Fine-needle aspiration cytology of renal-cell adenocarcinoma metastatic tothe breast: A report of three cases

Metastases to the breast from extramammary primary malignancies, including renal adenocarcinoma, are rare. Fine-needle aspiration biopsy (FNA) is a us eful, noninvasive, and rapid procedure to evaluate these mammary lesions. T his study describes the cytomorphology of 3 cases of renal-cell adenocarcin oma metastatic to the breast. All patients had a prior history of renal-cel l adenocarcinoma treated with radical nephrectomy, and they presented with a solitary mammary mass. The cytologic findings showed irregular clusters a nd dispersed single cells with eccentric nuclei and abundant, vacuolated cy toplasm in a hemorrhagic background. The nuclei were round to oval, with fi ne granular chromatin and a single, prominent nucleolus. All aspirates were interpreted initially and correctly as consistent with metastatic renal-ce ll adenocarcinoma. In summary, a cytologic diagnosis of renal-cell adenocar cinoma metastatic to the breast can be made by correlating clinical and cyt ologic findings. The distinction between metastatic extramammary malignanci es to the breast and primary mammary carcinoma is critical to avoid unneces sary surgery and to ensure appropriate chemotherapy or radiation therapy. D iagn. Cytopathol. 21:324-327, 1999. (C) 1999 Wiley-Liss, Inc.