Case report: Renal clear cell carcinoma presenting with metastatic nodules in the male breast: a case and literature review.

Metastasis of renal cell carcinoma (RCC) most frequently occurs in the lungs, bones, liver, and brain. Breast metastasis from RCC is exceedingly rare, particularly in male patients presenting with a breast mass as the initial manifestation. We report a 54-year-old man who presented with a breast nodule that, upon excision, was pathologically confirmed as metastatic Clear cell RCC. Abdominal computed tomography (CT) revealed a primary lesion in the left kidney. One month and nine months after laparoscopic partial nephrectomy, recurrent metastatic lesions were detected in the breast. After two subsequent excisions of the breast metastases, the patient was treated with lenvatinib in combination with tislelizumab. However, treatment was discontinued due to intractable diarrhoea. Three months after treatment cessation, follow-up CT imaging revealed widespread systemic metastases. The patient is currently maintained on sunitinib monotherapy. The total duration of follow-up was 30 months. This case, together with a review of earlier reported cases of RCC with breast metastasis, reveals the interesting observation that female patients with RCC appear to be more susceptible to "delayed" breast metastasis compared with male patients. Our analysis underscores the need for thorough evaluation of breast nodules in patients with an RCC history, even absent classic signs like nipple retraction or discharge. These findings may contribute to the future development of effective management guidelines for breast metastases from RCC and help clinicians better recognize this clinical entity.