Background: Osteochondroma is the most common benign bone tumor. However, there are infrequent studies karyotyping solitary osteochondromas. Methods: Retrospective review of the University of California, Los Angeles pathology database was performed for karyotype analyses (. N=522 specimens). Results: Two previously undescribed karyotypes were identified. First, was a karyotype showing paracentric inversion of chromosome 7. Second, was a karyotype showing monosomy 3, 6 and 13. Conclusions: Abnormal karyotypes may be more frequently encountered in osteochondroma than previously understood. However, the clinical significance of these abnormalities are yet unknown.