Retroperitoneal sarcoma: a 10-year follow-up analysis using hospital-based cancer registry data in Japan.

OBJECTIVES: We sought clinical characteristics, survival outcomes, and prognostic factors for overall survival of retroperitoneal sarcoma in Japan. METHODS: A Japanese hospital-based cancer registry database with a pivotal 10-year follow-up was used to identify and enroll patients, registered from 106 institutions, diagnosed with retroperitoneal sarcoma in 2008-2009. Treating hospitals were divided by hospital care volume; high-volume hospitals and low-volume hospitals were defined as ≥ 4 and < 4 cases/year, respectively. RESULTS: A total of 91 men and 97 women were included, with a median age of 64 years. The most common histological type was liposarcoma in 101 patients, followed by leiomyosarcoma in 38 patients. The 5-year and 10-year overall survival rates were 44.1 and 28.3%. The majority of patients (n = 152, 80.9%) were treated at low-volume hospitals. High-volume hospital patients had higher 10-year overall survival rates than low-volume hospital patients (51.2% vs 23.2%, P = 0.026). Multivariate analysis revealed age over 60 years, treatment in low-volume hospitals and chemotherapy were independent predictors of unfavorable survival while treatment with surgery was an independent predictor of favorable survival. CONCLUSIONS: The possibility of surgical removal was suggested to be the most important prognostic factor for retroperitoneal sarcoma. Better survival was shown in patients treated at high-volume hospitals in our series.

Incidence, Treatment and Outcome of Patients with Retroperitoneal Soft-Tissue Sarcoma in Switzerland 2005-2015: A Population-Based Analysis.

BACKGROUND: Reports on the epidemiology and mortality of retroperitoneal soft tissue sarcoma (RSTS) in Switzerland are scarce. This study investigates the incidence and outcomes of surgically treated RSTS inpatients in Switzerland depending on the hospital type and size. METHODS: Data from the Swiss Federal Statistical Office were used to conduct a retrospective analysis of all RSTS inpatients and hospitalizations in Switzerland between 2005 and 2015. RSTS was identified by the code C48.x of the International Classification of Diseases (ICD-10). Sarcoma centers were identified by the annual total number of sarcoma patients (> 50 patients/year). The analysis of yearly incidence, age distribution as well as in-hospital complication and mortality was performed for non- and surgical-treated patients. A centralization of treating sarcoma patients was analyzed by the trend of hospitalizations in sarcoma centers and high-volume hospitals. RESULTS: During 2005-2015, 2.801 hospitalizations (1651 patients) were admitted to Swiss hospitals with the primary diagnosis of a RSTS. The yearly number of RSTS patients and the incidence (1.91/100.000) stayed constant within these 11 years. There were five sarcoma centers. We saw a clear trend of RSTS patients being treated (especially surgically) in centers over the 11 years. The complication rate of surgical-treated patients was higher in sarcoma centers (55% vs. 40%), though the overall mortality rate was lower (3.2% vs. 9.1%). CONCLUSION: Centralization of RSTS treatment to certified sarcoma centers leads to a lower overall mortality rate and thus is highly recommended.

Percentage of Teratoma in Orchiectomy and Risk of Retroperitoneal Teratoma at the Time of Postchemotherapy Retroperitoneal Lymph Node Dissection in Germ Cell Tumors.

PURPOSE: Presence of teratoma in the orchiectomy and residual retroperitoneal mass size are known predictors of finding teratoma during postchemotherapy retroperitoneal lymph node dissection (PC-RPLND). We sought to determine if the percentage of teratoma in the orchiectomy specimen could better stratify the risk of teratoma in the retroperitoneum. MATERIALS AND METHODS: The Indiana University Testis Cancer Database was reviewed to identify patients who underwent PC-RPLND for nonseminomatous germ cell tumors from 2010 to 2018. A logistic regression model was fit to predict the presence of retroperitoneal teratoma using teratoma and yolk sac tumor in the orchiectomy, residual mass size and log transformed values of prechemotherapy alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin. The study cohort was split into 60% training and 40% validation sets using 200 bootstraps. A predictive nomogram was developed for predicting teratoma in the retroperitoneum. RESULTS: A total of 422 men were included. Presence of teratoma in the orchiectomy (OR 1.02, p <0.001), residual mass size (OR 1.16, p <0.001) and log transformed prechemotherapy AFP (OR 1.12, p=0.002) were predictive factors for having teratoma in the retroperitoneum. The C-statistic using this model demonstrated a predictive ability of 0.77. Training set C-statistic was 0.78 compared to 0.75 for the validation set. A nomogram was developed to aid in clinical utility. CONCLUSIONS: The model better predicts patients at higher risk for teratoma in the retroperitoneum following chemotherapy, which can aid in a more informed referral for surgical resection.

