Dermatologists should be aware of a tear of the rectus femoris muscle presenting as a subcutaneous mass to defer biopsy and properly refer for imaging and orthopedic evaluation.
A healthy young woman presented with a 2-month history of an enlarging right anterior thigh subcutaneous mass. The lesion was asymptomatic but had grown significantly. She ran recreationally and recalled no trauma to the area. A 4-cm firm subcutaneous mass was palpated with no overlying epidermal change (Figure 1). The mass was palpable with right hip flexion and disappeared on right hip extension. Complete blood cell count test results, lactate dehydrogenase test results, and plain-film radiography of the right femur were normal. The patient was referred for radiologic imaging and orthopedic evaluation.