Thymus cancer

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What is thymus cancer?

Thymus cancer is a malignant tumour that starts in cells of the thymus. Malignant means that it can spread, or metastasize, to other parts of the body.

The thymus is part of the endocrine system, which makes and releases hormones that help cells function. It is also part of the lymphatic system, which makes and stores cells that fight infection and diseases by keeping your immune system working normally. The thymus is a gland just behind the breastbone and between the lungs. The thymus is most active when you’re a child or teenager.

The thymus has 2 irregularly shaped sides, or lobes. Each lobe has 3 layers. The outer covering is called the capsule. Inside the capsule is the cortex. The inner layer is called the medulla. The cortex and medulla are made up of a mixture of epithelial cells and lymphocytes. Epithelial cells form a layer that covers the blood vessels and connective tissue in the thymus. Lymphocytes are a type of white blood cell.

Cells in the thymus sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous, or benign, tumours such as thymic cysts and thymolipoma.

In some cases, changes to thymus cells can cause cancer. Most often, thymus cancer starts in epithelial cells in the cortex or medulla. Thymoma is the most common type of thymus cancer. Thymic carcinoma is another type of thymus cancer. It is rare but aggressive.

Other rare types of thymus cancer can also develop. These include non-Hodgkin or Hodgkin lymphoma, neuroendocrine tumours and germ cell tumours.

Diagram of location of the thymus

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