Sclerosing rhabdomyosarcoma of the gingiva mimicking malignant peripheral nerve sheath tumor: a case report

Background: Spindle cell/Sclerosing rhabdomyosarcoma is the rarest variant of rhabdomyosarcoma, accounting for 5-10% all cases. Pathologically, these tumors can provide a variety features and resemble other tumors, thus often difficult to diagnose. We report case sclerosing gingiva with histomorphology mimicking malignant peripheral nerve sheath tumor. Case Presentation: The patient was 39-years old Balinese male who noticed lump on left gum since 9 months ago. Head CT scan revealed solid mass soft tissue density at lower that extend superiorly laterally, involving parapharyngeal masticator spaces, infiltrated into mylohyoid muscle medial lateral pterygoid muscles, caused destruction mandibular ramus alveolar process maxilla. initial biopsy showed proliferation atypical spindle cells pattern resembling tumor concluded as low-grade Wide excision specimen consists arranged in fascicular foci strap embedded glassy eosinophilic sclerosis matrix. Some parts palisading nuclei. were diffusely positive desmin negative S100. This finally diagnosed rhabdomyosarcoma.Conclusion: Sclerosing should be considered when lesions occur between hyalinized stromal matrix head neck adults. Because wide differential diagnosis, an adequate sampling, careful microscopic examination, immunohistochemistry staining avoid misdiagnosis.