Diagnostic Dilemma of Cortical Erosion in Bizarre Parosteal Osteochondromatous Proliferation: A Systematic Review and Pooled Cohort Analysis of 323 Cases

Background: Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora’s lesion, is a rare, benign, surface-based bone lesion. Although cortical preservation is a traditional diagnostic hallmark, recent evidence suggests cortical erosion may occur, potentially mimicking malignancy. Methods: We conducted a systematic review and pooled cohort analysis of 323 cases from 74 studies following PRISMA 2020 guidelines. A search of PubMed/MEDLINE and Google Scholar identified 1,047 records. Using a Mantel-Haenszel fixed-effect model to provide Level II evidence, we compared recurrence rates between simple excision (n=200) and en-bloc resection with adjuvant high-speed burr curettage (n=123). Results: BPOP is locally aggressive. High recurrence after simple excision suggests microscopic remnants drive failure. We advocate for en-bloc resection with cortical decortication using a high-speed burr as the surgical gold standard. Conclusion: BPOP is locally aggressive. High recurrence after simple excision suggests microscopic remnants drive failure. We advocate for en-bloc resection with cortical decortication using a high-speed burr as the surgical gold standard.