Sarcomatoid is a word used to describe cancer cells that look similar to the cells found in a type of cancer called sarcoma. However, sarcomatoid cells are not true sarcoma cells and the tumour is usually another type of cancer called a carcinoma.
Most cancers in adults develop from specialized cells called epithelial cells which line the surfaces of the body and form structures called glands. These types of cancers are called carcinomas. Most carcinomas are made up of round or rectangular shaped cells that like to stick together to form groups.
In contrast, a sarcoma is a rare type of cancer that typically develops from the cells that make up the connective tissues of the body. Sarcomas are usually made up of cells that are longer than they are wide (which pathologists call spindle cells) and that are less likely to stick together and form groups.
Sarcomatoid is not a diagnosis. It is a descriptive word that can be used for any tumour that starts to look like a sarcoma.