Fig 2.

A 3-month-old boy with a reddish-blue infra-auricular nodule that had been noticed for 2 days (patient 3). A, Transverse sonographic image reveals a hypoechoic solid mass. The mass was mistaken for adenopathy. B, Axial contrast-enhanced CT image shows a sharply circumscribed subcutaneous mass (arrow) that also involves the skin. The mass is isoattenuating with muscle and has no distinguishing characteristics other than its location. The lack of calcification is unusual for pilomatrixoma, which is the most common tumor in this location in children. The lack of necrosis or parotid space adenopathy is atypical for nontuberculous mycobacterial infection, which is the most common infection in this location.