Painful calcifying aponeurotic fibroma

A 22-year-old man presented with a firm, tender, 2.5 × 2.5 cm skin-colored nodule with well-defined margins on the mid-plantar aspect of his left foot [Figure 1a]. The overlying skin was unremarkable and non-adherent to the mass which was fixed to the underlying soft tissue structures. The lesion had gradually enlarged over the last 14 years and was painful. There was history of a burn injury at the same site, two months prior to the onset of the lesion. The differential diagnoses of nodular fasciitis and post-traumatic neuroma were considered.