Fig. 2

MRI and surgical resection of a FAVA in calf. a, Axial T1-weighted MRI. Both extensor longus digitorum and tibialis anterior muscle were diffusely infiltrated by heterogeneous mass with high fatty signal and low signal. b, Axial fat-saturated T2-weighted MRI revealed the lesion containing high fluid signal, the saturated fatty signal and other low signal. Note displaced and atrophied extensor hallucis longus, musculi peronaeus longus, and musculi peronaeus brevis, and the involved and thickened muscular fascia. c, Physical examination revealed no limitation of plantar flexion of the hallux, and limited plantar flexion of the second - fifth toes, suggesting extensor longus digitorum involvement. d, Operative findings. The deep fascia of extensor longus digitorum became thickened by fatty tissue and tufted frogspawn-like venous lakes infiltration. e, Dense, scarred fibroadipose tissue and venous anomaly infiltrated extensor longus digitorum and replaced the normal muscular pattern. f, After extensor longus digitorum and tibialis anterior muscle resection, tendon transfer was performed to reconstruct the dorsiflexion funtion of ankle. g, The appearance of sutured incision after placement of a vacuum drainage tube. h and i (HE staining, ×100), Histopathologic examination demonstrated excessive fat and fibrous tissue with abnormal medium-sized veins in deep fascia. Anomalous venous channels, fibrous and adipose tissue infiltrated the skeleton muscle and fascia. Abundant adipose and venous clusters, abnormal small-sized and medium-sized veins, and dense fibrous tissue were demonstrated, the latter concentrating around venous spaces. Thick-walled muscularized vasculars can be observed focally