Thymus cancer

Structure of the thymus

The thymus is divided into 2 main parts – a right lobe and a left lobe. Each lobe is divided into smaller sections called lobules that give the thymus its bumpy appearance. Each lobule is made up of a centre part (called the medulla) and an outer layer (called the cortex). A thin covering (capsule) surrounds and protects the thymus.

The thymus is mainly made up of epithelial cells, immature and mature lymphocytes and fat tissue.

The thymus changes in size as you get older. It is large in newborns and toddlers. It is biggest during puberty then slowly begins to shrink as adulthood approaches.

The thymus is most active during childhood and youth. By late adulthood, most of the thymus is made up of fat tissue.

What the thymus does

The thymus makes T cells (T lymphocytes) that travel throughout the body to help fight infection, disease and foreign substances. The thymus also makes hormones to help T cells develop and keep the immune system working properly.

Lymphocytes travel from the bone marrow to the thymus, where they mature into T cells. Once T cells mature, they are able to leave the thymus and enter the blood so they can help the immune system. T cells also travel to lymph nodes and the spleen where they continue to mature.

What is thymus cancer?

Thymus cancer starts in the cells of the thymus. Learn about symptoms, diagnosis, treatment and risks in our guide to thymus cancer.

The thymus

The thymus is a gland in the upper part of the chest, just behind the breastbone (sternum) and between the lungs. The thymus is part of the endocrine system and the lymphatic system.

Cancerous tumours of the thymus

Malignant tumours of the thymus are cancerous growths that have the potential to spread (metastasize) to other parts of the body. Most thymus tumours are found in the anterior (front) mediastinum, near the left lung and in front of or to the side of the pericardium.

Classification of thymoma and thymic carcinoma

Thymoma and thymic carcinoma can be divided into groups based on what the cancer cells look like under a microscope. Along with the stage, this classification helps your healthcare team plan your treatment and predict future outcomes (your prognosis).

Risks for thymus cancer

There are no known risks for thymus cancer.

Symptoms of thymus cancer

A sign is something that can be observed and recognized by a doctor or healthcare professional (for example, a rash). A symptom is something that only the person experiencing it can feel and know (for example, pain or tiredness). The signs and symptoms of thymoma or thymic carcinoma can also be caused by other health conditions.

Diagnosis of thymus cancer

Diagnosis is the process of finding the cause of a health problem. Diagnosing thymus cancer may begin with a visit to your family doctor. Your doctor will ask you about any symptoms you have and may do a physical exam. But most often thymus cancer is found by chance when you have tests for other reasons.

Stages of thymus cancer

Staging is a way of describing or classifying a cancer based on the extent of cancer in the body. Two staging systems are used to classify thymoma and thymic carcinoma – the modified Masaoka system and the TNM system.

If thymus cancer spreads

Cancer cells have the potential to spread from tumours in the thymus to other parts of the body where they can grow into new tumours. This process is called metastasis. The tumours are also called metastasis (singular) or metastases (plural). Metastases are also called secondary tumours.

Prognosis and survival for thymus cancer

If you have thymoma or thymic carcinoma, you may have questions about prognosis and survival. Prognosis and survival depend on many factors. Only a doctor familiar with your medical history, type of cancer, stage, characteristics of the cancer, treatments chosen and response to treatment can put all of this information together with survival statistics to arrive at a prognosis.

Treatments for thymus cancer

Treatment for thymoma and thymic carcinoma is given by cancer specialists (oncologists). Some specialize in surgery, some in radiation therapy and others in chemotherapy (drugs). These doctors work with the person with cancer to decide on a treatment plan.

Supportive care for thymus cancer

Supportive care helps people meet the physical, practical, emotional and spiritual challenges of thymoma or thymic carcinoma. It is an important part of cancer care. There are many programs and services available to help meet the needs and improve the quality of life of people living with cancer and their loved ones, especially after treatment has ended.

Thymus gland cancer statistics

Cancer statistics tell us how many people in Canada are diagnosed with and die from other endocrine cancers in a certain time frame.

Your trusted source for accurate cancer information

With just $5 from readers like you, we can continue to provide the highest quality cancer information for over 100 types of cancer.

We’re here to ensure easy access to accurate cancer information for you and the millions of people who visit this website every year. But we can’t do it alone.

If everyone reading this gave just $5, we could achieve our goal this month to fund reliable cancer information, compassionate support services and the most promising research. Please give today because every contribution counts. Thank you.

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

We do our best to make sure that the information we provide is accurate and reliable but cannot guarantee that it is error-free or complete.

The Canadian Cancer Society is not responsible for the quality of the information or services provided by other organizations and mentioned on cancer.ca, nor do we endorse any service, product, treatment or therapy.


1-888-939-3333 | cancer.ca | © 2025 Canadian Cancer Society