Fat necrosis following inadvertent subcutaneous administration of influenza vaccination

Fat necrosis has been commonly described in the breast as a mimic for carcinoma, however only rare cases of subcutaneous fat necrosis in the extremities have been reported. We show the case of a 41-year-old woman who presented with fat necrosis after a routine influenza vaccination. Subcutaneous fat necrosis was diagnosed based on the ultrasound, radiographic, and magnetic resonance imaging appearance of the lesion. Identification of the characteristic imaging features of subcutaneous fat necrosis may benefit patients by expediting diagnosis and preventing unnecessary biopsies and surgical procedures.