Rhabdomyosarcoma (RMS) is the most common primary orbital malignant tumor in childhood and represents the orbital form of soft tissue sarcomas. The embryonal subtype is the most common histological type (70-90%). It typically presents with rapid-onset proptosis in children aged 2-5 years, and the clinical course is aggressive. The superomedial orbit (upper inner quadrant) is the most common location. The tumor may cause bone destruction and extend to paranasal sinuses and intracranial space. With modern chemotherapy and radiation therapy protocols, 5-year survival has reached 90-95%. Early diagnosis and treatment are critically important because delay increases the risk of local invasion and distant metastasis.
Age Range
2-15
Peak Age
7
Gender
Male predominant
Prevalence
Rare
Rhabdomyosarcoma is a malignant tumor originating from skeletal muscle precursor cells (rhabdomyoblasts); however, tumor development in areas without normal skeletal muscle such as the orbit suggests origin from pluripotent mesenchymal stem cells. In the embryonal subtype, the PAX-FOXO1 fusion gene is generally negative, while in the alveolar subtype, PAX3-FOXO1 or PAX7-FOXO1 fusion genes are positive and associated with more aggressive biological behavior. Tumor cells show rapid proliferation and directly invade surrounding tissues, causing bone destruction, extension to sinuses and intracranial space. Homogeneous enhancement reflects the tumor's dense vascularization and active angiogenesis. Bone destruction results from osteoclast activation through matrix metalloproteinase (MMP) production by tumor cells. The rapid growth pattern reflects the tumor's high mitotic index and short cell cycle time.
A homogeneously intensely enhancing orbital mass with bone destruction developing within days to weeks with rapid proptosis in a child aged 2-5 years is the most typical presentation of rhabdomyosarcoma.
A homogeneously intensely enhancing orbital mass is seen on contrast-enhanced CT, most commonly located in the superomedial orbit (upper inner quadrant). Mass margins may be well-defined or irregular; aggressive margins suggest paranasal sinus or intracranial extension. Bone destruction is seen in approximately 40-50% of cases, particularly affecting the orbital roof, medial wall, or sphenoid bone. Calcification is rare (less than 10%), and when present, retinoblastoma or other diagnoses should be considered. Enhancement is homogeneous, and necrotic areas are rarely seen. Globe displacement varies depending on tumor location.
Report Sentence
A homogeneously intensely enhancing mass in the superomedial orbit is noted on contrast-enhanced CT, accompanied by bone destruction of the orbital roof, consistent with pediatric orbital rhabdomyosarcoma.
Rhabdomyosarcoma shows intermediate-to-slightly hyperintense homogeneous signal on T2-weighted images. The homogeneous cellular structure of the tumor creates homogeneous signal distribution on T2. Areas of necrosis or cystic degeneration show more prominent T2 hyperintensity. Peritumoral edema may be seen as a T2 hyperintense halo. Fat-suppressed T2 sequences clearly distinguish the tumor from orbital fat and optimally demonstrate tumor boundaries. Extension to paranasal sinuses and intracranial component are evaluated on T2 sequences.
Report Sentence
An orbital mass with intermediate-to-slightly hyperintense homogeneous signal is noted on T2-weighted images, and rhabdomyosarcoma should be considered in the differential diagnosis.
Rhabdomyosarcoma shows intense homogeneous enhancement on contrast-enhanced fat-suppressed T1-weighted images. The degree of enhancement reflects the tumor's dense vascularization. Perineural spread (especially along trigeminal nerve branches) may be seen as enhancing linear structures and is critical for intracranial extension assessment. Meningeal enhancement indicates intracranial involvement. Necrosis areas are distinguished as non-enhancing hypointense foci. Fat suppression eliminates orbital fat signal, highlighting the enhancement pattern.
Report Sentence
An intensely homogeneously enhancing orbital mass is noted on contrast-enhanced fat-suppressed T1-weighted images and should be evaluated for perineural spread and intracranial extension.
