Bizarre parosteal osteochondromatous proliferation of the fifth metatarsal (Nora's lesion)—Case report

We report a case of Nora's lesion (bizarre parosteal osteochondromatous proliferation) of the fifth metatarsal. A 56 year old male, presented with a painless, gradually enlarging swelling over the lateral aspect of his left foot, of 2 years in duration. Plain radiography and MRI showed features consistent with a bizarre parosteal osteochondromatous proliferation of bone (Nora's lesion). The mass was excised and the lesion confirmed histologically. This benign lesion can be confused with malignancy. However, it exhibits a number of key radiographic and histological features, which differentiate it from other benign and malignant processes. It has a strong propensity for recurrence. However this can be decreased by excision of the pseudocapsule, underlying periosteum and removal of any abnormal cortical tissue beneath the lesion.