What is chromatin?

Chromatin is the genetic material and the proteins that surround the genetic material inside a cell. Most of the chromatin is found in an area of the cell called the nucleus.

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.

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