Rare case of retroperitoneal tumor with unusual evolution

The retroperitoneum can host a wide spectrum of pathologies, including a variety of rare benign tumors and malignant neoplasms that can be either primary or metastatic lesions, whose correct diagnosis can be a challenge for the medical team and whose approach is often complex. We present the case of a patient diagnosed in June 2011, as a result of non-specific abdominal symptoms, with a small retroperitoneal mass with cystic appearance, whose affiliation could not be established. The evolution of this tumor was stable during the 3.5 years of clinical, biological and imaging follow-up, until January 2015 when the patient experienced neurological symptoms of lumbar nerve root compression which could have been associated with the increase in size of the retroperitoneal tumor. The therapeutic management was surgical tumor resection, and histopathology was suggestive for a pseudo-cyst, whose etiology remained unspecified. The peculiarity of the case is represented by the long silent evolution of a retroperitoneal mass, in which the association of neurological symptoms have posed problems of differential diagnosis, and in which the tumors etiology and sudden growth in size haven’t been elucidated by the histopathological examination, where no cellular structures able to guide the diagnosis were detected. The curative treatment in these cases remains complete surgical resection of the tumor.