Massive Pelvic Chronic Expanding Hematoma Requiring Differential Diagnosis From Pseudotumor After Revision Total Hip Arthroplasty

CASE: We present 2 cases of chronic expanding hematoma (CEH) mimicking pseudotumors after revision total hip arthroplasty (THA) with metal-on-polyethylene bearings. Both patients developed large pelvic masses with imaging findings suggestive of adverse local tissue reactions. CEH was confirmed surgically and histologically. Partial resection and implant revision improved symptoms; 1 case also involved metal debris. CONCLUSION: These cases highlight the diagnostic challenge in distinguishing CEH from pseudotumors and emphasize the importance of considering CEH in the differential diagnosis of pelvic masses after THA.