass with an enhancing thick wall or septa , sometimes with associated soft-tissue nodules. Nodular and septal enhancement is the most sensitive finding to discriminate cystic RCC from complex benign lesions

Multilocular Cystic Renal Cell Carcinoma Rare entity Incidence of 1–4% of all RCCs. Adults between 20 and 76 years old . Usually, it is asymptomatic, and it is incidentally discovered. It has an excellent prognosis compared with conventional RCC. Whatever the size, multilocular cystic RCC may be regarded as a definitively low-grade tumor when strict defining criteria are applied.

Multilocular Cystic Renal Cell Carcinoma (2) Characterized by septate variably sized cysts separated from the kidney by a fibrous capsule. The cyst fluid may be serous or hemorrhagic and thus can be of water attenuation or higher. Imaging : Multilocular cystic tumor with wall and septal contrast enhancement without any expansile tumor nodule. Asymmetric septal thickening may be seen. Twenty percent of tumors show septal or wall calcification. 63-year-old man with multilocular cystic renal cell carcinoma. A- Axial unenhanced CT image shows lesion (arrow) isodense to renal parenchyma extending into renal sinus. B- Axial contrast-enhanced CT image shows mural thinning and perceptible septal enhancement (arrowhead). AJR:192, May 2009

Cystic Nephroma The cystic components of cystic nephroma are of variable size and are lined with flat low cuboidal or hobnail epithelial cells, and septa are thin with variable cellularity. Many pathologists believe that cystic nephroma is a benign neoplasm that lies at the benign end of a continuum that includes the cystic, partially differentiated nephroblastoma variant of Wilms’ tumor. The cystic nephroma has a bimodal age distribution : Under the age of 5 years, cystic nephroma occurs most frequently in males The adult group has a female predominance, occurring most commonly between the ages of 40 and 60 years.

Cystic Nephroma (2) The most common presenting symptoms are a painless abdominal mass, abdominal or flank pain, and occasionally hematuria. Imaging : Septate cystic mass with multiple loculations Hairlike septa Peripheral and curvilinear calcifications, Irregular borders Minimal contrast enhancement. Extension into the central sinus and into the renal pelvis can also be found.

Mixed Epithelial and Stromal Tumor Benign renal neoplasm Characterized by a biphasic proliferation of epithelium and stroma and, morphologically, by admixed solid and cystic regions that have variable cellularity and growth patterns . The tumor nearly always occurs in women, especially in perimenopausal usually presenting with flank pain and hematuria or diagnosed incidentally during investigations for other problems . Imaging : Lesion with septa, curvilinear calcifications, and a delayed enhancing solid component Areas of decreased signal on T2-weighted MR images, reflecting a fibrotic component, can also be found.

Complex Benign Cystic Renal Lesions Simple renal cysts are commonly observed in normal kidneys They are benign asymptomatic lesions that do not require treatment. Cysts may manifest complex features as a result of hemorrhage, infection, or inflammation

conclusion Bosniak category III lesions do not mean malignancy. These lesions should not need surgical exploration initially as these lesions can be stratified into malignant and benign groups at imaging-guided biopsy, thus preventing unnecessary surgery in up to 40% of patients.