Iliopsoas bursitis-an unusual presentation of metastatic bone disease.

Diagnostic uncertainty concerning the nature of an enlarging inguinal mass in an elderly male with a short history of hip pain was resolved by a combination of ultrasound and magnetic resonance imaging (MRI). Subsequent investigations showed that the enlarged iliopsoas bursa, which contained a number of atypical cells, was an unusual presenting feature of a destructive metastatic lesion in the right hip.