The stage of a tumour describes its size and whether it has spread. Knowing the stage helps doctors decide on the best treatment for you. Information about staging comes from your tests and scans and from the results of surgery.
These are the stages doctors use:
- Stage 1 – the cancer is only in the thymus and has not spread outside it.
- Stage 2 – the cancer has started to spread outside the thymus or into the fat tissue surrounding it.
- Stage 3 – the cancer has spread into nearby organs such as the lungs or lining of the heart (pericardium), and may have grown into blood vessels near the heart.
- Stage 4A – the cancer has spread widely into the lining of the lungs (pleura) and the lining of the heart (pericardium), and has spread to lymph nodes nearby.
- Stage 4B – the cancer has spread to other organs, such as the liver.
The doctor examines the cancer cells under a microscope to find out the type and grade of thymus cancer you have. This gives the doctor an idea of how the cancer may develop and how quickly it may grow. This can help your doctor to decide if you need more treatment after surgery
The type describes the type of cell the cancer has started growing from. It also tells your doctor if the cancer is a thymoma or a thymic tumour.
The grade of the cancer describes how different the cancer cells look from normal cells.
Doctors may group thymomas using the World Health Organisation (WHO) system. This uses letters from A to C, sometimes with numbers added, for the different types of thymoma. This is based on how the cells look under the microscope.
- Type A is the rarest type of thymoma. The cells in the tumour look quite normal.
- Type AB is also called a mixed thymoma. There are lymphocyte cells as well as thymus cells in the tumour.
- Type B1 has a lot of lymphocytes, along with normal looking thymus cells.
- Type B2 has a lot of lymphocytes and the thymus cells in the tumour look bigger than normal.
- Type B3 has few lymphocytes and the thymus cells look abnormal.
- Type C is also called thymic carcinoma. The thymus cells look very abnormal.
The most common type of thymoma is AB. This type can often be treated successfully. Most type B thymomas can also be treated successfully. Type C thymoma is often more advanced when it is diagnosed, so it can be harder to treat.