Clinical Case: Kidney Cancer Hides in 6-mm Breast Lesion

Medscape

20 hours ago

A 54-year-old woman with a history of renal cell carcinoma (RCC) developed a metastatic lesion in her breast 6 years after radical nephrectomy. The lesion, initially detected via routine imaging, was confirmed as RCC by histopathology and immunohistochemistry.
This case report by Aman Saswat Sahoo, a fourth-year Medicine & Surgery undergraduate at the University of Central Lancashire, School of Medicine and Dentistry, Preston, England, and colleagues, highlighted the need for meticulous diagnostic evaluation to distinguish between primary breast carcinoma and metastatic disease, particularly in patients with a history of RCC.
The Patient and Her History
The patient had a history of RCC that was initially treated with radical nephrectomy and no chemotherapy. She had undergone regular CT imaging since her surgery 3 years ago, and routine CT identified a 4-mm lesion in the lower outer quadrant of the right breast.
No other relevant preexisting medical conditions were reported. Her medical, family, travel, allergy, social, and drug histories were unremarkable.
Findings and Diagnosis
A clinical examination revealed no palpable abnormalities in both breasts. Mammography revealed a 6-mm nodule in the posterolateral region of the right breast, which was absent on a prior mammogram conducted 4 years earlier. Ultrasound imaging confirmed the presence of a solid nodule measuring approximately 5 mm in size. Ultrasound evaluation correlated these findings with a 5-mm benign-appearing nodule. A core biopsy was performed, and histopathologic evaluation showed an inflammatory lesion, characterised by cells with clear cytoplasm and macrophages. Considering the initial diagnosis, immunohistochemical staining provided crucial diagnostic clarity, with positive results for PAX8, CD10, and MNF116 markers, confirming metastatic RCC. Given the patient's history, these findings confirmed the presence of metastatic RCC in the right breast.
The patient was informed of the diagnosis of metastatic RCC in the right breast. Further assessment of distant sites and the potential for systemic therapy were discussed at this stage; however, it was later decided that no systemic interventions would be pursued. Although the lesion was considered minor in terms of surgical intervention, its identification is crucial as an indicator of metastatic disease.
Wide local excision was performed after tagging the lesion with a radiofrequency identification tag located 3 mm inferior to the original site; no axillary surgery was performed.
Postoperative histopathologic evaluation revealed a 5-mm well-circumscribed metastatic RCC. No vascular invasion, ductal carcinoma in situ, or lobular carcinoma in situ was identified.
Discussion
Although RCC is prominent in its ability to spread haematogenously, metastasis to the breast is extremely uncommon. The route for metastasis usually includes the migration of tumour cells from the kidneys through the inferior vena cava to the right ventricle of the heart. From here on, they enter the pulmonary circulation and eventually reach the breast.
Breast metastasis from RCC is exceedingly rare, with fewer than 60 cases documented in the literature. Although the risk for RCC recurrence is highest within the first 2 years following treatment, metastases to uncommon sites, such as the breast, have been reported even a decade after the initial diagnosis and surgical intervention.
'The limited information available in the literature regarding optimal treatment strategies and patient outcomes for RCC metastasis to the breast highlights the need for further studies to better understand this condition,' the authors wrote.