Risk Assessment of Visceral Sarcomas: A Comparative Study of 2698 Cases from the SEER Database.

Soft tissue sarcomas arising in visceral organs are rare and lack validated tumor-staging protocols. Clinicopathologic features and clinical outcomes of 2698 visceral sarcomas identified in the Surveillance, Epidemiology, and End Results Program (SEER) database were compared with sarcomas arising in the extremities/trunk (n = 10,237) or retroperitoneum (n = 1067) using standard statistical techniques. Important prognostic criteria for visceral sarcomas, as in other anatomic sites, included tumor size, histologic grade, and presence of metastatic disease. After adjustment for pertinent confounding factors, visceral sarcomas showed cancer-specific survival rates similar to those arising in the retroperitoneum but had worse outcomes than sarcomas in the extremities/trunk. Therefore, the prognostic performance of two different staging algorithms for retroperitoneal sarcomas was evaluated for their use in staging sarcomas of visceral organs. The current AJCC 8th edition and the recently derived Vanderbilt system for staging retroperitoneal sarcoma both showed adequate discrimination, as assessed by multiple clinical concordance indices, and no evidence of miscalibration. Therefore, the authors concluded that previously validated staging systems for retroperitoneal sarcomas based on conventional prognostic factors (histologic grade, tumor size, and presence of metastatic disease) are applicable to visceral sarcomas and should be incorporated into the next edition of the AJCC Cancer Staging Manual.

Prognostic factors of metastatic myxoid liposarcoma.

BACKGROUND: Myxoid liposarcoma (MLS) has the tendency to metastasize extrapulmonary. Although prognostic factors at the initial diagnosis of MLS have been reported, those at diagnosis of metastasis remain unclear. The purpose of this study was to investigate the prognostic factors for disease-specific survival at the initial diagnosis of metastasis. METHODS: This retrospective observational study was conducted at three cancer centers and two university hospitals in Japan. Of 274 MLS patients pathologically diagnosed between 2001 and 2015, 48 metastatic patients were examined. RESULTS: Lung metastases were detected in nine patients (18.8%) and extrapulmonary metastases in 45 (93.8%). Interval from primary diagnosis to the first metastasis was significantly shorter in patients with lung metastases than without (p = 0.007). Median disease-specific survival after diagnosis of metastases was 52.5 months in all patients. In multivariable analysis, liver metastasis (hazard ratio (HR), 2.71 [95% confidence interval (CI), 1.00-7.09]) and no evidence of disease (NED) achieved by radical treatment (resection with or without radiation therapy, or radiation therapy ≥60 Gy) or semi-radical (radiation therapy ≥40 Gy) treatment were significantly related to survival (HR, 0.36; 95%CI [0.13-0.95]). The number of metastases (odds ratio (OR), 0.44; 95%CI [0.25-0.78]) and abdominal/retroperitoneal metastases (OR, 0.09; 95%CI [0.008-0.95]) were the significant inhibitory factors of achieving NED. CONCLUSIONS: This is the first study to statistically demonstrate the importance of achieving NED with surgical resection or radiation therapy for longer survival in metastatic MLS patients. As number of metastases was a significant factor for achieving NED, early detection of metastases might be important.

Primary localized retroperitoneal sarcomas: report from Slovenian sarcoma referral center.

BACKGROUND: Sarcoma patients should be treated in high volume referral sarcoma centers. Compartmental resection is proposed as the best treatment option in retroperitoneal sarcoma patients. METHODS: Institute of Oncology Ljubljana is the only referral sarcoma center in Slovenia. Having a population of 2.1 million poses a unique situation. We manage all sarcoma patients in the country and operate on patients with soft tissue tumors of extremities, trunk, and abdomen. Data for all consecutive patients surgically treated from January 1999 to December 2018 for primary localized retroperitoneal sarcoma was extracted from a prospective surgical database. Data about the incidence of sarcoma patients in Slovenia was extracted from the Cancer Registry of Republic of Slovenia. Clinicopathologic variables and the outcome were analyzed. RESULTS: In total, 89 patients were included in the study. Median age was 62 years. Dedifferentiated liposarcoma was the most common histology (38.2%). Median tumor size was 21 cm. Compartmental resection was performed in 47.2% (42/89). Postoperative complication grade 3a or higher according to Clavien-Dindo classification had 30.3% (27/89) of patients. The 30-day and 90-day mortality rate was 2.2% and 5.6%. Median follow-up was 62.1 months. Corresponding 5-year overall survival was 67.2%, 5-year disease-specific survival was 72.6%, and 5-year local recurrence-free survival was 81.5%, respectively. CONCLUSION: Results from our institution show that referral sarcoma centers may achieve very good results in management of retroperitoneal sarcoma patients, despite not meeting the criteria for high volume hospitals, as long as they have multidisciplinary team, appropriate facilities, and expertise.

