Bone scalloping refers to a particular pattern of localized bone erosion appearing as multi-curved, sharply marginated lucencies on radiographic images. This imaging finding indicates an indolent bone remodeling process, which can be caused by benign or malignant conditions. We describe a case of the bone scalloping caused by a giant arachnoid (pacchionian) granulation. Such granulations may simulate malignant osteolytic lesions on radiographic images and cause diagnostic challenges especially in patients with pre-existing malignancy such as plasmacytoma.

Keywords: Arachnoid granulation; Bone scalloping; Osseous lytic lesion; Myeloma; Plasmacytoma