Rheumatoid Pseudocyst (Geode) of the Femoral Neck Without Apparent Joint Involvement  BERNARD F. MORREY, M.D.  Mayo Clinic Proceedings  Volume 62, Issue 5, Pages 407-411 (May 1987) DOI: 10.1016/S0025-6196(12)65445-7 Copyright © 1987 Mayo Foundation for Medical Education and Research Terms and Conditions

Fig. 1 Anteroposterior roentgenogram of pelvis of active 66-year-old man with rheumatoid arthritis. The joint space of both hips is preserved. Note large, well-circumscribed, lytic areas in femoral neck and subtle suggestion of presence of a lesion in subchondral region (arrow). Pain was present in left groin. Mayo Clinic Proceedings 1987 62, 407-411DOI: (10.1016/S0025-6196(12)65445-7) Copyright © 1987 Mayo Foundation for Medical Education and Research Terms and Conditions

Fig. 2 Posteroanterior technetium-99m bone scan (image reversed from Figure 1), revealing increased uptake at inferior medial neck of left femur but not in the joint itself or in subchondral region of femoral head. Mayo Clinic Proceedings 1987 62, 407-411DOI: (10.1016/S0025-6196(12)65445-7) Copyright © 1987 Mayo Foundation for Medical Education and Research Terms and Conditions

Fig. 3 Surgical specimen, demonstrating large erosive lesion from margin of articular cartilage (arrows) continuous into femoral neck. Note normal appearance of articular cartilage. Mayo Clinic Proceedings 1987 62, 407-411DOI: (10.1016/S0025-6196(12)65445-7) Copyright © 1987 Mayo Foundation for Medical Education and Research Terms and Conditions

Fig. 4 Histologic preparation, showing fibrous tissue infiltrated by round cells and covered by a mass of fibrin. (Hematoxylin and eosin; x160.) Mayo Clinic Proceedings 1987 62, 407-411DOI: (10.1016/S0025-6196(12)65445-7) Copyright © 1987 Mayo Foundation for Medical Education and Research Terms and Conditions