Case Report: Biphenotypic Sinonasal Sarcoma

Abstract Background: Biphenotypic sinonasal sarcoma (BSNS), a rare malignancy with myogenic and neural differentiation, presents diagnostic and therapeutic challenges due to nonspecific symptoms and histologic complexity. Case Presentation: A 58-year-old Bangladeshi male presented with 3 months of nasal obstruction, epistaxis, and headache. MRI revealed a 73×55×56 mm nasopharyngeal mass (T4N1M0, AJCC 8th edition). Histopathology showed spindle cells with nuclear atypia, positive for Desmin, MyoD1, Myogenin and S100, confirming BSNS. Post-R1 resection, residual disease prompted adjuvant therapy. Management: Multimodal therapy included four cycles of ifosfamide/doxorubicin, concurrent chemoradiation (7000 cGy IMRT + weekly chemotherapy), and pazopanib (800 mg/day) for recurrence. Dose reduction (200 mg/day) led to tumor resurgence, necessitating dose escalation (600 mg). Outcome: Initial regression was followed by recurrence at 1 year, managed surgically and with pazopanib. Toxicity-driven nonadherence highlighted the drug’s dose-dependent efficacy. Conclusion: This case underscores BSNS’s aggressive nature and the critical role of multimodal therapy (surgery, chemo-radiation, targeted agents) and vigilant follow-up. Pazopanib demonstrates potential in recurrence, but adherence to optimal dosing is vital. Personalized strategies and multidisciplinary collaboration remain pivotal for improving outcomes in this rare malignancy.