Ewing sarcoma is an aggressive primary bone tumor predominantly occurring in children and young adults. In the chest wall, it most commonly originates from the ribs, characterized by onion-skin periosteal reaction, large soft tissue component ('iceberg phenomenon'), permeative bone destruction, and t(11;22) translocation. The EWSR1-FLI1 fusion gene is of diagnostic importance. Chest wall Ewing sarcomas account for approximately 7-10% of all Ewing sarcomas and typically reach large sizes at diagnosis. Prognosis depends on tumor size, presence of metastasis, and treatment response; the 5-year survival rate is approximately 65-75% for localized disease and 20-30% for metastatic disease.
Age Range
5-30
Peak Age
15
Gender
Male predominant
Prevalence
Rare
Ewing sarcoma is a small round blue cell neoplasm driven by the t(11;22)(q24;q12) translocation, which results in the fusion of the EWSR1 gene (22q12) with the FLI1 gene (11q24). This fusion protein functions as an aberrant transcription factor driving cell proliferation, differentiation inhibition, and apoptosis resistance. The tumor likely originates from neural crest-derived mesenchymal stem cells. The aggressive permeative growth pattern results from tumor infiltration through the bone cortex along Haversian canals, creating the characteristic 'moth-eaten' appearance. The periosteal reaction occurs as the tumor grows beneath the periosteum, causing repeated elevation-ossification cycles that produce the multilayered 'onion-skin' pattern. In the chest wall, the tumor typically develops a large extraosseous soft tissue component ('iceberg phenomenon'), where the intraosseous component may remain disproportionately small relative to the visible mass.
While the area of destruction within bone is small, the extraosseous soft tissue component reaches very large dimensions — like the small visible tip of an iceberg hiding the massive bulk beneath the water. This phenomenon is the most characteristic feature of chest wall Ewing sarcomas and should always be considered in rib-originating lesions. The iceberg phenomenon results from the tumor rapidly spreading through cortical defects beneath the periosteum and into soft tissue.
Moth-eaten pattern of permeative destruction in the rib cortex. The cortex is involved by multiple small irregular defects without a definable margin of destruction. Tumor infiltration is seen within the bone marrow cavity.
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Permeative bone destruction is observed in the right/left [Xth] rib, with multiple small irregular defects in the cortex in a moth-eaten pattern.
Extraosseous soft tissue mass originating from the rib but disproportionately large compared to the intraosseous component. The mass typically shows homogeneous enhancement but may contain areas of necrosis. Broad contact with the pleural surface may be present with associated pleural effusion.
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At the level of the [Xth] rib, a bone-originating extraosseous soft tissue mass significantly larger than the intraosseous component (approximately _x_x_ cm) is observed (iceberg phenomenon).
Multilayered, regularly spaced periosteal new bone formation on the rib periosteum. At least 2-3 layers are observed in an onion-skin pattern. This finding reflects aggressive but sufficiently slow periosteal elevation and ossification cycles.
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Multilayered onion-skin pattern periosteal reaction is observed along the affected rib.
Homogeneous low T1 signal intensity in the affected rib due to tumoral infiltration with loss of normal bone marrow fat signal. The extraosseous soft tissue component also shows iso- to hypointense signal relative to muscle. T1 sequence is the most sensitive sequence for assessment of bone marrow involvement.
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Homogeneous hypointense signal with loss of normal bone marrow fat signal is observed in the affected rib on T1-weighted sequence, compatible with tumoral infiltration of the bone marrow.
The tumor shows homogeneous high signal on T2-weighted fat-suppressed (STIR) sequences. Peritumoral edema may be observed in surrounding bone marrow and soft tissue. Areas of necrosis may show more prominent high signal. Mass margins are best evaluated on this sequence.
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The mass shows homogeneous high signal on T2-weighted fat-suppressed (STIR) sequences, with peritumoral edema observed in surrounding tissues.
Marked diffusion restriction at high b-values (b=800-1000 s/mm²) with low signal on ADC map. The high cellularity of the tumor (densely packed small round cells, scant cytoplasm) restricts extracellular water diffusion. ADC values are typically in the range of 0.6-0.9 × 10⁻³ mm²/s.
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The mass shows marked diffusion restriction on DWI with low signal on ADC map (ADC: ~___ × 10⁻³ mm²/s), compatible with high cellularity.
The mass shows heterogeneous enhancement on post-gadolinium T1 fat-suppressed sequences. Solid components demonstrate prominent enhancement while areas of necrosis and hemorrhage show no enhancement. Central necrosis is common in large tumors. Peritumoral tissue enhancement may reflect reactive changes.
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The mass shows heterogeneous enhancement on post-contrast series with non-enhancing central necrotic areas; solid components demonstrate prominent enhancement.
Expansile lytic lesion of the affected rib with multilayered periosteal reaction (onion-skin) and large extrapleural soft tissue mass. Bone destruction is seen together with chest wall soft tissue mass. D-sign (extrapleural sign) — obtuse angle formed by inward displacement of the pleura.
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PA chest radiograph demonstrates an expansile lytic lesion at the level of the [Xth] rib with an associated large extrapleural soft tissue mass; periosteal reaction is present.
