ABSTRACT
Primary tumors originating in the retroperitoneum are extremely uncommon. However, when they occur, the vast majority of these primary retroperitoneal neoplasms are malignant. Primary retroperitoneal tumors can be divided into ( i ) those arising from the mesenchyme (soft tissue sarcomas); ( ii ) those arising from germ cells (extragonadal germ cell tumors); ( iii ) those arising from hematopoietic tissue-lymph nodes (lymphoma).
