Secondary membranous nephropathy can be due to a multitude of causes, but there is an association to malignancy. Membranous nephropathy is classically associated with solid tumors and its presence can affect overall morbidity and mortality. Age and absence of anti-phospholipase A2 receptor appear to be the largest clues to paraneoplastic membranous nephropathy, and presence of thrombospondin 7A and NELL1 are highly linked to paraneoplastic membranous nephropathy. Most troublesome is the patient with no history of malignancy, patients on immunotherapy for their known malignancy, and patients post hematopoietic stem cell transplant as each present a unique set of diagnostic challenges. In the latter two scenarios, membranous nephropathy is a rare but described adverse reaction to immunotherapy, and membranous nephropathy is associated with graft versus host disease after stem cell transplant. In this review we discuss the epidemiology and pathophysiology linking membranous nephropathy to malignancy, challenges in diagnosis and management to include for patients receiving immunotherapy for their malignancy or in remission from their malignancy due to a stem cell transplant, and suggest a clinically relevant approach.