Intramuscular vascular malformations of an extremity: findings on MR imaging and pathologic correlation

Objective. To analyze the findings of intramuscular vascular malformations of an extremity on MR imaging and to correlate these findings with histopat hologic examination. Design and patients. The findings on MR imaging and the medical records of 14 patients with an intramuscular vascular malformation of the extremity we re retrospectively studied. All patients underwent surgical excision. Diagn oses were based on the results of pathologic examination. Findings on MR im aging were noted and correlated with the histopathologic findings. Results. Intramuscular vascular malformations of an extremity showed multi- septate, honeycomb, or mixed appearance on MR imaging. Multiseptate areas c orrelated with dilated and communicating vascular spaces with flattened end othelium. Honeycomb areas corresponded to vascular spaces with inconspicuou s small lumina and thickened vascular walls. Areas of increased signal inte nsity on T2-weighted images were found in all intramuscular vascular malfor mations. Infiltrative margins were more commonly seen in intramuscular lymp haticovenous malformations. Adherence to neurovascular structures and orien tation of the lesion along the long axis of the affected muscle were more c ommonly seen in intramuscular venous malformations. Conclusions. Intramuscular vascular malformations showed either a multi-sep tate, honeycomb, or mixed appearance, reflecting the size of the vascular s paces and the thickness of the smooth muscles of the vessel walls. Predicti on of the subtype of an intramuscular vascular malformation of an extremity on MR imaging seems to be difficult, although there are associated finding s that may be helpful in the differential diagnosis of each subtype.