Joint pain is one of the major symptoms in early leukemia. We report on a 16-year-old girl who presented with groin pain and an osteolytic bone lesion. Acute lymphoblastic leukemia was diagnosed, but the laboratory workup and radiologic imaging revealed atypical results. Particularly in early precursor B-cell acute lymphoblastic leukemia, comparable initial symptoms and signs have been reported in adolescents; therefore, we recommend performing a bone marrow aspiration early on in cases of suspected osteolytic bone lesions.