Open Access

CASE REPORT

Tumor-to-tumor metastasis: case report of a neuroendocrine tumor of the lung metastasizing to a benign oncocytoma of the kidney

Siddharth Marthi^1,*, Muhammad Mukarram¹, Fatemeh Ardeshir-Larijani², Lara Rabih Harik³, Shreyas Subhash Joshi^1,2

1 Department of Urology, Emory University, Atlanta, GA 30322, USA
2 Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA
3 Department of Pathology, Emory University, Atlanta, GA 30322, USA

* Corresponding Author: Siddharth Marthi. Email:

Canadian Journal of Urology 2025, 32(4), 349-353. https://doi.org/10.32604/cju.2025.063775

Received 23 January 2025; Accepted 23 April 2025; Issue published 29 August 2025

Abstract

Tumor-to-tumor metastasis (TTM) is a rare phenomenon in which a secondary tumor colonizes within a primary tumor of a different histogenesis. It is hypothesized that TTM is encouraged by conditions that promote increased cell growth and division in the primary tumor, such as hypervascularity and expression of oncogenic cytokines. However, the exact causes of TTM likely vary on a case-by-case basis and are dependent on the microenvironment of both the primary and secondary tumors. Herein, we present the first reported example of TTM in which a pulmonary neuroendocrine tumor (NET) metastasizes to a renal oncocytoma.

---

Keywords

---