Pseudo-malignant lesions in Paget's disease of bone.

Two patients with unusual features of Paget's disease are reported. In one patient a circumferential focal and periosteally based mass of Paget's disease presented as a mass lesion superimposed on the sclerotic phase of Paget's disease in the distal femur. Biopsy of the mass showed Paget's disease without neoplasia. The mass has remained unchanged roentgenographically in a 2 year period. In a second patient, a lesion occurred in the mid-portion of the tibia and showed features of the early and radiolucent phase of Paget's disease. In a 4 year period, the lesion has progressed to a more sclerotic phase and to occupy the proximal end of the tibia as well as its mid and lower portions.