Prevalence and clinical significance of focal incidental 18F-FDG uptake in different organs: an evidence-based summary

Abstract

Several meta-analyses and systematic reviews have reported data about the prevalence and the malignancy risk of focal incidental uptake detected by 18F-FDG PET (FIU). This review aims to summarize the published evidence-based data about the most common sites, prevalence and malignancy risk of FIU, to derive schematic estimates in this setting. A comprehensive computer literature search of meta-analyses or systematic reviews regarding FIU and published in PubMed/MEDLINE and/or Cochrane library database through June 2017 was carried out. Twelve articles were discussed in our summary and different organs were evaluated. The pooled prevalence of FIU ranged, respectively, from 1.6 to 3.6% for colon–rectum, from 1 to 2.46% for thyroid, being 0.4% for breast, 1.8% for prostate and 0.6% for parotid. Despite that, the pooled risk of malignancy considering histology as reference standard was quite high in all organs evaluated in the summary, except for parotid gland. In fact, it ranged from 61.5 to 76% for FIU in the colon–rectum (including both premalignant and malignant lesions), from 33.2 to 37% for FIU in the thyroid gland, and it was 60 and 62%, respectively, for breast and prostate FIU. For parotid FIU pathologically proven the pooled risk of malignancy was only 20.4%. Our summary showed that the most frequent sites of FIUs are colon and thyroid according to literature data. The risk of malignancy is quite high for FIU in colon-rectum, thyroid, breast and prostate especially when histologically analyzed. Beyond the localization, when FIU are detected further investigation is warranted.