Recurrence patterns after resection of retroperitoneal sarcomas: An eight-institution study from the US Sarcoma Collaborative.

BACKGROUND AND OBJECTIVES: Resection of primary retroperitoneal sarcomas (RPS) has a high incidence of recurrence. This study aims to identify patterns of recurrence and its impact on overall survival. METHODS: Adult patients with primary retroperitoneal soft tissue sarcomas who underwent resection in 2000-2016 at eight institutions of the US Sarcoma Collaborative were evaluated. RESULTS: Four hundred and ninety-eight patients were analyzed, with 56.2% (280 of 498) having recurrences. There were 433 recurrences (1-8) in 280 patients with 126 (25.3%) being locoregional, 82 (16.5%) distant, and 72 (14.5%) both locoregional and distant. Multivariate analyses revealed the following: Patient age P = .0002), tumor grade (P = .02), local recurrence (P = .0003) and distant recurrence (P < .0001) were predictors of disease-specific survival. The 1-, 3-, and 5-year survival rate for patients who recurred vs not was 89.6% (standard error [SE] 1.9) vs 93.5% (1.8), 66.0% (3.2) vs 88.4% (2.6), and 51.8% (3.6) vs 83.9% (3.3), respectively, P < .0001. Median survival was 5.3 years for the recurrence vs 11.3+ years for the no recurrence group (P < .0001). Median survival from the time of recurrence was 2.5 years. CONCLUSIONS: Recurrence after resection of RPS occurs in more than half of patients independently of resection status or perioperative chemotherapy and is equally distributed between locoregional and distant sites. Recurrence is primarily related to tumor biology and is associated with a significant decrease in overall survival.

Postoperative Morbidity After Radical Resection of Primary Retroperitoneal Sarcoma: A Report From the Transatlantic RPS Working Group.

OBJECTIVE: To investigate the safety of radical resection for retroperitoneal sarcoma (RPS). BACKGROUND: The surgical management of RPS frequently involves complex multivisceral resection. Improved oncologic outcomes have been demonstrated with this approach compared to marginal excision, but the safety of radical resection has not been shown in a large study population. METHODS: The Transatlantic Retroperitoneal Sarcoma Working Group (TARPSWG) is an international collaborative of sarcoma centers. A combined experience of 1007 consecutive resections for primary RPS from January 2002 to December 2011 was studied retrospectively with respect to adverse events. A weighted organ score was devised to account for differences in surgical complexity. Univariate and multivariate logistic regression analyses were performed to investigate associations between adverse events and number and patterns of organs resected. Associations between adverse events and overall survival, local recurrence, and distant metastases were investigated. RESULTS: Severe postoperative adverse events (Clavien-Dindo ≥3) occurred in 165 patients (16.4%) and 18 patients (1.8%) died within 30 days. Significant predictors of severe adverse events were age (P = 0.003), transfusion requirements (P < 0.001), and resected organ score (P = 0.042). Resections involving pancreaticoduodenectomy, major vascular resection, and splenectomy/pancreatectomy were found to entail higher operative risk (odds ratio >1.5). There was no impact of postoperative adverse events on overall survival, local recurrence, or distant metastases. CONCLUSIONS: A radical surgical approach to RPS is safe when carried out at a specialist sarcoma center. High-risk resections should be carefully considered on an individual basis and weighed against anticipated disease biology. There appears to be no association between surgical morbidity and long-term oncologic outcomes.

Surgical morbidity in retroperitoneal sarcoma resection.

Resection of retroperitoneal sarcoma (RPS) typically involves multivisceral resection. The morbidity of RPS resection has decreased over time despite widespread adoption of radical resection. Certain patterns of resection are associated with higher complication rates and elderly patients are at increased risk of morbidity. Administration of preoperative radiotherapy does not increase morbidity, but intraoperative and brachytherapy techniques are associated with heightened toxicities. Long-term functional outcomes and quality of life scores after RPS resection are acceptable.

