Most cases represent non-functioning tumors.
Common presenting signs and symptoms include large abdominal mass, sometimes palpable, pain, weakness, lethargy and fever. The tumors usually attain a large size prior to diagnosis and typically weigh over 100 grams, often exceeding 1,000 grams. The large size is thought to be due to the retroperitoneal location of the tumor producing symptoms only late in the course of disease, especially if the tumor is non-functioning. When the tumor is functioning, it is believed that the enzymatic activity of the cells is not sufficient to produce symptoms until late in the disease process. This also helps to explain the high incidence of distant metastasis at the time of initial presentation.