That foreign bodies, not only bacteria, viruses and parasites, can be the cause of various pathologies is a well-known fact.
Silicosis, asbestosis, inflammatory reactions to the debris from worn out hip prostheses are only a few among many possible examples.What has been unclear, or utterly ignored, so far, is that foreign bodies below a certain size can enter, mainly through ingestion or respiration, animal organisms and travel rather freely through their tissues. They can either negotiate the gastro-intestinal wall or the pulmonary alveoli and be carried by the blood or the lymph, or settle in a tissue they run into on their migratory way.
According to their size, those foreign bodies can be divided into nano-particles, if their order of magnitude is between 10-9 and 10-7 m, and micro-particles if they range between 10-6 and 10-5 m.
If those bodies are chemically inert and not biodegradable, they induce a reaction through which the organism defends itself against that form of invasion, and that reaction, whatever it is, can either pass unnoticed or be of clinical relevance.Nanopathology is the branch of learning that deals with the reactions the organism opposes to the presence of those small-sized particles.

Barium-Sulfhate debris in liver cancer.