Sarcoid-like reaction to malignancy on whole-body integrated 18F-FDG PET/CT: prevalence and disease pattern
Introduction
Sarcoidosis is a systemic inflammatory disease of unknown cause that is characterized by the presence of non-caseating granulomas in affected tissues. The disease has multiple clinical manifestations, ranging from single organ involvement to multisystem disease.1 The link between sarcoidosis and malignancy is a controversial and confusing one, but there is evidence to suggest that such a relationship exists.2, 3 It is recognized that patients with established sarcoidosis have a higher incidence of lung cancer, and it has been shown that patients with sarcoidosis have a more than five-fold increased incidence of haematological malignancy.4 In a process that is often referred to as sarcoid-like reaction, non-caseating granulomas may also develop in patients with underlying cancer,5 and sarcoid-like reactions have been described in association with many different types of solid-organ malignancy.6, 7 With the increasing use of 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET) and PET/computed tomography (PET/CT) in cancer patients, it is being recognized that sarcoid-like reaction may result in FDG uptake that needs to be differentiated from tumour recurrence, as described in a few recent case reports.8, 9, 10, 11 This is the first study that describes the prevalence of this entity in cancer patients undergoing FDG PET/CT and analyses the patterns of FDG uptake seen in such cases, whilst emphasizing the importance of recognizing this pattern of abnormality in order to avoid a potential interpretive pitfall that may lead to inappropriate management.
Section snippets
Database search
A retrospective search of our institutional radiology information system (RIS) revealed that 2048 patients had attended FDG PET/CT examinations for staging or restaging of solid-organ malignancy between 1 September 2006 and 30 June 2008. Local ethics committee approval is not required in our institution for retrospective case series reviews. In cases of suspected sarcoid-like reaction identified from the original radiological reports, further information was obtained from the clinical and
Results
Twenty-four of 2048 (1.2%) cases were reported as having sarcoid-like reaction on FDG PET/CT from the original reports on the RIS. One patient was discovered to have known pulmonary sarcoidosis, clinical information that was unavailable to the initial reporter, and this case was excluded from further analysis. The diagnosis was confirmed in 13 of the remaining 23 cases (57%; Fig. 1). Histological confirmation was obtained in 10 of the 13, and clinical confirmation of the diagnosis by
Discussion
The development of non-caseating granulomas in patients with underlying malignancy is often referred to as sarcoid-like reaction, particularly when the patient is asymptomatic.5 It has been estimated that approximately 4–14% of all patients with cancer exhibit histopathological evidence of sarcoid-like reactions,3, 6 and this has been described in association with many tumour types, including haematological, testicular, pulmonary, gastric, colonic, breast, uterine, and sarcomatous neoplasms.3, 5
References (25)
Sarcoid reactions in malignant tumours
Cancer Treat Rev
(1986)- et al.
Sarcoidosis and malignancy
Clin Dermatol
(2007) - et al.
The incidence and significance of epithelioid and sarcoid-like cellular reaction in the stromata of malignant tumours. A morphological and experimental study
Eur J Cancer
(1970) - et al.
PET and PLAP in suspected testicular cancer relapse: beware sarcoidosis
Ann Oncol
(2001) - et al.
Results of 188 whole-body fluorodeoxyglucose positron emission scans in 137 patients with sarcoidosis
Chest
(2007) - et al.
Mediastinoscopy in patients with presumptive stage I sarcoidosis: a risk/benefit, cost/benefit analysis
Chest
(1998) - et al.
Sarcoidosis
N Engl J Med
(1997) - et al.
The incidence of malignant tumours in patients with respiratory sarcoidosis
Br J Cancer
(1974) The sarcoidosis–lymphoma syndrome
Br J Cancer
(1986)- et al.
Pulmonary and mediastinal “sarcoidosis” following surgical resection of cancer
Pathol Res Prac
(2004)