Citation, DOI, disclosures and article data
Citation:
Banks K, Silverstone L, Knipe H, Flip-flop fungus sign - FDG PET-CT. Reference article, Radiopaedia.org (Accessed on 23 Apr 2024) https://doi.org/10.53347/rID-164872
Disclosures:
At the time the article was created Kevin Banks had the following disclosures:
- Not applicable , Not applicable (ongoing)
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The flip-flop fungus sign suggests benign pulmonary disease on FDG-PET 1-4.
Lung cancer nodules demonstrate increasing FDG-avidity as the tumor grows. Lymph node spread occurs later and is therefore at an earlier stage of development and usually exhibits lower FDG-avidity 4.
Acutely, FDG-avidity in fungal lung nodules exceeds avidity in draining lymph nodes and can mimic cancer. As inflammation subsides, the lung nodule avidity diminishes but lymph node avidity can persist for months. The flip-flop fungus sign refers to this situation of nodal activity exceeding lung nodule avidity, the reverse of the usual findings in lung cancer 5-7.
In areas of endemic histoplasmosis or coccidioidomycosis, serology makes the diagnosis and directs treatment. Fungal disease will regress on treatment.
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1. Nagelschneider A, Broski S, Holland W et al. The Flip-Flop Fungus Sign: An FDG PET/CT Sign of Benignity. Am J Nucl Med Mol Imaging. 2017;7(5):212-7. PMC5698614 - Pubmed
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2. Kraskovsky V, MacKenzie B, Arshad A, Mador M. Flip Flop Fungus Sign: An FDG PET Sign of Benign Pulmonary Nodules. BMJ Case Rep. 2020;13(11):e236231. doi:10.1136/bcr-2020-236231 - Pubmed
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3. Ruegg G, Zimmerli S, Trachsel M et al. Pulmonary Histoplasmosis Mimicking Metastatic Lung Cancer: A Case Report. Diagnostics (Basel). 2021;11(2):328. doi:10.3390/diagnostics11020328 - Pubmed
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4. Sebro R, Aparici C, Hernandez-Pampaloni M. FDG PET/CT Evaluation of Pathologically Proven Pulmonary Lesions in an Area of High Endemic Granulomatous Disease. Ann Nucl Med. 2013;27(4):400-5. doi:10.1007/s12149-013-0695-7
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5. Wong T, Tan T, George U, Kow K, Liam C. Application of F-FDG PET-CT in the Management of Pulmonary Nodule and Mass - a Pictorial Review. Med J Malaysia. 2019;74(3):250-6. - Pubmed
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6. Varghese C, Azadeh N, Sakata K. The Flip-Flop Fungus Sign in Pulmonary Coccidioidomycosis. Chest. 2018;154(4):187A. doi:10.1016/j.chest.2018.08.163
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7. Kunin J, Blasco L, Hamid A, Fuss C, Sauer D, Walker C. Thoracic Endemic Fungi in the United States: Importance of Patient Location. Radiographics. 2021;41(2):380-98. doi:10.1148/rg.2021200071 - Pubmed
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