Purpose of review: To examine recent data about the association between rheumatic disorders and cancer. This article focuses on paraneoplastic rheumatic disorders, which usually precede by a short period of time the diagnosis of malignancy, and on malignant transformation, which occurs late in the course of rheumatic disorders. Evidence of causality between malignancies and rheumatic disorders was reviewed based on statistical indicators (standardized incidence ratios and odds ratios) and by applying Bradford Hill's criteria of causality.
Recent findings: Firm epidemiological evidence was found attesting that dermatomyositis and polymyostis may present as paraneoplastic syndromes. Several other musculoskeletal disorders may be present akin to paraneoplastic syndrome, based on clinicians' impressions, but with scarce epidemiological evidence supporting a causal determinism. In contrast, robust evidence has accumulated on the role of longstanding rheumatoid arthritis, Sjögren's syndrome and systemic sclerosis as premalignant conditions. Evidence that systemic lupus erythematosus may evolve into lymphoma is equivocal.
Summary: The link between malignancies and rheumatic disorders may impact on clinical practice. First, paraneoplastic rheumatic syndromes can provide the clinician with hints for earlier diagnosis of occult cancer. Second, the risk of malignant transformation during the course of rheumatic disorders may motivate the search for strategies aimed at prevention.