Langer's axillary arch: a frequent but rarely discussed anatomical variant in the radiologic literature.

The axillopectoral muscle is a rarely discussed variant of muscular anatomy of the axilla, with various clinical implications. We report a case of a 7-year-old girl with multiple genetic and developmental abnormalities who presented with asymmetrical right axillary bulging of unknown etiology. MRI demonstrated a small accessory axillary muscle, known as Langer's axillary arch and/or the axillopectoral muscle. Other than soft-tissue asymmetry, the patient experienced no additional related symptoms. However, this is an important variant to be aware of, as it can easily be discovered on imaging and may be a causative agent for various upper extremity symptoms that may resolve with appropriate recognition and surgical intervention.