bubble_chart Overview

In 1921, Ewing first described this primary malignant bone tumor (Ewing's Sarcoma). This highly malignant disease has unique clinical, radiological, and pathological features. It is generally believed to originate from the reticular framework of bone marrow and is less common than osteosarcoma, accounting for approximately 5% of primary malignant bone tumors.

bubble_chart Pathological Changes

The typical lesion erodes the medullary cavity, with tumor tissue being soft and brittle, prone to hemorrhage and cystic degeneration. When confined to the medullary cavity without penetrating the cortex, it is often hard and dense. In the late stage [third stage], the tumor surrounds the affected bone and often metastasizes to the lungs, bones, and lymph nodes.

The histological manifestations are highly inconsistent, making it impossible to diagnose Ewing's fleshy tumor based solely on histology. The final diagnosis requires a combination of radiographic and clinical findings. Typically, its histological features include densely packed small round cells with indistinct borders, vacuolated cytoplasm, and round or oval nuclei embedded within. There is often tissue degeneration, necrosis, and hemorrhage. In such cases, the nuclei are small, and the cell borders are relatively clear. Tumor cells tend to aggregate around vascular spaces, forming pseudorosettes or a peritheliomatous pattern. Contrary to the commonly assumed antagonism, reactive new bone formation is not uncommon, especially in flat bones.

The presence of glycogen in the tumor cell cytoplasm has significant diagnostic value, which can be confirmed by PAS staining. PAS-positive glycogen granules in the cytoplasm indicate sensitivity to amylase digestion. A positive PAS test supports the diagnosis of Ewing's fleshy tumor. Conversely, a negative result does not rule out the diagnosis.

bubble_chart Clinical Manifestations

This disease primarily occurs in adolescents and children, with 80% of patients aged between 10 and 30. It is extremely rare in those under 5 or over 30 years old. Males are more affected than females, and 50% of cases occur in flat bones, most commonly the hip bone, ribs, and scapula, with the spine also being a frequent site. 40% of cases involve long tubular bones, such as the femur, tibia, fibula, and humerus.

The systemic symptoms of Ewing's fleshy tumor are usually quite pronounced, including fever, leukocytosis, anemia, and accelerated erythrocyte sedimentation rate, combined with local manifestations, often closely resembling bone infection. Early complaints include intermittent pain, which later becomes deep and persistently unbearable. As the tumor often erodes through the cortex and penetrates the periosteum, a painful mass can be palpated locally, with the overlying skin appearing tense, congested, and warmer. The prognosis is very poor, with most patients dying within 2 years. 50% die within 1 year of onset, though some reports indicate recurrence after 5–10 years. Early widespread metastasis to the bones and lungs is common, and it is estimated that two-thirds of cases already have metastases at the time of clinical diagnosis.

Due to frequent misdiagnosis of many other diseases as this condition, determining the true 5-year survival rate is challenging. Falk and Alpert reported a 5-year survival rate of 7.9% in 944 cases, while most reports cite 10–15%.

X-ray findings show infiltrative destructive lesions in the medullary cavity of long bones, with mottled or large patchy osteolytic changes being the most prominent. The lesion boundaries are indistinct, and the cortex exhibits irregular defects and destruction. Periosteal reaction occurs early and is abundant. Reactive new bone formation produces Codman's triangle, or the periosteal reaction may appear concentric and layered, resembling onion skin. The former is more common than the latter. Although the diaphysis is the primary site in long bones, metaphyseal origins are not uncommon. Sometimes, a well-defined soft tissue mass shadow is visible outside the bone. The main manifestations include bone destruction and soft tissue masses, with some cases also showing medullary cavity sclerosis.

Early X-ray findings resemble those of osteomyelitis, and the periosteal reactions are also similar, making confirmation by X-ray alone impossible. In the pelvis, the ilium is the most common site, with the tumor appearing as an oval, ring-like, or mottled lytic destruction zone with unclear margins. The tumor may exhibit bone sclerosis accompanied by an onion-skin-like periosteal reaction. This new bone formation is not tumor bone as in osteosarcoma but rather reactive bone formation.

bubble_chart Diagnosis

Histologically, Ewing's fleshy tumor is difficult to distinguish from metastatic neuroblastoma, primary reticular cell fleshy tumor, multiple myeloma, and metastatic bone tumor. As mentioned above, diagnosis requires a combination of clinical, radiological, and histological examinations. In children under 5 years old, differentiation from neuroblastoma is necessary, as the latter shows catecholamines in urine with a positive rate of up to 90%. Metastasis of neuroblastoma to long bones is often symmetrical, and despite extensive bone destruction, the soft tissue mass remains small. The primary tumor can often be detected through intravenous pyelography or paravertebral masses.

For patients aged 20–40, differentiation from reticular cell fleshy tumor is required, while in elderly patients, multiple myeloma and metastatic bone cancer should be considered. The main distinguishing feature is the presence of collagen within the cells of Ewing's fleshy tumor.

The hallmark of osteosarcoma is the formation of tumor bone, which is absent in Ewing's fleshy tumor. However, osteosarcoma with predominantly osteolytic features is difficult to distinguish radiologically from Ewing's fleshy tumor.

bubble_chart Treatment Measures

Due to early and extensive metastasis to bones and lungs, significant bone destruction, and widespread soft tissue involvement, there is currently no satisfactory treatment method or outcome. Although radiotherapy is effective, the recurrence rate remains high, and excessive radiation doses can cause severe side effects. In children before the closure of the epiphyseal plate, radiotherapy can lead to premature closure, resulting in serious growth and developmental disorders. The impact is greater in the lower limbs than in the upper limbs. Therefore, radiotherapy is generally not recommended for children under 12 years old. According to Lew's observations, radiotherapy is suitable for all age groups and various upper limb tumors, while radiotherapy for lower limb tumors is more appropriate for older children and adults. Pathological fractures in weight-bearing bones are an indication for amputation.

bubble_chart Prognosis

Rosen et al. reported that when surgery or radiotherapy was combined with chemotherapy, the 5-year survival rate reached 75%, with a local recurrence rate of 22% and 26% experiencing severe functional impairment. The radiation dose for long bones in the upper limbs typically ranges from 60 to 70 Gy (6000 to 7000 rads).