The primary tumor shows intense FDG uptake (SUVmax typically >5, often >10). Necrotic areas may show decreased uptake. Whole-body PET-CT for staging evaluates bone metastases, lung metastases, and lymph node involvement. Bone marrow metastases are seen as focal increased FDG uptake.
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The mass at the level of the [Xth] rib demonstrates intense FDG uptake (SUVmax: ___). Whole-body assessment for distant metastasis reveals [findings].
Criteria
Most common type. t(11;22)(q24;q12) EWSR1-FLI1 fusion. Small round blue cell morphology, CD99 membranous positivity. Bone involvement dominant. Peak incidence in 10-20 age group.
Distinct Features
Bone origin, permeative destruction, onion-skin periosteal reaction, bone marrow edema
Criteria
Primarily develops in soft tissue, bone involvement is secondary or absent. Carries the same genetic translocation. May occur at older ages. In the chest wall, may originate from intercostal muscles or pleura.
Distinct Features
Soft tissue mass dominant, minimal or absent bone destruction, no periosteal reaction
Criteria
Primitive neuroectodermal tumor (PNET) variant of the Ewing sarcoma family specifically occurring in the chest wall (thoracopulmonary region). May express neural differentiation markers (NSE, synaptophysin, S-100). Clinical and radiological behavior is similar to classic Ewing.
Distinct Features
Thoracopulmonary localization, neural marker positivity, Homer Wright rosette formation, generally larger size
Criteria
Carries t(21;22)(q22;q12) translocation with EWSR1-ERG fusion gene. Accounts for approximately 5-10% of all Ewing sarcomas. Clinical, radiological, and prognostic features are similar to classic EWSR1-FLI1 fusion tumors.
Distinct Features
Radiologically indistinguishable from classic type, diagnosis requires molecular genetics with FISH/RT-PCR
Distinguishing Feature
Osteoid matrix production (cloud-like mineralization), sunburst periosteal reaction, Codman triangle. Unlike Ewing, the tumor produces osteoid. Peak at older age (15-25 years). Rib involvement is rare — prefers metaphysis of long bones.
Distinguishing Feature
May show similar periosteal reaction and bone destruction with fever, leukocytosis, and elevated CRP. However, soft tissue abscess shows rim enhancement (not homogeneous solid mass). Sequestrum (necrotic bone fragment) and involucrum are pathognomonic. Penumbra sign on MRI (T1 peripheral enhancement ring).
Distinguishing Feature
Rib lytic lesion usually small, well-defined with minimal soft tissue component. Beveled edge (inner and outer cortex destroyed at different levels). Usually <20 years. May have multifocal bone involvement. Limited periosteal reaction.
Distinguishing Feature
More homogeneous soft tissue mass, disproportionately large mass relative to bone destruction (similar to Ewing). However, periosteal reaction is usually minimal. Diffusion restriction is marked. Tends to occur at older age. Very high FDG uptake on PET-CT. B-cell markers positive.
Distinguishing Feature
Occurs at younger age (usually <5 years). Primary adrenal/retroperitoneal mass present. Rib metastases tend to be multiple. Urinary catecholamines (VMA, HVA) elevated. MIBG scintigraphy uptake. Calcification more common (80-90% vs <10% in Ewing).
Urgency
highManagement
Multidisciplinary approach: neoadjuvant chemotherapy (VDC/IE regimen — vincristine, doxorubicin, cyclophosphamide / ifosfamide, etoposide alternation) → surgical resection (wide negative margins) or radiotherapy (if unresectable) → adjuvant chemotherapy. Total chemotherapy duration 42-48 weeks. Chest wall resection may require reconstruction with PTFE/polypropylene mesh. In metastatic disease, high-dose chemotherapy + autologous stem cell transplantation is considered.Biopsy
NeededFollow-up
During treatment: response evaluation with MRI after every 2-3 cycles. After treatment completion: every 3 months for first 2 years, every 6 months for years 2-5, then annually after 5 years. Follow-up includes chest CT (lung metastasis), MRI (local recurrence), whole-body bone scintigraphy/PET-CT. Late effects: secondary malignancy (especially in radiation field), cardiotoxicity (doxorubicin), infertility.Ewing sarcoma is a high-grade malignant bone tumor requiring urgent multidisciplinary evaluation. Biopsy planning should be coordinated with the surgical team — incorrect biopsy tract can complicate definitive surgery. Starting with neoadjuvant chemotherapy is the standard approach; histological response (>90% necrosis) is the strongest prognostic factor. In chest wall involvement, post-resection stabilization and reconstruction should be planned.
Ewing sarcoma requires multidisciplinary treatment: neoadjuvant chemotherapy + surgical resection + adjuvant chemotherapy (VDC/IE protocol). Chemotherapy response is the most important prognostic factor (>90% necrosis indicates good prognosis). Radiotherapy is an alternative in non-resectable cases. Prognosis is poor in metastatic disease (lung, bone). 5-year survival is 60-70% in localized disease and 20-30% in metastatic disease. Genetic confirmation (EWSR1 translocation) is required for diagnosis.