Anterior Approach to En Bloc Resection in Left-Sided Retroperitoneal Sarcoma with Adjacent Organ Involvement: A Study of 25 Patients in a Single Center.

BACKGROUND There is no standard surgical approach for the management of retroperitoneal sarcoma. The aim of this clinical study was to describe the experience of an anterior approach to en bloc resection in left-sided retroperitoneal sarcoma with adjacent organ involvement. MATERIAL AND METHODS This retrospective clinical study included 25 patients who were diagnosed with left-sided retroperitoneal sarcoma and underwent tumor resection at a single center between May 2012 and July 2017. All patients had tumors that were adjacent to the left colon, pancreas, left kidney, left adrenal gland, and psoas major; some of the tumors were adjacent to the diaphragm, stomach, and small intestine. An anterior approach was used to remove the left-sided retroperitoneal tumor with the adhesive organs en bloc, an approach that is described in detail. The value of this surgical approach was evaluated based on the histopathological findings, postoperative complications, and patient follow-up. RESULTS The median number of resected organs, in addition to the retroperitoneal tumor, was 8 (range, 6-10). Complete macroscopic tumor resection was achieved in 23 cases (92%). Twenty-four patients (96%) had tumor infiltration of at least one organ or the surrounding fat. Three patients (12%) experienced Grade III and IV postoperative morbidities. The one-year disease-free survival rate was 91.3% among patients with macroscopically complete resections. The one-year overall survival rate was 83.2%. CONCLUSIONS In selected patients, left-sided retroperitoneal sarcoma associated with local organ involvement can be surgically managed using an anterior approach with en bloc resection of adjacent organs.

Demographics, management and treatment outcomes of benign and malignant retroperitoneal tumors in Japan.

OBJECTIVES: To show the demographics, type of treatment and clinical outcomes of patients with retroperitoneal tumors in Japan. METHODS: We carried out a retrospective analysis of patients with retroperitoneal tumors treated between 2000 and 2012 at 12 university hospitals in Japan. Histology was re-evaluated using the 2013 World Health Organization classification. RESULTS: A total of 167 patients were included in the analysis. The number of diagnosed patients increased over the 12-year study period. Liposarcoma and schwannoma were the most common histological types among intermediate/malignant and benign tumors, respectively. The intermediate/malignant tumors were larger and were more frequently found in older people. Surgical resection was the primary treatment for 151 patients. The median survival duration for patients with malignant tumors was 91 months, and was significantly shorter than that for patients with benign and intermediate tumors (P < 0.01). R2 resection was associated with significantly shorter survival than R0/R1 resection for malignant tumors (P < 0.01), but not for intermediate. Grossly complete resection of the recurrent tumors improved survival. CONCLUSION: The number of patients diagnosed with retroperitoneal tumors increased over time. R2 resection of primary tumors was found to be associated with poor prognosis in malignant tumors, but not in intermediate tumors. Complete surgical resection of recurrent tumors was associated with a better oncological outcome.

Primary Retroperitoneal Cystoadenocarcinoma: A Systematic Review.

BACKGROUND/AIMS: The aim of this study was to perform a systematic review on primary retroperitoneal cystoadenocarcinoma (PRC), which is an extremely rare disease. METHODS: According to PRISMA guidelines, all the literature about PRC from 1977 to 2015 was reviewed. Thirty articles were selected; characteristics of the patients were collected and described; time to recurrence and overall survival (OS) were investigated when available. RESULTS: Thirty seven patients were included of whom 33 were females; the median age at presentation was 43. PRC was more common in postmenopausal women. Surgery was the standard therapy; the role of chemotherapy and/or radiotherapy was uncertain. Thirty percent of the patients relapsed after 58 months from the surgery; the rupture of the cyst occurred in 13% of the cases and it was associated with poor prognosis as well as premenopausal status. At 125 months from the diagnosis, 72% of the patients were alive and the median OS was not reached. CONCLUSIONS: The present systematic review about PRC is the first performed until the date of drafting this paper. We described some clinical features of PRC and their possible prognostic value. No conclusive data can be presented due to the small population analyzed and to publication bias.

Value of surgical resection in children with high-risk neuroblastoma.

