We aimed to improve management of extremity low-flow vascular malformations by analyzing the histology and imaging of venous malformations (VMs) not responsive to sclerotherapy.

We reviewed patient records of 102 consecutive patients treated with sclerotherapy for extremity VM in our institution to identify patients who had undergone surgery due to insufficient response. We semi-quantitatively analysed the tissue specimens and compared histological findings to those in preoperative imaging.

The number of patients operated on was 19 (18.6%); 15 of them had lower-extremity intramuscular lesions. The histological pattern of 13 of these 15 lesions corresponded to angiomatosis of soft tissue (AST). All other lesions treated surgically were VMs. The histology of AST was distinctive but magnetic resonance imaging findings often overlapped with those of VM.

AST is easily mixed with intramuscular VM. The differentiation of these two entities has therapeutic importance. We emphasize the role of histology in the differential diagnostics of intramuscular slow-flow vascular malformations.