Tumor-to-tumor metastasis of breast carcinoma to clear cell renal cell carcinoma: a rare case with a review of the literature.

Authors

Nobuyuki Nakajima, Hiroshi Kajiwara, Kenta Okutsu, Toshiki Sakemura, Haruka Ikoma, Tatsuya Otaki, Soichiro Yuzuriha, Takato Uchida, Tatsuya Umemoto, Yoshiaki Kawamura, Yohei Masugi, Sunao Shoji

Published in

CEN case reports. Volume 15. Issue 4. Jul 28, 2026. Epub Jul 28, 2026.

Abstract

Tumor-to-tumor metastasis (TTM) is a rare clinicopathological phenomenon in which a malignant tumor metastasizes to another distinct neoplasm. Although renal cell carcinoma (RCC) is a frequent recipient tumor, metastasis from breast carcinoma to RCC is extremely rare. A 64-year-old woman with long-standing hormone receptor-positive breast carcinoma presented with a 23-mm enhancing right renal mass. Robot-assisted partial nephrectomy revealed clear cell RCC with intratumoral nests of metastatic breast carcinoma. Immunohistochemistry revealed a reciprocal staining profile: RCC cells were positive for PAX8 and CA9, whereas metastatic breast carcinoma cells expressed CK7 and GATA3 with weak ER positivity. Clear cell RCC may serve as a recipient tumor for breast carcinoma metastasis, emphasizing that TTM should be considered in the differential diagnosis of renal masses in patients with a history of breast carcinoma, even when imaging findings are consistent with conventional RCC.

PMID:
42518006
Bibliographic data and abstract were imported from PubMed on 28 Jul 2026.

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