Rhabdomyosarcoma shows diffusion restriction on DWI and appears hyperintense at high b-values. Low signal on ADC map is noted. Diffusion restriction reflects the tumor's high cellularity. ADC values are used in treatment response monitoring; increase in ADC values (decrease in cellularity) is expected after successful chemotherapy. Necrotic areas do not show diffusion restriction and show high ADC values.
Report Sentence
Diffusion restriction in the orbital mass is noted on DWI, consistent with a highly cellular malignant tumor.
Rhabdomyosarcoma appears as a solid mass with markedly increased vascularity on color Doppler ultrasonography. On B-mode, the mass has hypoechoic-to-medium echogenicity with heterogeneous structure. Increased arterial flow and low resistance index reflect the tumor's active angiogenesis. Calcification is rare. Ultrasonography is useful for rapid bedside evaluation but MRI is essential for complete assessment of tumor extension.
Report Sentence
A solid orbital mass with markedly increased vascularity is noted on Doppler ultrasonography, consistent with a hypervascular malignant tumor.
Criteria
Most common subtype (70-90%). Usually 2-5 years. PAX-FOXO1 fusion negative. Better prognosis.
Distinct Features
5-year survival 90-95% with standard chemotherapy + radiation. Orbit is a prognostically favorable site. Homogeneous imaging features.
Criteria
Less common (10-20%). PAX3-FOXO1 or PAX7-FOXO1 fusion positive. More aggressive biological behavior and worse prognosis.
Distinct Features
Higher risk of metastasis. Requires intensive chemotherapy regimens. Imaging may show more heterogeneous and necrotic appearance.
Criteria
Polypoid subtype of embryonal. Usually grows from mucosal surfaces (conjunctiva). 'Grape cluster'-like polypoid growth pattern.
Distinct Features
Good prognosis. May present as conjunctival mass. Clinically easy to identify.
Distinguishing Feature
Sinusitis accompanies orbital cellulitis, fever and leukocytosis are present, subperiosteal abscess shows crescent-shaped collection. RMS shows solid mass and bone destruction. Response to antibiotic treatment favors cellulitis.
Distinguishing Feature
Capillary hemangioma is seen in infants (under 1 year) and shows spontaneous involution. Flow voids may be seen. RMS is seen at 2-5 years, causes bone destruction, and shows rapid progression.
Distinguishing Feature
Orbital lymphoma is seen in elderly adults (RMS in children), shows moulding pattern, and does not cause bone destruction. Lymphoma is painless and slow; RMS grows rapidly.
Distinguishing Feature
In children, orbital metastasis most commonly originates from neuroblastoma. Urine catecholamines are elevated and abdominal primary mass is present in neuroblastoma. RMS is a primary orbital tumor. Neuroblastoma metastasis usually presents with bone lesions (periorbital ecchymosis — raccoon eyes).
Urgency
emergentManagement
medicalBiopsy
NeededFollow-up
Tedavi sırasında 6-8 haftada bir MR ile tümör yanıt değerlendirmesi. Tedavi sonrası 3-6 aylık MR takip, en az 5 yıl. Geç relaps açısından uzun vadeli takip.Rhabdomyosarcoma diagnosis requires histopathological confirmation by biopsy. Treatment protocol (IRS/COG study groups) includes chemotherapy (vincristine + actinomycin D + cyclophosphamide — VAC regimen) + radiation therapy (45-50 Gy) combination. Surgery is generally not recommended as primary treatment; radical surgery leads to cosmetic and functional morbidity, and equivalent oncological outcomes are achieved with chemotherapy + radiation therapy. Orbit is a prognostically favorable site, and the embryonal type has better prognosis. With modern treatment, 5-year survival has reached 90-95%. Staging workup (CT chest, PET-CT, bone marrow biopsy) should be performed to exclude metastatic disease.
Urgent biopsy and treatment initiation required. Combined chemotherapy+radiotherapy achieves >90% survival. Staging (regional lymph node + distant metastasis) is necessary.