The association between malignant tumors and the occurrence of glomerular disease has been well documented in previous studies. The most common types of malignant tumor include Hodgkin's lymphoma with minimal change glomerular nephritis, solid tumor with membranous nephropathy and renal cell carcinoma with immunoglobulin (Ig)A nephropathy. The present case study describes a case of a 31-year-old Chinese female patient who was hospitalized with chronic glomerulonephritis. The patient self-administered unknown traditional Chinese medicine; however, protein excretion/24-h remained increased compared with normal levels. After 34 months, a tumor was identified in the patient. Subsequently, the patient was administered breast-conserving surgery and sentinel lymph node biopsy, which validated the diagnosis of triple negative breast cancer at stage IA (T1cN0M0). The patient received chemotherapy and radiotherapy. Following the review of the relevant studies within the last 30 years, it was demonstrated that the present report was the second documented case of breast cancer associated with IgA nephropathy. Thus, the present study hypothesized that IgA nephropathy may be a tumor manifestation in breast cancer.