Ewing’s sarcoma is he second most common primary malignant tumor of bone found in children.Ewing Sarcoma is an uncommon primary malignant bone tumor.It has been named after Ewing, who first described it in 1921.
Ewing sarcoma has a characteristic predilection for an age group between 10 and 15 years. The tumor is more common in boys than in girls.
Ewing’s sarcoma can occur in the innominate bone, femur, humerus, fibula, clavicle, or tibia. In the long tubular limb bones, the lesion is situated in the diaphysis rather than in the metaphysis. Rib, scapula, or vertebra are infrequent sites.
Rarely it occurs in the bones of the hands or feet.
On gross inspection the neoplasm appears as a whitish-gray soft mass that arises in the marrow spaces of the interior of the affected bone. Necrotic and hemorrhagic areas in the tumor are frequent. Anatomic involvement of the bone is always much more extensive than is apparent in the radiograms.The tumor is not encapsulated
The tumor destroys and replaces the involved bone, elevates the periosteum and often perforates it. When this happens a large mass extends beyond the bony boundaries. In case of involvement of inominate bone, the soft-tissue mass can protrude into the pelvis and abdomen.
Histologic examination reveals compact sheets of small polyhedral cells with pale cytoplasm and ill-defined boundaries. The nuclei are uniform, round or oval in shape, and contain scattered areas of chromatin. There are a multitude of thin-walled vascular channels among a scanty stroma. The cytoplasmic material is PAS positive and diastase digestible. Occasional rosette or pseudo-rosette formations may be present.
These cytologic findings simulate those of neuroblastoma or malignant lymphoma.
Extensive necrosis and degenerative changes may also confuse the picture. The tumor, because of involved hemorrhage may show a reparative inflammatory reaction, which may mislead to diagnosis of infection.
A distinguishing histochemical finding is the presence of glycogen in the cells of Ewing’s sarcoma. In reticulosarcoma, there is no glycogen.
Clinical Presentation
Symptoms depend on the site of the lesion but pain is the most commmon presenting complaint.
**When a rib is involved, pleural effusion may be noted.
**Stiffness of the adjacent joint is common in cases of long bones.
**The nerve roots may be involved in spine.
**Rectal and urinary complaints may occur when the neoplasm is located in an innominate bone.
**On occasion the presenting feature is a pathologic fracture.
One can usually palpate a tumor mass that is tender on pressure. It is usually larger than the bony lesion depicted in the xray.
Malaise, lethargy, and progressive weight loss develop early in the course of the disease.
Radiographic Findings
On plain xrays, mottled rarefaction of the spongiosa with permeation of the overlying cortex is the principal finding. The bone may show expansion and periosteal new bone formation.
The laminated onion-peel appearance is common but not specific for Ewing’s sarcoma.
A soft-tissue mass overlying the area of bone destruction is a common finding and indicates bone perforation.
The lesion is diaphyseal in location in long bones and in spite of extensive involvement, the pathologic fractures are rare.
Differential Diagnoses
- Eosinophilic granuloma
- Reticulum-cell sarcoma
- Malignant lymphoma
- Osteolytic osteogenic sarcoma
- Metastatic neuroblastoma
- Leukemia
- Osteomyelitis.
Staging
Staging Ewing’s sarcoma is by the extent of involvement at the time of presentation.
Stage I - solitary and intraosseous.
Stage II – solitary and extraosseous
Stage III – multicentric but confined to the affected bones.
Stage IV – Ewing’s sarcoma with distant metastases at the time of presentation.
Scintigraphy with technetium-99m, Linear tomography and computed tomography will demonstrate the details of the lesion, the presence or absence of cortical destruction, the extent of the intraosseous involvement, and the degree of extraosseous soft-tissue spread.
Magnetic resonance has, is very effective in delineating the extent of the tumor.
Diagnosis
Definitive diagnosis is made from histologic study of tissue sections obtained by biopsy. Open biopsy should be preferred over needle biopsy which should be reserved for unaccessible areas.
Treatment
The tumor is radiosensitive, and irradiation markedly reduces but cannot completely eradicate the tumor.The tumor responds to chemotherapy which should be administered in all cases.
The most effective methods of treatment, providing the best changes for complete surpression of the tumor, are a combination of
- Chemotherapy and irradiation
- Chemotherapy and surgical ablation
- Chemotherapy, irradiation, and surgical ablation. (only in rare cases)
Indications for surgical Removal
- Bone that can be removed without great functional disability)
- A bone difficult or impossible to treat
- A tumor that does not respond to irradiation
- Tumor in close proximity to the physis of a long bone in a young child where irradiation can result in growth arrest and gross limb length disparity.
In other instances chemotherapy combined with irradiation is the preferred method of treatment.
In case of pathologic fractures, treatment consists of internal fixation and bone grafting.
With metastases, chemotherapy is continued.
With the advent of combined chemotherapy and radiotherapy and skeletal adjuvant surgery, the prognosis is greatly improved.
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