Synchronous occurrence of primary breast cancer and renal cell carcinoma: A case report and literature review

Introduction and importance: Multiple Primary Malignant Neoplasms (MPMNs) are rare and refer to the occurrence of two or more distinct primary cancers with unrelated histopathological features in one patient. MPMNs can be classified as synchronous when tumors appear simultaneously or within six months of each other, and as metachronous when identified six months or more after the initial cancer diagnosis. While breast cancer often cooccurs with other primary cancers such as colorectal, endometrial, and ovarian cancers, the simultaneous presence of invasive lobular breast carcinoma and clear cell renal cancer is rare. Case presentation: Here, we present the case of a 59-year-old postmenopausal woman who initially presented with breast carcinoma. Further investigation revealed a mass in the left kidney. The patient underwent a radical mastectomy and axillary dissection, followed by a left nephrectomy. After 8 months follow up, the patient is doing well and disease-free. Clinical discussion: Based on our case and literature review, the co-occurrence of breast carcinoma with renal cell carcinoma (RCC) is uncommon. Most reported cases involve metastatic tumors or metachronous breast malignancy with RCC. The etiology of synchronous malignancy is complex, and treatment options usually include a combination of surgery and/or adjuvant therapy. Conclusion: This case report contributes valuable insights to the limited literature on synchronous breast cancer with renal cell carcinoma. The rarity of this simultaneous occurrence underscores the importance of considering such cases. Documenting these cases is crucial for increasing awareness and reducing the resulting morbidity and mortality.