The epidemiology and biology of pulmonary metastases

Abstract

Our goal in this chapter is to explore the complex processes of metastasis and why there is a predisposition for this to occur in the lung. In addition, we aim to describe the incidence of pulmonary metastases in various contexts and based on the origin of the primary tumor. There are unique characteristics of the pulmonary system that make metastases more likely to occur in the lung than anywhere else in the body. Some of these characteristics include receiving the entire cardiac output every minute, having the densest capillary bed in the body, and being the first reservoir of most lymphatic drainage entering the venous system. There are multiple postulated routes of metastasis to the pulmonary system including hematogenous and lymphatic routes with early or late dissemination. The vascularization of pulmonary metastases is variable and complex, often recruiting supply from bronchial and pulmonary origin. There are also many biochemical factors in the tumor microenvironment that play a key role in the development of lung metastases including vascular endothelial growth factor (VEGF), interleukin-8 (IL-8), very late antigen 4 (VLA-4) and intercellular adhesion molecule 1 (ICAM-1). Studies vary widely in reported rates of pulmonary metastases due to differences in clinical study design, however, it is commonly accepted that up to half of autopsies performed on patients who died of malignancy have pulmonary metastases. In a surgical series describing the incidence of primary cancer types with resected pulmonary metastases the most common sites were thyroid, colon, breast, genitourinary tract, skin, liver, breast, and adrenal glands.

Inhaled Gold Nano‐Star Carriers for Targeted Delivery of Triple Suicide Gene Therapy and Therapeutic MicroRNAs to Lung Metastases: Development and Validation in a Small Animal Model

“…The lungs are the most common sites for metastases from extrathoracic cancers because of the unique anatomical and biological characteristics of the pulmonary system. [ 1 ] Unfortunately, the most common malignant tumors in the lungs are metastases, [ 2 ] and up to half of the patients who die of malignant cancers have pulmonary metastases at autopsy. [ 1 ] In particular, the incidence of lung metastases is highest among patients with triple‐negative breast cancer (TNBC), accounting for 10–15% of all breast cancer.…”

Anti-CK7/CK20 Immunohistochemistry Did Not Associate with the Metastatic Site in TTF-1-Negative Lung Cancer

“…When a patient presents with a lung tumor, clinically the probability that it is a metastasis of a cancer of another origin is high [ 6 ]. Primary lung tumors are less common than lung metastases in clinical practice [ 6 ].…”

“…When a patient presents with a lung tumor, clinically the probability that it is a metastasis of a cancer of another origin is high [ 6 ]. Primary lung tumors are less common than lung metastases in clinical practice [ 6 ]. Anti-CK7 and CK20 antibodies are important in suggesting the site of origin of the most common cancers.…”

The Lymphatic System in Breast Cancer: Anatomical and Molecular Approaches

“…These characteristics permit intravasation and the spread of circulating cancer cells (CTC) [42]. As an example, the pulmonary metastases of breast cancer find in the hematogenous mechanism their most common route of spreading [43]. Moreover, in breast cancer, CTC quantification has been used as a prognostic and predictive biomarker to guide treatment in the metastatic disease [44].…”