[Sarcoidosis and sarcoid reactions in cancer].

PURPOSE: Relationships between granulomatosis and cancers have been suspected for a long time. Nevertheless, few evidence has been reported until recently. Here, we present a literature review about the association of granulomatosis and neoplasia. CURRENT KNOWLEDGE AND KEY POINTS: Aside from granulomatosis due to infectious disease, granulomas can be observed in cancer patients, mainly in two situations. Patients may rarely present with typical sarcoidosis occurring before, during or after the diagnosis of cancer. Recent studies have documented such a relationship particularly with lymphomas, testicular and lung cancers, melanomas and hepatocarcinomas. Secondly granulomas may be found as a sarcoid reaction in the vicinity of the tumour itself or more frequently in regional lymph nodes. Sarcoid reaction, reported in Hodgkin's disease and gastric adenocarcinomas, may be associated with a better prognosis. Granulomatous reaction could play an important role in the host's defences against metastatic extension. Immunotherapy such as interferon has been reported to induce systemic sarcoidosis probably by reproducing some physiopathological mechanisms involved in sarcoidosis. FUTURE PROSPECTS AND PROJECTS: Clinicians need novel non invasive diagnostic methods to differentiate neoplasia from benign sarcoid reactions. The 18-fluorodeoxyglucose (18-FDG) PET-scan has failed in this indication but the adjunction of a [3-(18)F]-alpha-methyltyrosine ((18)F-FMT) PET-scan could be useful. Biopsies is still necessary in most of cases.