Differentiation
An excerpt from an ESUN article
Pathologists and oncologists often describe a particular tumor’s potential for aggressive behavior in terms of "differentiation." Differentiation of any cell is a description that means that a given cell type has certain characteristics that make it unique, or "different" from other cell types. For instance, a fat cell is different from a cartilage cell, because these two cell types have many characteristics that differ from each other. Many types of connective tissue cells come from common precursor cells, but as they get signals to express certain proteins and develop certain characteristics, they fall into a unique cell type category. Sarcoma cells are cells that resemble or are derived from these cell types, but have undergone a transformation into a malignancy. That is, they have developed the capacity to metastasize.
Differentiation is a description of how closely the tumor resembles its cell of origin on the histologic (microscope) evaluation and gives a guide to the treating physicians of how aggressive a behavior to expect from a given patient’s tumor. A well-differentiated tumor very closely resembles the cell line that it is derived from, whereas a poorly differentiated tumor has very few characteristics of its cell line of origin. This is an important distinction, as well-differentiated tumors have a lower potential for aggressive or aberrant behavior than poorly differentiated tumors, which can behave very aggressively. Additionally, the term “dedifferentiated” is usually used to describe a tumor that no longer has any detectable relationship to its origin cell line, and can only be diagnosed as being related to that cell line based on the background it is found in. For instance, a patient with a well-differentiated liposarcoma has a tumor that closely resembles adipose, or fat, tissue and has little propensity, if any, to metastasize. However, within that patient’s well differentiated liposarcoma if there were to be found a defined area that no longer has any resemblance to fatty tissue, but has the more characteristic appearance of an aggressive malignant spindle cell neoplasm, this area would then likely be considered a dedifferentiated area of the well-differentiated liposarcoma, or an area of dedifferentiated liposarcoma. It is important to note that these dedifferentiated tumors, since they behave differently from their related tumor type, may need to be treated quite differently than that related tumor type.
Michael J. Weaver, MD and John A. Abraham, MD
V4N2 ESUN Copyright © 2007 Liddy Shriver Sarcoma Initiative.