Mammary Carcinoma Metastasizing to Renal Cell Carcinoma: A Case Report

Abstract Introduction/Objective The simultaneous occurrence of multiple primary cancers is rare, and even rarer is the phenomenon of one cancer metastasizing to another. Here, we present a case of mammary carcinoma and renal cell carcinoma diagnosed concurrently yet presenting as a cancer-to-cancer metastasis. Methods/Case Report A 79-year-old woman, with a 2-week duration of apnea and cough, was found to have right pleural effusion and underwent thoracocentesis. Cytological examination of the fluid revealed malignant cells suggestive of adenocarcinoma. CT abdomen and chest revealed a 1.6 cm right breast nodule, 4.4 cm right axillary mass and right renal lesions measuring 3.0 and 1.6 cm. Core biopsy of the renal lesion showed two populations of cells. One population exhibited moderate cytoplasm and enlarged nuclei displaying anisonucleosis and hyperchromasia arranged singly as well as in sheets and clusters. These cells stained positive for GATA 3, ER, mammaglobin and CK7. Intermixed, were the second population of cells with clear cytoplasm and low nuclear grade forming sheets and replacing renal tissue. These cells were positive for CA9, CD10 and PAX 8 but negative for P40. Based on these findings a diagnosis of low-grade renal carcinoma of clear cell type with a metastatic carcinoma of mammary origin was established. Results (if a Case Study enter NA) NA Conclusion Renal cell carcinoma and breast carcinoma are known to increase the occurrence of each other. When breast and renal lesions are identified concurrently, the possibility of breast metastasis should be strongly considered. However, the concurrent appearance of renal cell carcinoma harboring metastatic breast cancer is extremely rare.This contributes valuable insights into the complex interplay between different cancer types. Understanding these rare phenomena can aid in refining diagnostic approaches and treatment strategies.