Intramedullary osteoid osteoma in the humerus of a toddler-A case report and review of the literature

Abstract

Osteoid osteoma (OO) is a benign osteoblastic tumor characterized by nocturnal pain that responds well to non-steroidal anti-inflammatory drugs. This condition commonly affects adolescents and young adults, and patients between 5 and 24 years of age account for 85% of all OO cases; it occurs very rarely in patients under 5 years old. Tumors often occur in the cortical bone in the diaphysis and metaphysis of the appendicular skeleton and are more common in the lower extremities than upper extremities. Here, we present an extremely rare case of intramedullary OO that arose in the proximal metaphysis of the humerus in a 2-year-old boy, which mimicked subacute osteomyelitis on imaging studies. We also conducted a retrospective literature review and found that the intramedullary location was fairly common in very young patients (<6 years old) with OO.

Keywords: Bone tumor; Osteoid osteoma; Osteomyelitis; Pediatric.

Fig. 1

Radiograph, CT, and MRI of the right humerus at the patient's first visit (A: anteroposterior radiograph, B: coronal CT view, C: axial CT view, D: coronal view of T1-weighted MRI, E: coronal view of STIR MRI, F: axial view of T2-weighted MRI). The lucent area was located intramedullary, the nearby bone cortex was unilaterally thickened (white arrows in B, C), and a very fine calcification was observed inside the lucent area (black arrow in C). MRI on STIR showing exceedingly high intensity around the osteosclerotic zone which suggesting bone marrow edema (white arrows in E).

Fig. 2

Intraoperative photograph. The operation was completed after confirming that the lucent area could be completely excised by fluoroscopy.

Fig. 3

Photomicrograph of the excised tissue. Pathologically, woven bone surrounded by osteoblasts was seen. The cell size was little changed (H&E stain, ×200).

Fig. 4

Postoperative anteroposterior radiograph of right humerus taken immediately after surgery (A), 3 months after surgery (B), 6 months after surgery (C), 1 year after surgery (D), and 2 years after surgery (E). The bone lesion resolved over time.