MD2B - Pediatric Oncology: Ewings Sarcoma

Overview

Ewings sarcoma is a cancerous tumor that arises in bone or soft tissue. Histologically, it is a type of small blue round cell tumor along with lymphoma, rhabdomyosarcoma, and neuroblastoma. It is the second most common primary bone tumor in children (after osteosarcoma), but is the most lethal form of bone cancer observed in children. It most frequently occurs in the long bones of the extremities but can also arise in the pelvis, ribs, skull, and scapula (shoulder blades). Unlike osteosarcoma which usually arises from the metaphysis (portion of the bone where cartilage is being added), Ewings sarcoma most commonly arises from the diaphysis (mid-shaft of the bone).

Ewings sarcoma can be seen in children of all ages, but it most frequently occurs in adolescents. Approximately 300 new cases are diagnosed each year in the United States. Ewings sarcoma is more common in males than females, and is seen in Caucasians more frequently than in Asians. It is rarely seen in African Americans. Over 80% of these tumors have a classic chromosomal translocation between chromosomes eleven and chromosome twenty-two (t(11,22)(q24;q12)), allowing them to be more easily identified and diagnosed. 25% of children with Ewings sarcoma have primary metastases to the lungs, bone marrow, or to other bones.

Symptoms

Ewings sarcoma most frequently presents with pain, swelling, or limitation of movement at the site of the tumor. Less frequently, a fracture can occur following minimal trauma at the tumor site. Some children may also present with fever, fatigue, weight loss, or decrease in appetite. If the tumor is located near the spinal cord or around a nerve fiber, weakness, numbness, tingling, paralysis, or bladder incontinence (loss of bladder control) may occur.

Differential Diagnosis

Ewings sarcoma may initially be misdiagnosed because there are many common problems that can result in limb pain in a child. Often, the pain is first attributed to growth pain, a sports injury, tendonitis (inflammation of a tendon), coxsitis (inflammation of the hip) or as osteomyelitis (infection of a bone). In young children, neuroblastoma should also be considered in the differential. A urinalysis can sometimes help to distinguish between these two types of cancer as urine catecholamines (specific hormones) will often be elevated in neuroblastoma but will be normal in Ewings sarcoma.

Diagnosis

A physician will perform a careful physical examination, schedule imaging tests, and order laboratory tests to help distinguish Ewings sarcoma from other bone conditions.

Imaging studies

• x-rays: a diagnostic test using energy beams to produce images of internal tissues, bones, and organs. In Ewing's sarcoma a lytic bone lesion is observed with a surrounding periosteal reaction. This is often described as an "onion skin" appearance.
• bone scans: a diagnostic test using nuclear imaging to appreciate bone degeneration, inflammation, or tumor
• magnetic resonance imaging (MRI): a diagnostic test using large magnets and radiofrequency signals connected to a computer to produce detailed images of structures within the body including the spinal cord and nerve fibers. Ewing's sarcoma appears as a large soft tissue mass.
• CT or CAT scan: a diagnostic imaging test that uses x-rays and computer technology to produce cross-sectional images of slices of the body. Ewing's sarcoma appears as a large soft tissue mass.

Tissue samples

Samples from the primary tumor and from the bone marrow will be removed by inserting a needle into the tumor and into the hip bones. These samples will be examined under the microscope to look for cells that appear abnormal or cancerous.

Treatment

Before the development of effective chemotherapy, surgery alone was used to treat Ewing's sarcoma and the 5-year survival rates were dismally below 20%. Patients most frequently developed metastases within 2 years. The addition of chemotherapy and radiation therapy to treatment protocols has greatly improved overall 5 year survival. Those patients who present with disease that is localized at time of diagnosis have a 70% 5 year survival. Patients who have metastatic disease have lower survival rates.

Once a diagnosis of Ewing's sarcoma has been confirmed, patients will first be treated with chemotherapy to shrink the tumor and to prevent new tumors from forming. Patients will then undergo surgery in an attempt to remove all areas of remaining tumor. Depending on the site and stage of the tumor, radiation therapy may also be utilized in treating Ewing's sarcoma.

Prognosis

Patients with small tumors that have not spread beyond their primary location have a 75% survival rate. Those with tumors located distally (at the far end of bones) have the best prognosis. Patients with pelvic tumors and those whose cancer has already spread at the time of diagnosis have poorer prognoses, and only 30% experience long term survival.