Thymus gland cancers are rare malignancies that develop in the thymus gland, which sits in the mediastinumthe space between the lungs that holds many important structures, including the heart, trachea and oesophagus. The thymus gland is a part of the lymphatic systema network of tissues and organs that help our bodies fight infection and disease, which is a network of tissues and organs that help our bodies fight infectiona condition where harmful pathogens, such as bacteria, viruses or parasites, have entered the body and disease.
The thymus gland is responsible for the production and maturation of T lymphocytes, a type of white bloodthe red bodily fluid that transports oxygen and other nutrients around the body cell that regulates the body’s immune response and helps protect the body from pathogensany substance or organism that has the potential to cause disease (e.g. bacteria, viruses, fungi, parasites etc.). Once developed, the T lymphocytes travel to the lymph nodessmall bean-shaped structures that filters harmful substances from lymph fluid in the body, which filter out damaged and potentially harmful cellsthe basic structural and functional unit of all living things.
This type of cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs is slightly more common in men, and is most often found in people in their 70’s. However, anyone can develop this disease.
Types of Thymus Gland Cancer
There are two primary types of thymus gland cancer, which are both classified as carcinomas (cancers arising from epithelial cells that line organs). They are differentiated by how the cancer cells look under the microscope, and by their growth patterns.
Thymomas
Thymomas are the most common thymus gland cancer, and originate from epithelial cells in the thymus gland. Thymoma cells look very similar to healthy thymoma cells, tend to be slow-growing, and rarely metastasise. Thymomas are often categorised using a letter system.
Type A
Type A thymomas are the rarest subtype of the disease. They are classified by spindle-shaped or oval shaped cells, which look very similar to healthy thymus gland epithelial cells. Type A thymomas are slow growing, have a low recurrenceto occur or happen again rate, and often have the best prognosisto predict how a disease/condition may progress and what the outcome might be.
Type AB
Type AB thymomas, or mixed thymomas, have areas with type A and type B thymomas. These tumours are one of the most common subtypes of the disease, often have a good prognosis.
Type B
Type B thymomas are the most common type of thymoma. These tumours often develop quicker than other subtypes, and can be aggressive in some cases. Type B thymomas are often assigned a number to describe cellular appearance:
- B1: thymoma is lymphocyte-rich with epithelial cells looking similar to healthy cells. B1 thymomas often have the best prognosis.
- B2: thymoma is still lymphocyte-rich, but epithelial cells appear larger and have abnormal nuclei. B2 thymomas are the most common subtype, and can have a good prognosis when caught early.
- B3: thymoma has less lymphocytes, and has epithelial cells that look very abnormal. B3 thymomas may not have as good of a prognosis as other type B thymomas.
Thymic Carcinomas
Thymic carcinomas are a rare form of thymus gland cancer that also originates from epithelial cells in the thymus gland. This type of cancer is more aggressive than thymomas, and tend to grow and metastasise at a faster rate. Because of how rare they are, thymic carcinomas are often diagnosed at an advancedat a late stage, far along stage of disease, and may not have as good of a prognosis as other thymus gland cancers.
Rare Forms of Thymus Gland Cancer
These types of cancers are considered very rare:
- Thymic lymphomas – thymus gland cancer that develops only from white blood cells instead of epithelial cells.
- Thymic neuroendocrine tumours (thymic NETs).
Treatment
If a thymus gland cancer is detected, it will be staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets and how the cancer cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumoura tissue mass that forms from groups of unhealthy cells) indicates the size and depth of the tumour.
- N (nodea small lump or mass of tissue in your body) indicates whether the cancer has spread to nearby lymph nodes.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissuea group of cells that work together to perform a function.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localisedaffecting only one area of body cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for thymus gland cancer may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence, potentially including:
- Thymectomycomplete or partial removal of the thymus gland.
- Lymphadenectomysurgical removal of lymph node(s).
- Segmentectomy (lung)removal of a portion of a lobe of the lung (only for advanced cancers that have metastasised to the lung).
- Wedge resectiona surgical procedure where a small, triangular portion of tissue or organ is removed of the lung (only for advanced cancers that have metastasised to the lung).
- Lobectomya surgical procedure where a lobe of an organ (e.g. the lung) is removed (only for advanced cancers that have metastasised to the lung).
- Pericardiectomyremoval of the pericardial layer of tissue covering the heart (only in advanced cancers that have metastasised to the heart).
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Hormone therapymedication that alters the levels of certain hormones in the body, such as oestrogen and progesterone.
- Targeted therapymedication that targets specific molecular features of cancer cells.
- Immunotherapya treatment that uses a person's immune system to fight cancer.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
Because of how rare thymus gland cancers are, there has been limited research into the riskthe possibility that something bad will happen factors of this disease.
Symptoms
Symptoms of a thymus gland tumour may include:
- Dyspneadifficulty breathing, shortness of breath.
- Persistent cough.
- Chest pain.
- Hoarseness of the voice.
- Difficulty swallowing.
- Superior vena cava syndrome (caused by tumour pressing on the superior vena cava vessela tube that carries bodily fluid, such as blood or lymph fluid, around the body), which carries its own set of symptoms:
- Swelling of the face, neck, and/or upper chest.
- A bluish complexion from the upper chest up.
- Swelling of visible veins from the upper chest up.
- Headaches.
- Dizziness.
- Unexplained weight loss and/or loss of appetite.
Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have a thymus gland cancer, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- PET (positron emission tomography) scana type of medical imaging that uses radioactive tracers to create detailed images of the body.
- Chest x-raya type of medical imaging that uses x-ray beams to create detailed images of the body .
- Blood teststesting done to measure the levels of certain substances in the blood.
- Pulmonary function testa test that examines how well your lungs are working.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
Thymus Gland Cancer Support Groups
A cancer diagnosis can be difficult and overwhelming for you and your family, and may affect your emotional and mental health. Support services can help dealing with your diagnosis, connect with others with a thymus gland cancer, provide access to professional support, and potentially improve emotional wellbeing and mental health. For more information on support services available to you, please refer to the Rare Cancers Australia Support Groups page.
