Abstract
BACKGROUND: Osteoid osteoma is an uncommon benign bone-forming tumor of the musculoskeletal system but it is the most common primary bone tumor of the carpal region. However, only seven cases of its pisiform involvement have been described. CASE: We present a 19 year-old male patient with osteoid osteoma of the pisiform which initially could not be detected in any diagnostic study for long standing wrist pain. The patient was treated with excision and curettage. In 1 year of follow-up, the patient was asymptomatic without recurrence. CONCLUSION: In cases with long standing ulnar wrist pain, one should consider osteoid osteoma of the pisiform in differential diagnosis. If an OO is suspected, thin slice CT scan in initial evaluation would be valuable in preventing the patient from misdiagnosis or delay in diagnosis.