Ultrasound and magnetic resonance imaging (MRI) assessment of piezogenic papules: A report of three cases.

Piezogenic papules (PP) are protrusions of fat that form within the subcutaneous tissue, which are typically found on the heels. We herein describe the ultrasound (US) presentation (topography, echogenicity, shape, dynamic reducibility, and power Doppler activity) and magnetic resonance imaging features (topography, signal, and shape) of PP in three female patients who were referred to our institution for evaluation of soft tissue nodules of the heel. Then, we discuss the anatomy of the heel fat pad and its implication in the pathophysiology of PP. Because PP consist of herniations of subcutaneous fat from deep macrochambers to superficial microchambers through focal defects in the fibroconjunctive capsule of the heel fat pad, dynamic US can demonstrate the reducibility of PP under probe compression and therefore allows easy differentiation from other soft tissue tumors.