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Alveolar rhabdomyosarcoma masquerading as embryonal subtype: the value of modern molecular diagnostic testing
Kian Eftekhari1, Christopher B Chambers, Scott M Goldstein
1*Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania; †Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; and ‡Department of Ophthalmology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, U.S.A.
Insights
A pediatric orbital rhabdomyosarcoma was initially misdiagnosed but correctly identified using molecular genetic testing. This led to targeted therapy, including proton-beam radiotherapy, resulting in long-term remission.
Area of Science:
- Ophthalmology
- Pediatric Oncology
- Molecular Pathology
Background:
- Orbital rhabdomyosarcoma is a rare and aggressive childhood cancer.
- Accurate diagnosis is crucial for effective treatment planning and prognosis.
Observation:
- A 3-year-old presented with conjunctivitis, proptosis, and an orbital mass.
- Initial biopsy suggested embryonal rhabdomyosarcoma, but molecular testing revealed alveolar rhabdomyosarcoma due to the PAX3/PAX7-FKHR gene.
- Magnetic Resonance Imaging (MRI) identified an enhancing orbital mass.
Findings:
- Molecular genetic testing identified the PAX3/PAX7-FKHR chimeric gene, confirming alveolar rhabdomyosarcoma.
- The patient received intensive chemotherapy and proton-beam radiotherapy.
- The tumor significantly shrank, and the patient achieved over 3 years of remission.
Implications:
- Molecular genetic testing is essential for precise diagnosis of orbital rhabdomyosarcoma subtypes.
- Proton-beam radiotherapy offers an effective treatment modality for pediatric orbital tumors.
- Integrated diagnostic and therapeutic approaches improve outcomes for rare pediatric orbital cancers.
Abstract:
A 3-year-old child presented with a history of conjunctivitis in her OS. She had hyperglobus of the OS and a palpable mass in the left inferior orbit. An urgent MRI revealed an enhancing mass in the left orbit. The patient underwent an incisional biopsy with pathologic assessment most consistent with embryonal rhabdomyosarcoma. However, subsequent molecular genetic testing of the biopsy specimen was positive for the PAX3/PAX7-FKHR chimeric gene, indicating the tumor was actually an alveolar rhabdomyosarcoma. The patient received a more intensive chemotherapy regimen and also was treated with proton-beam radiotherapy. After chemotherapy and proton irradiation, the patient's tumor shrank considerably, and she remained in remission at over 3 years of follow up. This patient illustrates the new tools at the disposal of the orbital specialist including molecular genetic testing and proton-beam irradiation to diagnose and treat orbital rhabdomyosarcoma.
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