Diagnostic imaging of foot mycetomas: A report on two cases.

Mycetomas caused by aerobic actinomycetes are called actinomycetomas. It is primarily localized in subcutaneous tissue but it can spread to different tissue planes including the skin, deep tissues and structures and eventually the bones. We report the cases of 2 patients referred for evaluation of soft tissue masses involving the foot. A 40-year-old male and a 25-year-old male, in both cases MRI was performed to assess the extension, which was later completed by a CT scan. MRI revealed a low intensity matrix that represents fibrosis containing multiple high intensity lesions corresponding to the mycetoma grains. Within some of the lesions a low-intensity focus was identified. This "dot-in-circle sign" on an MRI is a pathognomonic feature of mycetoma. The purpose of this work is to describe the characteristic MRI appearance of foot mycetoma.