Metastatic clear cell renal cell carcinoma presenting as breast lump: A rare case report

Renal cell carcinoma is as an aggressive tumor associated with metastasis in about one‐third of the cases, but it rarely metastasizes to breast, which further is a rare site of metastasis from extramammary solid tumors. Here, we report the case of a 60‐year‐old female who presented with breast metastasis from renal cell carcinoma. The mammogram showed a well‐defined hyperdense mass of 2.5 × 2.7 cm with microlobulated margins. The mass was hypervascular on ultrasound. Further, contrast enhanced computed tomography (CECT) abdomen revealed a 6.3 × 6.0 × 6.2 cm mass arising from the middle and the lower pole of right kidney. Fine‐needle aspiration cytology (FNAC) of the right breast lump, along with cellblock preparation from the aspirated material and immunohistochemistry (IHC) on the cellblock was performed. The tumor was positive for pan‐cytokeratin, vimentin, and CD10, while the markers for primary breast carcinoma were negative. On the basis of morphology and IHC, the final diagnosis of the breast mass was metastatic clear cell renal cell carcinoma. This case highlights the importance of ruling out possibility of metastasis in cases of breast mass. The correct diagnosis of these cases is crucial since the mastectomy is not required. Here, we discuss the radiological and morphological features on cytology and cellblock of this rare case of breast metastasis from renal cell carcinoma.