September 24, 2023
Chromatin is a term used to describe the genetic material and associated proteins inside the nucleus of a cell. Pathologists can see chromatin when the tissue is stained with hematoxylin and eosin (H&E) and viewed under the microscope. This stain makes the chromatin look purple or blue.
Pathologists often use the microscopic look of the chromatin to help them understand a cell’s behavior. For example, ‘clumpy’, ‘coarse’, or ‘vesicular’ are words that are often used to describe chromatin in abnormal or even cancerous cells. In contrast, ‘smooth’ and ‘even’ are words that are used to describe normal or less worrisome cells. The appearance of chromatin is only one of many features pathologists use when making a diagnosis.
Pathologists use the word hyperchromatic (or hyperchromasia) to describe a cell that has very dark chromatin compared to the normal cells around it. A large round clump of chromatin is called a nucleolus or nucleoli if there are many large round clumps seen inside the nucleus of the cell.