BACKGROUND: The value of gross total resection (GTR) for children with high-risk neuroblastoma (NB) is controversial. We hypothesized that patients undergoing GTR would demonstrate improved overall survival (OS) compared those having 90% resection compared to <90% resection (P = 0.008). Multivariable Cox models confirmed these findings with improved survival in children undergoing >90% vs. <90% resection but no difference in GTR vs. 90% resection is associated with improved OS compared to less than 90% resection.

Increased incidence of retroperitoneal teratomas and decreased incidence of sacrococcygeal teratomas in infants with Down syndrome.

Individuals with Down syndrome (DS) have a unique profile of neoplasms, with a higher incidence of leukemias and a lower incidence of solid tumors than seen in the general population. We recently encountered two cases of infants with DS with retroperitoneal teratoma. After reviewing the literature on teratomas in DS, we found that the incidence of retroperitoneal teratomas was higher and the incidence of sacrococcygeal teratomas was lower in infants with DS than in the general population.

Sclerosing variant of well-differentiated liposarcoma: relative prevalence and spectrum of CT and MRI features.

OBJECTIVE: The purpose of this study was to determine the relative prevalence of the sclerosing variant of well-differentiated liposarcoma at one institution and to elucidate the CT and MRI characteristics of this subtype of well-differentiated liposarcoma. MATERIALS AND METHODS: A retrospective computerized search was conducted to calculate the relative prevalence of the sclerosing variant of well-differentiated liposarcoma among all well-differentiated liposarcoma subtypes at one institution. The MRI and CT features of a total of 19 cases of pathologically proven sclerosing variant of well-differentiated liposarcoma were evaluated (seven identified from the study institution database and 12 cases contributed by other institutions). RESULTS: The cases of a total of 36 patients with well-differentiated liposarcoma were identified in the pathology database; six (17%) cases had evidence of dedifferentiation. Seven (19%) cases of sclerosing variant of well-differentiated liposarcoma were identified. Of these, three (43%) had evidence of dedifferentiation. On images, the sclerosing variant of well-differentiated liposarcoma typically presented as a large (average, 16.6 cm) well-circumscribed heterogeneous mass most commonly situated in the retroperitoneum (58%). Sixteen of the 19 tumors evaluated (84%) had predominantly well-circumscribed margins. Tumor composition ranged from predominantly fatty to entirely devoid of macroscopic fat; only three (16%) were composed of more than 75% fat. Variable amounts of nonlipomatous elements were identified in all cases. Enhancement of these elements was evident at CT or MRI in all 14 cases in which enhancement could be reliably assessed. CONCLUSION: The sclerosing variant of well-differentiated liposarcoma should be included in the differential diagnosis of any well-circumscribed lipomatous mass containing variable amounts of nonlipomatous elements, particularly when located in the retroperitoneum. Unlike other subtypes of well-differentiated liposarcoma, the sclerosing variant is less likely to be composed predominantly of fat and may be associated with an increased propensity for dedifferentiation.

Reducing morbidity of pelvic and retroperitoneal lymphadenectomy.

Lymphadenectomy is utilized in both pelvic and retroperitoneal oncological surgery as a means to eradicate locoregional disease, improve staging accuracy and guide adjuvant therapy. However, pelvic and retroperitoneal lymphadenectomy have the potential for morbidity including lymphatic injury, vascular injury, thromboembolic events and neurologic injury. Across the spectrum of urologic malignancies, the evidence supporting both the necessity and the extent of lymphadenectomy varies considerably. Awareness of the potential for injury and ways to avoid and manage the most common complications is necessary to decrease the morbidity associated with these procedures.

Pediatric retroperitoneal non-organ-originated malignancies: An analysis based on SEER database.

