Positron emission tomography in the evaluation of pulmonary nodules among patients living in a coccidioidal endemic region

Background: Within a coccidioidal endemic region, pulmonary nodules due to coccidioidomycosis are common. Uptake of ¹⁸fluorodeoxyglucose ( ¹⁸FDG) by positron emission tomography with computed axial tomography (PET/CT) has been used to assess whether pulmonary nodules are malignant but inflammatory lesions can be positive. The purpose of this study was to compare by PET/CT the ¹⁸FDG uptake in pulmonary nodules likely due to coccidioidomycosis to that of nodules shown to be malignant among patients living in a coccidioidal endemic region. Methods: We retrospectively reviewed patients who underwent a PET/CT at the Southern Arizona Veterans Affairs Health Care System between January 2008 and March 2012 who were subsequently found on biopsy to have pulmonary nodules that were coccidioidal or granulomatous or were due to malignancy. Results: Among 245 diagnostic biopsies where the subject had a previous PET/CT, 15 (6.1 %) were either coccidioidal (n = 12) or granulomatous without an identified organism (n = 3). The median maximum standard unit of uptake (SUV_max) on PET/CT of coccidioidal or granulomatous lesions was 2.0 compared to 9.8 for malignant lesions (P < 0.001). The maximum diameter of the coccidioidal or granulomatous nodules was 2.1 cm compared to 3.0 cm for the malignant lesions (P = 0.009). On multivariable analysis, an elevated SUV_max was the only distinguishing feature between the malignant and the granulomatous lesions (OR 1.28, 95 % CI 1.05-1.55; P = 0.013). Conclusions: Coccidioidal pulmonary nodules take up significantly less ¹⁸FDG than those due to malignancies, but there is considerable overlap between granulomatous and malignant lesions at lower SUV_max.