Cyclin D1


November 28, 2023

Cyclin D1 is part of a family of proteins called cyclins. All cyclins are cell cycle regulators, meaning they help determine when a cell can divide (to create two new cells). Cyclins can be further broken down into multiple families and subtypes. These all work in slightly different ways, but they all push cells to divide. This protein is often expressed in cells that divide under physiologic (normal) states.

What types of normal cells express cyclin D1?

  • Basal cells in the epidermis of the skin.
  • Epithelial cells on the surface of the cervix.
  • Specialized immune cells within germinal centers.

What does cyclin D1 do?

Cyclin D1 triggers a process that ultimately ends in cell division or the creation of two new cells. It does this by directly activating cyclin-dependent kinase 4 (CDK4), which then activates other cyclins and cyclin-dependent kinase complexes. Together, these signals cause cells to divide.

How do pathologists test for cyclin D1?

The most common way to test for cyclin D1 is by immunohistochemistry (IHC). Pathologists often perform this test to see if the cells in a tumor are producing higher-than-normal levels of this protein. This is important when trying to distinguish between two tumours that look very similar when examined on routine hematoxylin and eosin (H&E) stained slides. For example, small lymphocytic lymphoma and mantle cell lymphoma are both made up of small B cells. However, mantle cell lymphoma expresses large amounts of cyclin D1 while small lymphocytic lymphoma does not.  In this situation, immunohistochemistry can be a helpful tool in distinguishing between these two lymphomas, which are managed differently.

What types of tumors express cyclin D1?

Many different types of tumours express high levels of cyclin D1. As a result, testing for this protein is not performed because this information is not required to make a diagnosis. However, there are specific situations where the expression of cyclin D1 plays an important role in making the diagnosis or helps determine prognosis.

Examples of tumours that express high levels of cyclin D1 include:

Other types of tumors that can express high levels of cyclin D1 and where testing may aid in the diagnosis include:

Related articles on MyPathologyReport

Immunohistochemistry (IHC)
Mantle cell lymphoma

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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