Retroperitoneal non-organ-originated malignancies are rare pediatric tumors with challenging diagnosis and treatment. The present study aimed to analyze the clinicopathological characteristics, treatment, and prognosis of retroperitoneal non-organ-originated malignancies. In the study, we included the pathological diagnosis of pediatric retroperitoneal non-organ-originated malignant tumors between 2000 to 2019 through the updated Surveillance, Epidemiology, and End Results database. We use the Kaplan-Meier survival curve to calculate the overall survival (OS) and cancer-specific survival (CSS). The risk of all-cause death and disease-specific death were analyzed using Cox proportional hazard regression model and Fine-and-Grey competitive hazard model, respectively. In the study, a total of 443 pediatric retroperitoneal non-organ-originated malignancies were included. Of them, only 22.3% of patients had no metastatic disease, 42.9% had distant metastasis and 34.8% had locally advanced diseases. The primary pathological tumor was neuroblastoma followed by germ cell tumor. The overall 10-year OS and CSS were 70.7% and 73.1%, respectively, and the 10-year OS and CSS of metastatic diseases were 54.4% and 56.6%, respectively. Older children, worse tumor stage at diagnosis, incomplete resection, and prolonged time from diagnosis to treatment were significantly associated with worse survival outcomes. Radiotherapy and chemotherapy did not significantly improve the prognosis of patients without complete tumor resection. The study indicated that most pediatric retroperitoneal non-organ-originated malignancies diagnosed with metastatic diseases have plagued treatment. Radiotherapy and chemotherapy are the main treatment methods for children unable to undergo complete surgical treatment. However, these treatments do not reach the same therapeutic effect as complete tumor resection after early diagnosis. Hence, early diagnosis and surgery for complete tumor resection are of utmost importance.

Abdominal soft tissue sarcoma: a multicenter retrospective study.

BACKGROUND: Soft tissue sarcomas (STS) are rare mesenchymal neoplasms with a variety of histological subtypes. However, in Japan, data on the clinical characteristics and prognostic profiles of these tumors are lacking. The purpose of the present study was to clarify the clinical features and outcomes of Japanese patients with retroperitoneal and abdominal STS. METHODS: We reviewed and analyzed retrospectively the data for 82 patients who underwent surgery for retroperitoneal and abdominal STS at Osaka University and affiliated hospitals from 2000 to 2007. The factors analyzed included patient demographics and clinical features. RESULTS: The histological subtypes included leiomyosarcoma in 32 patients (39.0%), liposarcoma in 30 (36.6%), malignant fibrous histiocytoma in 10 (12.2%), and other miscellaneous subtypes in 10 (12.2%). The overall survivals were 92, 69, and 62%, respectively, at 1, 3, and 5 years after primary surgery. The overall survival of patients with low-grade sarcoma was significantly better than that of patients with high-grade sarcoma. Complete resection was done in 63 patients (77%) and their recurrence-free survivals were 73, 34, and 23%, respectively, at 1, 3, and 5 years after the surgery. Subgroup analysis of differences between leiomyosarcoma and liposarcoma revealed that liposarcomas were mainly located in the retroperitoneum and leiomyosarcomas were located equally in the retroperitoneum and abdominal cavity. The tumor size of liposarcomas was larger than that of leiomyosarcomas; however, the recurrence-free survival was better in patients with liposarcoma than in those with leiomyosarcoma. CONCLUSION: Our results showed the clinical features and prognoses of retroperitoneal and abdominal STS in Japan. Further large-scale nationwide studies are required to clarify the detailed clinical behavior of retroperitoneal and abdominal STS in Japan.

Retroperitoneal tumours--analysis of own clinical material--a six-year retrospective study.

BACKGROUND/AIMS: Primary retroperitoneal tumours and retroperitoneal organs' tumours represent a variety of lesions that require different treatments and have various prognoses. The aim of this study was to present the author's observations of the histological tumors types occurrence and their surgical treatment. METHODOLOGY: One hundred twenty-three cases of retroperitoneal tumours were studied retrospectively in a 6-year period. All cases were investigated for haematological and biochemical parameters. Abdominal ultrasonography, computed tomography or magnetic resonance imaging of abdominal cavity and pelvis were done in the all cases. All cases were subjected to laparotomy with an aim to resect the tumour completely. RESULTS: In the present study we observed primary retroperitoneal tumours like malignant neuroblastoma, paraganglioma, primitive neuroectodermal tumour, cavernous haemangioma and mucinous cystadenoma. Among retroperitoneal organs' tumours pancreatic lesions present the majority of them. There were 6 cases of neuroendocrine pancreatic tumours. We had two cases of retroperitoneal fibrosis in patients with ulcerative colitis. In adrenal glands we observed benign and malignant lesions like pheochromocytoma and fibrosarcoma. All primary retroperitoneal tumours, except two cases of retroperitoneal fibrosis, were an bloc removed. CONCLUSIONS: Primary retroperitoneal tumours in contrast to retroperitoneal organs' tumours occur very rare. Their anatomical location makes early detection difficult and as a result they are usually quite extensive when first detected. The clinical manifestations of all retroperitoneal tumours are not specific, so it causes a lot of difficulties in early diagnosis. This is the main reason that contributes to treatment failure.