The term “tumor lineage” typically refers to the ancestral or developmental lineage of cells that give rise to a tumor. Tumors are abnormal masses of tissue that result from uncontrolled cell growth, and they can arise from different types of cells in the body. The lineage of a tumor describes the specific cell type or types from which the tumor originated.

For example, a tumor lineage might be epithelial if it arises from cells that make up the epithelium (the tissue that covers the surfaces of organs and structures in the body). Tumors can also have a mesenchymal lineage if they originate from cells of connective tissue or muscle.

Understanding the tumor lineage is important in cancer research and treatment because different types of tumors may respond differently to various therapies. It can also help in identifying the specific genetic and molecular characteristics of the tumor, which can inform the development of targeted therapies.

It's worth noting that the term “lineage” in this context is related to the cellular origin of the tumor and is not the same as the genetic lineage, which refers to the sequence of genetic events leading to the development of a tumor.