Adult Orbital Embryonal Rhabdomyosarcoma: Diagnostic Ambiguity and Surgical Salvage in a Multidisciplinary Context

Background: Adult orbital embryonal rhabdomyosarcoma (ERMS) is an exceedingly rare malignancy often misdiagnosed as lymphoma due to overlapping clinical and histopathologic features. Early and accurate diagnosis, supported by immunohistochemistry, is essential for guiding appropriate management. Case Presentation: A 37-year-old woman presented with progressive right-sided proptosis and ocular discomfort, ultimately leading to globe rupture. Orbital MRI revealed a heterogeneous intraocular mass with local invasion. Emergency enucleation was performed, and initial histopathology suggested large B-cell lymphoma. PET-CT demonstrated hypermetabolic lesions in the orbit, lungs, adrenal glands, and cervical lymph nodes. The patient received three cycles of CHOP chemotherapy without improvement. Further immunohistochemical analysis revealed positivity for desmin, focal myogenin, and MyoD1, establishing a diagnosis of ERMS. Given rapid progression and neurological risk, an extended orbital exenteration was performed. Final histology confirmed ERMS with >80% necrosis and clear surgical margins. Adjuvant radiotherapy was administered postoperatively. Conclusion: This case highlights the diagnostic complexity of adult orbital ERMS and emphasizes the pivotal role of immunohistochemistry. Surgical salvage, when guided by multidisciplinary consensus, may be a viable option even in suspected systemic involvement.