Most of the genetic material inside a cell is found in a small structure called the nucleus. Pathologists can see the nucleus by adding a stain called H&E to the tissue. Pathologists use the word hyperchromasia to describe a nucleus that looks darker than normal when examined under the microscope. Another word for hyperchromasia is hyperchromatic.
A nucleus can show hyperchromasia for different reasons. Non-cancerous cells often show hyperchromasia when they are injured. Pathologists sometimes describe these cells as reactive. Hyperchromasia can also be seen in pre-cancerous conditions such as dysplasia and in many different types of cancers. In these situations, hyperchromasia is used to support the diagnosis.