Presentation
Arm pain since 1 year.
Patient Data
MRI of upper arm shows a well defined T2 and PDFS hyperintense lesion within the anterior cortex of upper humerus measuring ~10 x 6 mm with mild humeral marrow edema and mild adjacent anterior periosseous soft tissue edema. There is tiny T2 and T1 hypointense punctate focus in the center of lesion- representing ossified focus. No significant periosteal reaction noted.
These features are consistent with intracortical osteoid osteoma.
Corresponding CT sections confirm the lytic nature of cortical lesion in proximal humerus, representing nidus of the lesion. Punctate central ossified focus is noted, representing ossified osteoid. These features confirm the diagnosis of osteoid osteoma.
Case Discussion
Osteoid osteoma is a benign bone tumor with typical clinical features of night pain, relieved by salicylates. It is common in adolescent and young boys. Intracortical location is the most common type with intraarticular and subperiosteal being other types. Intraarticular lesions demonstrate no surrounding sclerosis.
MRI and CT are complementary in the diagnosis with MRI helping in identification of associated bone marrow edema.