Extrarenal Wilms" tumor is extremely rare. Approximately 54 cases have been reported in the world literature through 1993. Only eight extrarenal Wilms" tumors were enrolled in the National Wilms" Tumor Study (NWTS) between 1980 and 1986. These cases constituted a fraction of 1% of all Wilms" tumors reported to the N.W.T.S during this period. The authors report a case of retroperitoneal Wilms" tumor (Stage III) presenting as a lower abdominal mass in a previously healthy 6-year-old girl who was operated and staged according to the current N.W.T.S III criteria.

Hydatid disease is one of the oldest diseases known to humankind. In 85-95% of the cases, the liver and/or the lungs are involved and only 5-15% of other organs. The case presented here is a 38-year-old man with hydatid disease of lower lumbar vertebrae, sacrum, lumbosacral spinal canal, and left iliac bone; with extension to RETROPERITONEUM and piriformis, sacrospi-nalis, iliacus, iliopsoas, and quadratus lumbarum muscles; without involvement of liver or lung, as diagnosed by MRI and CT scan and confirmed by surgery.

Introduction: Posterior mediastinal cysts are rare and constitute a small but important diagnostic group of mediastinal masses. The aim of presenting this case is to highlight rarity and unusual presentation.Case Report: A case of mesenchymal cyst located on the posterior mediastinum extending into the RETROPERITONEUM in a 45-year-old man who was presented with sciatic pain in his left lower extremity was referred to our clinic. Preoperative MRI study revealed evidence of a left L5-S1 disc herniation and a 10 cm aortic aneurism anterior to the spinal column (T10-L1). Radiologic studies showed a large homogeneous unilocular cystic mass in the mediastinum (between the aorta and vena cava) extending into the retroperitoneal space across the diaphragm. Diagnosis was confirmed with histopathologic examinations.Conclusion: Surgical resection is the treatment of choice for most cysts occur in the mediastinum but some authors do not recommend surgical removal as primary treatment for small and asymptomatic simple mediastinal cysts. Excision of simple mediastinal cysts is indicated for diagnostic purposes only.

Introduction: Extrarenal angiomyolipoma is an uncommon disease entity and is rare in the RETROPERITONEUM. This lesion shows three benign components, including mature adipose tissue, thick-walled blood vessels, and smooth muscles. Case Report: This report describes a 37-year-old woman who presented with incidental right retroperitoneal mass in prenatal checkup. The patient underwent excisional surgery. Histological examinations and the immunohistochemical study revealed angiomyolipoma. Based on the diagnosis, the patient received no more treatment. After 3 years of close followup examinations, no recurrence was observed. Conclusion: This diagnosis is often confused with many other entities in RETROPERITONEUM. Thus, imaging and histologic correlation are required. Proper diagnosis is essential for further patient management and avoids unnecessary treatment.

Objective: The presence of air within the mediastinal compartment and retro-peritoneal compartment, in the setting of trauma, can be because of visceral and skeletal injuries. However, in absence of a local site injury, an approach based on anatomical communication between various body compartments should be utilized and all potential sites of injuries must be reviewed. Case Presentation: We present a case of a 40-year-old male patient with a history of trauma (fall from height), presenting to the emergency department with loss of consciousness and ear bleed. Chest radiographs showed pneumomediastinum. On cross-sectional imaging, pneumomediastinum and pneumoRETROPERITONEUM were seen, however no esophageal, tracheal and skeletal injuries could be identified. On careful evaluation, fractures involving the base of skull were identified as a source of ectopic air. Conclusion: This case represents a situation where the fascial connections between various compartments of the body were utilized to find the site of injury and hence the source of ectopic air. Base of skull fractures are important to be identified since these require surgical attention at an early stage.

A case of abdominal mass was studied by dynamic computed tomography (CT), magnetic resonance imaging (MRI) and hepatic angiography. The results of radiological examinations made the diagnosis even more confusing. The patient underwent laparotomy under a preoperative diagnosis of hepatic tumor. The tumor was finally diagnosed as a benign retroperitoneal neurilemmoma by histological examination. This case indicated that careful examination is necessary to determine whether it arises from the liver itself or from neighboring tissues. Radiological examinations are not reliable sometimes.

Herein, we report on a well-characterized benign metastasizing leiomyoma, presented in an unusual site. Up to the knowledge of authors, so far, only 76 cases of benign metastasizing leiomyoma have been reported. The tumor presented as a retroperitoneal mass three years after a hysterectomy Performed for leiomyomatosis of the uterus with extensive areas of hyalinization. Histopathologic and immunohistochemical studies of the resected mass were similar to the uterine leiomyoma, showing moderate cellularity of bland looking smooth muscle cells with minimal atypia, inconspicuous mitosis, and no necrosis in a hyalinized background.

Background: Retroperitoneal schwannoma is a rare tumor rising from Schwann cells in peripheral nerve sheaths. Retroperitoneal schwannoma is really infrequent and has nonspecific symptoms and imperfect radiologic features, and is often identified histologically after surgery. Case Report: We report the case of a 73-year-old man presented with flank mass. Imaging shows a hypoechoic macro lobulated solid cystic mass in RETROPERITONEUM. Intraoperatively, after complete resection of retroperitoneal mass, a suspected lesion in upper pole of right kidney was observed. Histopathology evaluation after surgery shows coexistence of a large retroperitoneal schwannoma and papillary renal cell carcinoma, type 1. Conclusion: Schwannoma should be considered in the differential diagnosis of retroperitoneal spindle cell tumor. Schwannoma coexisted with renal cell carcinoma in a patient is an unusual event. Thus, it can show the importance of appropriate evaluation before any surgery.