Ewing's sarcoma often prompts patients to seek medical attention due to pain. Symptoms can include swelling and pain in the tumor region, as well as intermittent fever, loss of appetite, and weight loss. If the tumor affects the lungs, pleural effusion (fluid accumulation in the lung membranes) and shortness of breath may occur. If the spinal cord is involved, neurological findings such as numbness, tingling, or weakness due to nerve compression may manifest. Ewing's sarcoma is sometimes discovered incidentally when a bone, weakened by the tumor, breaks easily after a fall or accident. Conditions that need to be differentiated during diagnosis include other malignant bone tumors and bone infection (osteomyelitis); osteomyelitis can also present with redness and fever. In approximately 25% of cases, the cancer has already spread to other parts of the body at the time of diagnosis. The most common sites of spread are the lungs, bones, and/or bone marrow. Less common areas of metastasis include the central nervous system and lymph nodes.