18F-FDG PET/CT Imaging Features of IgG4-Related Pulmonary Inflammatory Pseudotumor at Initial Diagnosis and During Early Treatment Monitoring.

We present a proven case of pulmonary inflammatory pseudotumor that illustrates the (18)F-FDG PET/CT imaging features of this "great mimicker of malignancy" both at initial diagnosis and during early monitoring of corticosteroid therapy, which is advocated as the first-line treatment. Although the patient showed some symptomatic response to corticosteroid therapy, as well as a modest reduction in SUVmax, complete surgical resection was eventually needed in view of the relative nonresponse. (18)F-FDG avidity in untreated cases of pulmonary inflammatory pseudotumor has been quite characteristic and may potentially be used to evaluate early response of this IgG4-related disease to nonsurgical treatment and to detect residual disease or recurrence after therapeutic intervention.