An association between the glomerular disease membranous nephropathy (MN) and malignancy has long been appreciated, but evidence supporting this relationship remains limited, speculative, and, at times, controversial. Reports that the two disease processes often evolve in parallel, as well as the occasional findings of tumor antigens or tumor-reactive antibodies within glomerular immune deposits, are all supportive of an association. However, the diagnosis of both MN and malignancy in the same individual also may be coincidental, especially in an older demographic group in which both diseases tend to occur. This article briefly reviews the proposed pathogenetic mechanisms of idiopathic and secondary forms of MN, as well as the arguments for and against the contention that malignancy-associated MN is itself a distinct clinical entity. In addition, the recent identification of the M-type phospholipase A₂ receptor as a major glomerular antigen in idiopathic MN has the potential to offer fresh tools that might help resolve some of the controversy, and ultimately aid in the decision of how aggressively to screen for malignancy in an individual diagnosed with MN.
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