Osteosarcoma often is located at the epiphysis or metaphysis of anatomic sites that are associated with maximum growth velocity (distal femur, proximal tibia, proximal humerus), but any bone may be involved. It presents with pain and may be associated with a palpable mass. Because the pain and swelling often are initially thought to be related to trauma, radio-graphs of the affected region frequently are obtained, which usually reveal a lytic lesion, often associated with calcification in the soft tissue surrounding the lesion. While 75% to 80% of patients with osteosarcoma have apparently localized disease at diagnosis, the majority of patients are believed to have micrometastatic disease as well.
Although Ewing sarcoma can occur in almost any bone in the body, the femur and pelvis are the most common sites. In addition to local pain and swelling, clinical manifestations may include systemic symptoms, such as fever and weight loss.
Tissue biopsy is needed for a definitive diagnosis of sarcomas. Selection of the biopsy site is important and has implications for future surgical resection and radiation therapy. Under light microscopy, rhabdomyosarcoma and Ewing sarcoma appear as small, round, blue cell tumors. Osteosarcomas are distinguishable by the presence of osteoid substance.
Immunohistochemical staining for muscle-specific proteins, such as actin and myosin, helps confirm the diagnosis of rhabdomyosarcoma. Two major histologic variants exist for rhabdomyosarcoma: embryonal and alveolar. Embryonal histologic variant is most common in younger children with head, neck, and genitourinary primary tumors. Alveolar histologic variant occurs in older patients and is seen most commonly in trunk and extremity tumors. Alveolar rhabdomyosarcoma often is characterized by specific translocations: t(2;13) or t(1;13). Metastatic evaluation for patients with rhabdomyosarcoma should include a computed tomography (CT) scan of the chest, abdomen, and pelvis; a bone scan; and bone marrow aspiration and biopsy. A lumbar puncture is required in patients with a parameningeal primary site.
Definitive diagnosis of osteosarcoma often is establishedby carefully placed needle biopsy. The presence of osteoidand immunohistochemical analysis confirms the diagnosisof osteosarcoma. The extent of the primary tumor shouldbe delineated carefully with magnetic resonance imaging(MRI) before starting chemotherapy. Osteosarcoma tends tometastasize to the lung, most commonly, and rarely to otherbones. Metastatic evaluation includes a chest CT scan and a bone scan.
The diagnosis of Ewing sarcoma is established with immunohistochemical analysis and cytogenetic and molecular diagnostic studies of the biopsy material. Ewing sarcoma is characterized by a specific chromosomal translocation, t(11;22), which is seen in 95% of tumors. MRI of the primary lesion should be performed to delineate extent of the lesion and any associated soft tissue mass. Metastatic evaluation involves a bone scan, chest CT scan, and bone marrow aspiration and biopsy.
Patients with Ewing sarcoma may be misdiagnosed as having osteomyelitis; children with osteogenic sarcoma often are thought initially to have pain and swelling related to trauma. The differential diagnosis for rhabdomyosarcoma depends on the location of the tumor. Tumors of the trunk and extremities often present as a painless mass and may be initially thought to be benign tumors. Periorbital rhabdomyosarcoma may be misdiagnosed as orbital cellulitis, and other head and neck rhabdomyosarcoma may be confused with chronic infection of ears or sinuses. The differential diagnosis for intra-abdominal rhabdomyosarcoma includes other abdominal malignancies, such as Wilms tumor or neuroblastoma.