Pseudotumor deltoideus: a previously undescribed anatomic variant at the deltoid insertion site.

A spectrum of eccentric bone irregularities were observed in the humeral deltoid tuberosity region of five patients. Patients were referred for associated pain or for the incidental radiographic findings. The lesions are characterized radiographically by a relative lucency at or adjacent to the deltoid tuberosity, variably increased uptake on the bone scan, and mild cortical irregularity or adjacent eccentric marrow abnormality on MRI and CT. The term pseudotumor deltoideus is coined for these previously undescribed anatomic variants. Imaging studies and extended clinical follow-up in these patients support an inactive or indolent process that may be managed conservatively. The potential etiology and role of these cortical irregularities as tumor simulators is emphasized.