Breast cancer with nephrotic syndrome: report of two cases

We report two cases of women found to have breast cancers within a few months of being diagnosed with nephrotic syndrome. Case 1 was a 53-year-old Japanese woman in whom breast cancer was diagnosed 14 months after the onset of nephrotic syndrome. The histological diagnosis was invasive ductal carcinoma with no lymph node metastasis. We performed a modified radical mastectomy, after which the proteinuria and hypoproteinemia resolved almost completely, and the patient has been disease-free for 5 years since. Case 2 was a 61-year-old Japanese woman in whom breast cancer was diagnosed 2 months after the onset of membranous nephropathy. We performed a modified radical mastectomy and the histological diagnosis was invasive ductal carcinoma with marked lymphatic vessel permeation and involvement of five axillary lymph nodes. Proteinuria and hypoproteinemia did not resolve postoperatively and there is a high possibility of remnant or recurrent cancer. To our knowledge, there are only four other reported cases of paraneoplastic membranous nephropathy complicating breast cancer. However, we speculate that the postoperative resolution of nephrotic syndrome might be a measure of cancer control.