The doughnut sign in patients with multiple myeloma.

Bone lesions with a ring-shaped appearance (the doughnut sign) have been encountered during routine reporting of bone scintigrams performed on patients with multiple myeloma. Such a ring-shaped appearance has been revealed in four (8%) of the last 50 bone scintigrams performed on patients with myeloma at the Royal Marsden Hospital. In contrast, a review of the last 300 bone scintigrams performed on patients with bone metastases failed to reveal any such ring-shaped appearance. Examination of the case notes and radiographs of the multiple myeloma patients did not reveal any correlation between the presence of the ring-shaped appearances and the histology, biochemistry, treatment, or course of the disease nor were any specific radiographic features noted. Three of the four patients have had local radiotherapy to the sites of the lesions. We conclude that the ring-shaped appearance on bone scintigrams is usually related to myelomatous bone lesions, particularly following local radiotherapy to these lesions. The reason for this appearance in three of the four scintigrams may be the stimulation of vascularity and osteoblastic activity around the periphery of the myelomatous lesions by the response of the lesions to radiotherapy.