Background: Tumors metastatic to the breast are a rare occurrence. The correct identification is essential as there are divergent management implications. Fine needle aspiration cytology (FNAC) is an effective method of diagnosis when coupled with the judicious use of immunocytochemistry.
Case: A 50-year-old Indian woman presented with a palpable right breast lump that was clinically suspicious for malignancy. There were no contralateral breast masses or palpable axillary lymphadenopathy. There was a history of nephrectomy carried out several years earlier for renal cell carcinoma (RCC). FNAC of the right breast lump yielded malignant epithelioid and occasionally spindled cells within an inflamed background, while immunocytochemistry showed positive reactivity of tumor cellsfor CD10, with negative staining for CK7. The cytologic diagnosis favored a tumor of renal origin. The patient underwent wide central excision of the right breast lump, whereby the diagnosis of metastatic RCC with sarcomatoid features was confirmed. On follow-up, she developed metastases to multiple organ sites and died.
Conclusion: A high index of suspicion is required in the diagnosis of disease metastatic to the breast. FNAC is a reliable diagnostic tool in the distinction of metastasis from primary malignancy of the breast.