Fig. 1

Images of patient #1. A 22-year-old female presented with left limb undergrowth (A, B), a left cavus foot was shorter than the right foot (C). Ultrasound images demonstrated hypoechoic and fusiform enlargement of the left sciatic nerve (diameter: 2.1 cm). The echo intensity of the intraneural soft-tissue elements was similar with the surrounding skeletal muscle (D). An irregular hypoechoic solid lesion was intimately associated with the distally affected sciatic nerve (12.6 × 3.3 cm) (E). MRI demonstrated an abnormal thickening of the sciatic nerve (↑) and a solid mass with irregular borders (△) (F). The patient underwent surgical tumor resection; note that the left sciatic nerve revealed marked thickening (↑) with desmoid-type fibromatosis (DTF) in branches of the nerve (△) (G). A cross-section micrograph (H & E) of the affected sciatic nerve showed endoneurial intercalation of mature skeletal muscle fibers among the peripheral nerve fascicles and diagnosed neuromuscular choristomas (NMC) (H). Beta-catenin immunohistochemical staining shows both aberrant nuclear staining and cytoplasmic staining in the DTF (I)