Low-Grade Sinonasal Sarcoma With Neural and Myogenic Features: A Recently Discovered Entity With Unique Features and Diagnostic Challenge.

Low-grade sinonasal sarcoma with neural and myogenic features is an entity recently described in the literature. Little is known about its etiopathogenesis, natural history, or optimal treatment. In fact, it has relatively unique findings: it has a distinctive cytogenetic signature, and it expresses both smooth muscle actin and S100 protein. However, its diagnosis is challenging on biopsies showing negative staining for these 2 markers. The differential diagnoses include fibrosarcoma, malignant peripheral nerve sheath tumors, and other benign and malignant lesions. A complete resection, with or without radiotherapy, is required because this lesion appears to be locally aggressive. However, the clinical outcome seems to be good. Low-grade sinonasal sarcoma with neural and myogenic features merits classification as an independent tumor in the next World Health Organization classification of head and neck tumors. Reports of additional cases are required to support its unique classification.