Keratinization is a word pathologists use to describe cells producing large amounts of a protein called keratin. Cells that produce keratin are stronger than other cells which makes them good at forming a barrier between the outside world and in the inside of the body.
Squamous cells are a type of cell that normally produce large amounts of keratin. The keratin makes the cell look pink when examined under a microscope.
Keratinization can be a normal process. For example, keratinization allows our skin to be waterproof. Keratinization can also be abnormal. For example, too much keratin causes us to develop callouses from wearing ill-fitting shoes or repeated use of equipment with our hands.
Some types of cancer, for example squamous cell carcinoma, can also show keratinization.