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Cancer Imaging

Open Access

Prevalence of malignancy in patients with fever of unknown origin (FUO) demonstrated in 18F-FDG PET-CT – prospective multi-centre study

Cancer Imaging201414(Suppl 1):P4

Published: 9 October 2014


18F-FDG PET-CT plays an important role in the management of fever of unknown origin. FUO is defined as “body core temperature <38.3°C on several occasions lasting for <3 weeks but no cause found despite routine clinical investigations for <1 week in hospital”. Malignancy is an important cause of FUO, and the aim of this study is to demonstrate prevalence of malignancy as a cause of FUO demonstrated in PET-CT.


A total of 231 patients with FUO were prospectively studied using PET-CT after negative conventional investigations. Final diagnosis was based on biopsy, microbiological tests and imaging follow-up.


The cause of FUO was identified only in 129/231 (56%) patients, of which 27 (12%) were due to malignancy and 102 were due to benign causes.

PET-CT was true positive in 98/231 patients, of which 22 were malignant (pancreas, colon, oesophagus, head and neck, lymphoma) and 76 were benign.

False positive in 18/231 patients, due to increased FDG-uptake in reactive nodes.

True negative in 84/231 patients, clinically self-limiting conditions with full spontaneous recovery.

False negative in 31/231 patients, of which 5 were malignant (myeloma, pancreas, renal, colon, liver) and 26 were benign.

PET-CT identified malignancy in 22/27 (81%). PET-CT misses poorly-FDG-avid malignancy or lesions embedded within normal physiological uptake.


In this study 12% (27/231) of FUO are caused by malignancy. PET-CT demonstrated the site of malignancy in 81% (22/27). Although PET-CT plays an important role in the management of FUO, some malignancy may be missed (19%) so further investigations are still required if spontaneous recovery is not achieved.

Authors’ Affiliations

Paul Strickland Scanner Centre, Mount Vernon Hospital, London, UK


© Sonoda et al; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.