# Tumor-to-Tumor Metastasis of Lung Cancer to Kidney Cancer: A Review of the Literature and Our Experience

## TL;DR

This paper reviews the rare phenomenon of lung cancer metastasizing into kidney cancer and discusses its implications for cancer management.

## Contribution

The paper presents a case study and literature review on tumor-to-tumor metastasis from lung to kidney cancer.

## Key findings

- Tumor-to-tumor metastasis is rare but documented in multiple primary cancer patients.
- Lung carcinomas are common metastatic donors to renal cell carcinoma.
- No specific management guidelines exist for tumor-to-tumor metastasis.

## Abstract

Tumor-to-tumor metastasis (TTM) is a rare phenomenon documented in patients with multiple primary cancers. This condition is defined as a metastasis between two true primary tumors. The most frequently reported recipient tumor is renal cell carcinoma (RCC), and the lung carcinomas are the most common metastatic tumor donors. Therefore, this paper attempts to address the current gap in knowledge about this rare phenomenon. The first part of this review outlines the recently proposed models and mechanisms involved in the TTM process. The second part then summarizes and analyzes previous case reports in the literature. We also present our experience with the case of lung cancer that metastasized into RCC. Given the sporadic incidence of TTM, no specific management guidelines exist. Therefore, considering TTM in patients with multiple primary tumors is important as it could potentially modify the oncological management offered.