Original ArticlesSubarticular Inflammatory Pseudoabscesses A Pathologic Study With Clinical CorrelationZhang, Lingxin MD*,†; Mirza, Serene Z. BSc*; DiCarlo, Edward F. MD* Author Information *Department of Pathology and Laboratory Medicine, Hospital for Special Surgery †Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, NY Presented in part at the 108th Annual Meeting of the United States and Canadian Academy of Pathology, March 18, 2019, National Harbor, MD. Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Lingxin Zhang, MD, Department of Pathology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10021 (e-mail: [email protected]). The American Journal of Surgical Pathology: May 2020 - Volume 44 - Issue 5 - p 633-640 doi: 10.1097/PAS.0000000000001440 Buy Metrics Abstract Abnormal accumulation of neutrophils in a subarticular bone usually raises the concern for osteomyelitis or septic arthritis, a disabling and potentially life-threatening medical condition. At the pathology department of a specialized orthopedic institute, we observed a distinct pattern of subarticular inflammation mimicking infection characterized by collections of neutrophils, macrophages, and fibrin in pseudocystic spaces of variable size and extent in the superficial subarticular bone not accompanied by granulation tissue or necrosis. We coined the term “inflammatory pseudoabscess” to describe these accumulations. From 1997-2015, we reported inflammatory pseudoabscesses in 157 primary arthroplasty/osteotomy specimens from 143 patients without penetrating trauma or hardware in the affected joint. The predominant gross and histologic features were those of destructive/inflammatory joint disease, including lymphoplasmacytic synovitis (95.3%), subchondral osseous chronic inflammation (80.3%), exudative synovitis (58.0%), synovial pannus (52.0%), and marginal erosions of articular cartilage and/or subarticular bone (43.3%). Clinical information was available in 137 (95.8%) patients, 107 (overall: 74.8%) of whom had preoperatively or postoperatively diagnosed inflammatory arthropathy, most commonly rheumatoid arthritis. The remaining 30 (overall: 21.0%) patients had no documented inflammatory disorders, but some had bilateral or multijoint arthropathy, hands/feet involvement, lymphoplasmacytic synovitis, ulcerative colitis, or family history of inflammatory arthropathy. There was no documented infection-associated implant failure. We believe that inflammatory pseudoabscess represents an intraosseous manifestation of noninfectious inflammatory disorders of joints. This feature should be recognized by pathologists and used to suggest further clinical evaluation for undiagnosed inflammatory joint diseases. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.