According to WHO 2020 criteria, LMS diagnosis requires: morphological evidence of smooth muscle differentiation; immunohistochemical positivity for ≥2 smooth muscle markers (SMA, desmin, calponin); exclusion of mimics (e.g., gastrointestinal stromal tumor, malignant peripheral nerve sheath tumor).[5]. This evidence concerns the gene SMN1 and malignant peripheral nerve sheath tumor.