OVIDIU GABRIEL BRATU, ALEXANDRU IONUT CHERCIU, ADRIAN BUMBU, SORIN LUPU, DRAGOS RADU MARCU, FLORENTINA IONITA RADU, MARIA MANEA, CRISTIAN FURAU, CAMELIA CRISTINA DIACONU, DAN LIVIU DOREL MISCHIANU RETROPERITONEAL TUMOURS - TREATMENT AND PROGNOSIS OF TUMOUR RECURRENCE Retroperitoneal tumors, once considered uncommon, have been reported in the last years in such numbers that they cannot be considered anymore a rare condition. Tumor recurrence following surgical excision is quite common and a tumor that was considered originally as benign in many cases can recur as a malignant tumor. The purpose of this paper is to underline the difficulties in terms of establishing a correct diagnosis and a proper therapeutic protocol when facing a retroperitoneal mass of unknown origin, as well as to present the available data regarding prognosis, treatment options and tumor recurrence. Retroperitoneal tumors can be classified as benign or malignant; solid, cystic or both; single or multiple, and of varied histological types. A high percentage of patients with retroperitoneal tumors are discovered in advanced stages, usually seeking medical help for symptoms related to nearby organ compression/invasion. This pathology requires a prompt and adequate multidisciplinary management, in order to achieve disease control and to reduce the recurrence rate. Complete surgical resection is the potential curative treatment for retroperitoneal tumors and it is best managed in high-volume centers, by a multidisciplinary team. Complete oncological tumor resection and tumor grade remain the most important predictors for local recurrence and disease-specific survival. Further research is required in order to define the role of radiotherapy, as well as to discover new biological therapies that target various molecular pathways involved in retroperitoneal cancers.