Incidental detection of elastofibroma dorsi on PET-CT: Initial findings and changes in tumor size and standardized uptake value on serial scans

Objective We describe changes in elastofibroma dorsi (EFD) as observed in serial fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET-computed tomography (CT) imaging studies. Materials and methods ¹⁸F-FDG PET-CT studies carried out between January 2006 and January 2015 at a single institution were reviewed by an experienced radiologist and nuclear medicine specialist. When available, previous or subsequent imaging studies were reviewed to evaluate changes in EFD. Results Of 28 500 PET-CT studies carried out, EFD was identified in 68 from 20 patients (mean age 67.1±10.2 years; 14 women). Five patients had unilateral lesions and 15 patients had bilateral lesions. Eighteen patients had oncologic diseases. The mean size of EFD at first presentation was 13.95±5.90 mm and the mean homogeneous low-grade ¹⁸F-FDG uptake was maximum standardized uptake value (SUV_max) 2.24±0.95. One or more additional CT scans were performed in 17 patients; the mean interval between the first and last scans was 57.4±39.2 months. EFD was unchanged in size in 7/17 (41%) and showed slow growth in 10/17, reaching a mean size of 19 mm. The mean monthly growth rate was 0.1±0.10 mm. PET imaging in 11 patients showed a mean first SUV_max of 2.08±1.17 and a mean last SUV_max of 2.74±1.05 after a mean of 47.5±31.5 months (P=0.63). Conclusion Serial PET-CT studies may show a stable or slowly enlarging mass on a CT scan without changes in ¹⁸F-FDG uptake on PET imaging. Familiarity with CT appearances and ¹⁸F-FDG uptake of EFD are important for correct interpretation of ¹⁸F-FDG PET-CT studies.