Myositis and malignancy: is there a true association?

There may be an association between polymyositis/dermatomyositis and malignant disease. Cancer occurs in patients with polymyositis/dermatomyositis with a frequency estimated between 2.5% and 29% (relative risk 1.0 to 6.5). We present two such cases, associated with colorectal carcinoma and non-Hodgkin's lymphoma respectively, together with an overview of existing controlled studies in the area.