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Rhabdomyosarcoma (RMS) is a highly malignant mesenchymal tumor exhibiting skeletal muscle differentiation. It is the most common soft tissue sarcoma of childhood, frequently involving the head and neck region. In the oral and maxillofacial area, rhabdomyosarcoma is particularly important due to its aggressive behavior, rapid growth, and potential to mimic benign inflammatory or reactive lesions.
Definition and Origin
Rhabdomyosarcoma is defined as a malignant tumor composed of primitive mesenchymal cells with the capacity for skeletal muscle differentiation. In the head and neck, RMS often arises from:
- Undifferentiated mesenchymal cells
- Areas lacking mature skeletal muscle
Classification
The World Health Organization classifies rhabdomyosarcoma into major histologic subtypes:
Embryonal rhabdomyosarcoma
= Most common subtype
= Includes botryoid and spindle cell variants
Alveolar rhabdomyosarcoma
= Associated with specific chromosomal translocations
Pleomorphic rhabdomyosarcoma
= Rare
= Occurs mainly in adults
Epidemiology and Etiology
- Most common soft tissue sarcoma in children
- Peak incidence in first decade of life
- Slight male predominance
- Etiology largely unknown
Associated genetic alterations include:
= PAX3–FOXO1 or PAX7–FOXO1 fusion genes (alveolar type)Common Sites of Occurrence
Head and neck rhabdomyosarcoma is categorized into:
- Orbital- Parameningeal (nasopharynx, nasal cavity, paranasal sinuses)
- Non-parameningeal (oral cavity, oropharynx)
Common oral sites include:
- Tongue- Palate
- Buccal mucosa
- Gingiva
- Floor of the mouth
Clinical Presentation
Clinical features are often rapid and aggressive:
- Rapidly enlarging soft tissue mass- Pain or tenderness
- Ulceration or bleeding
- Facial swelling or asymmetry
- Tooth displacement or loosening
- Nasal obstruction or epistaxis (parameningeal tumors)
Lesions may initially resemble abscesses or benign swellings.
Diagnostic Approach
Prompt diagnosis is essential due to aggressive behavior.
Key diagnostic steps include:
- Imaging (MRI/CT) to assess extent and parameningeal involvement- Incisional biopsy
- Histopathologic examination
- Immunohistochemistry and molecular testing
Immunohistochemistry
Tumor cells typically express:
- Desmin
- MyoD1
- Myogenin (highly specific)
- Vimentin
These markers confirm skeletal muscle differentiation.
Histopathological Features
Microscopic findings vary by subtype:
- Embryonal RMS: Primitive mesenchymal cells in loose stroma; rhabdomyoblasts may be presentHigh mitotic activity and necrosis are common.
Differential Diagnosis
Differential diagnoses include:
- Lymphoma- Ewing sarcoma
- Malignant peripheral nerve sheath tumor
- Fibrosarcoma
- Poorly differentiated carcinoma
Immunohistochemistry is critical for accurate diagnosis.
Management and Treatment
Treatment is multimodal and coordinated by oncology teams:
- Combination chemotherapy (mainstay of treatment)- Early referral to specialized centers is essential.
Prognosis
- Prognosis depends on age, tumor site, subtype, and stage- Embryonal RMS has a better prognosis than alveolar RMS
- Head and neck non-parameningeal tumors have more favorable outcomes
- Five-year survival rates range from 60–80% with modern therapy
Role of Dental and Medical Professionals
Dental professionals are often first to encounter oral RMS:
- Recognize rapidly growing pediatric oral masses- Avoid delays in biopsy and referral
- Monitor oral complications of chemotherapy and radiotherapy
- Provide long-term dental and oral care for survivors
For students, rhabdomyosarcoma highlights the importance of pediatric malignancies, molecular genetics, and multidisciplinary care.
Conclusion
Rhabdomyosarcoma is a highly malignant skeletal muscle tumor and the most common pediatric soft tissue sarcoma affecting the head and neck. Early recognition, prompt diagnosis, and aggressive multimodal therapy are critical to improving survival and functional outcomes.