What are thymic cancers?

Thymus gland cancers are cancers which start in the thymus gland located in the chest between the lungs. Cancers of the thymus gland are rare. The majority of such cancers are called thymomas. There is also a much rarer form of thymus gland cancer called thymic carcinoma. Thymomas and thymic carcinomas are cancers of the cells (called epithelial cells) that line the thymus gland.

You can find a good overview of these cancers on the following websites and we suggest you read the information that is provided. We have not repeated that information here.

www.macmillan.org.uk/information-and-support/thymus-cancer

www.cancerresearchuk.org/about-cancer/thymus-gland-cancer

Below, you will find some key, additional information based on our experiences as patients and our interactions with the medical profession.

How rare is rare?

You will find various reported incidence rates for thymomas and thymic carcinoma ranging from about 1 to 3 cases per million people. The majority of these cases will be thymomas.

Anecdotally in the UK at least, the incidence rate appears to be increasing however it is not clear whether this is due to an increase in occurrence and/or an increase in detection as a result of more people having X-rays and CT scans for other reasons.

What causes these cancers?

There is no known cause. Anyone can get a thymus gland cancer although they are most common in people aged between about 40 and 70. Thymomas are linked to certain other immune related diseases such as myasthenia gravis, rheumatoid arthritis, and systemic lupus erythematosus (SLE) and certain blood conditions such as pernicious anaemia, hypogammaglobulinemia, and red cell aplasia. The link, if there is one, between these conditions and thymic carcinoma is much less strong.

Are all thymomas and thymic carcinomas the same?

No, thymomas are a diverse group of tumours which are classified into different subtypes based on cell type and how different the tumour cells look from normal cells.

The different subtypes are A, AB, B1, B2 and B3.

It is not uncommon for a tumour to have a mixed subtype such as B2 and B3.

Thymic carcinomas are C type.

Some tumours are slow growing and they tend to be type A or AB, through to more aggressive tumours which tend to be type C.

The term ‘benign’ in relation to slow growing tumours should be avoided – they are rarely benign. The exact type of tumour is determined from a sample taken from the tumour either by a biopsy or following removal of the tumour by surgery. The subtype will help your medical team determine the best treatment options for you.

What is staging?

Staging relates to how far the tumour has spread and is different to the subtype. The stages (classified under the Masaoka-Koga staging system) are broadly

Stage 1 The cancer is inside the thymus gland and has not spread.

Stage 2a Microscopic spread.

Stage 2b Macroscopic (visible) progression from the thymus gland into surrounding fat but not into the lining of the heart or the lungs.

Stage 3 The cancer has spread into nearby organs such as the lungs or the lining of the heart (pericardium). It may have also grown into the blood vessels near the heart.

Stage 4a The cancer has spread to multiple sites in the lung and/or heart.

Stage 4b The cancer has spread to other distant organs, such as the liver, bones and sometimes the brain.

The above Masaoka-Koga classification is being replaced with a new system called the IASLC TNM classification which is essentially based on the ability to remove the tumour by surgery. Follow the link below for detailed information on the new system https://www.iaslc.org/Portals/0/staging_handbook_2016_hi-res_restricted_use_only_per_iaslc_permission.pdf?ver=2019-05-08-202520-383.

Thymomas rarely spread beyond the chest whereas thymic carcinomas are more likely to metastasise because they tend to be more aggressive.

The stage of the disease is determined through tests such as a CT-scan, a PET- scan and/or a MRI scan.

Both the staging and the subtype (A-C) are used by your medical team to determine the best treatment options for you.

What treatments are typically used?

The cornerstones of treatment are surgery, chemotherapy and radiotherapy.

 There are no ‘official’ NHS or NICE guidelines in the UK for the treatment of thymus gland cancers.  However, it is accepted that the gold standard treatment is to remove the tumour by surgery.

 If it is not possible to remove the tumour surgically (for example because of the proximity of the tumour to other major organs or blood vessels) then you might have chemotherapy in order to shrink the tumour such that surgery is possible.

 Radiotherapy is sometimes used post-surgery in order to ensure that any remaining cancer cells have been eliminated. If the tumour is inoperable you may have palliative chemotherapy and/or radiotherapy to control the growth of the tumour.

 In our community, we have patients who have had all of these treatments alone or in combination. For more information on treatment go to Treatments.

What is my prognosis?

There are various survival rates quoted in the scientific and medical literature. However, you should approach these with caution. Because of the rarity of these cancers, their diversity, the lack of detailed knowledge of both cause and likely progression together with the fact as individuals we are all different and will have respond to treatment differently, it is very difficult to predict prognosis.

Thymus gland cancers are not lung cancer and therefore even patients with a heavy disease burden can live full and active lives for many years, and many of us do.

 It is correct however that generally the prognosis for patients with thymic carcinoma is poorer than for patients with thymoma.

How experienced will my doctors be with these type of cancers?

Do not hesitate to ask your oncologist and your surgeon what experience they have in treating thymomas and thymic carcinomas. The likelihood is that your GP will not have had any experience of patients with these types of cancers and possibly your oncologist and your surgeon may have only limited experience. There are a number of oncologists and surgeons in the UK who are familiar with ThymicUK and who, we believe, are experienced with these types of cancers and have a particular interest in their treatment.  We would encourage patients to ask their local medical team to liaise as appropriate with oncologists/surgeons who may be more  experienced in these cancers. 

What questions should I be asking my medical team?

For all of us, knowing what questions to ask is a challenge, let alone understanding the answers! In our experience, asking others who are on the same journey as you what questions to ask or what things needs to be considered is very helpful. It is why we set up ThymicUK – so we could learn from and support each other. Please do join our UK Facebook community.

There is also an international Facebook community called the Thymoma Support Group which is also a valuable source of information and support.