Acetabular Aneurysmal Bone Cyst

Background: aneurysmal bone cysts (abcs) are benign destructive tumors. their diagnosis is sometimes challenging, and their treatment in unusual sites, especially in the pediatric age group is difficult, too. this study aims to support the paraclinical measures along proper consultation to approach the pelvic abc. methods: we present a 9-year-old female who suffered from pain in the left hip 3 months before the referral. a pelvic mass was diagnosed and unfortunately misdiagnosed with an ovarian mass. it was led to a wrong operation with a wrong approach by a general surgeon and result in intraoperative bleeding and delay in diagnosis and treatment. the final diagnosis was massive abc in the supraacetabular area with extension to the ilium and pubic. conclusion: pelvis is one of the most challenging sites for the diagnosis and treatment of bone tumors. large abc tumors in the hip are unusual and may be presented by nonspecific signs and symptoms. therefore complete clinical and radiological evaluations should be done before any attempt to surgically remove the pelvic mass. prognosis is excellent if the pelvic mass remove wisely by an experienced hip surgeon.