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Thymoma staging can be complicated, especially because there is no single, widely accepted staging system like there is for most other cancers. Many physicians rely on one of two models: the Masaoka system, which focuses on how far the cancer has spread, or the World Health Organization’s histological classification system, which focuses on the way the cells look underneath a microscope. When using the Masaoka thymoma staging system, physicians rely on imaging tests and tumor analyses to determine the extent of a cancerous growth. The stages in the Masaoka system are as follows:

  • Stage I – The tumor has not spread into the outer layer of the thymus.
  • Stage IIA – The tumor is starting to grow into the outer layer of the thymus or the nearby tissues and membranes.
  • Stage IIB – The tumor has already grown into the outer layer of the thymus or the nearby tissues and membranes.
  • Stage III – The tumor has started to grow into nearby tissues and organs.
  • Stage IVA – The tumor has grown extensively into nearby tissues and membranes.
  • Stage IVB – The tumor has spread to distant organs elsewhere in the body.

When using the World Health Organization’s histological thymoma staging system, a physician retrieves a small sample of a tumor, and then a pathologist examines it for specific cellular characteristics. The tumor is then labeled class A, class B1, class B2, class B3 or class C, depending on the characteristics of the cells and how they are arranged.  The process of staging a thymoma tumor is extremely important. The extent to which a cancer has spread and the type of cells that make up a tumor can directly impact the way the tumor responds to treatment, and should be considered when determining which treatments to recommend for a patient. At Moffitt Cancer Center, we perform all of our thymoma staging tests in our own on-site laboratories, allowing us to provide fast, accurate results for our patients. We then use this information to create individualized treatment plans that improve each patient’s prognosis and quality of life.

To learn more about thymoma staging, call 1-888-663-3488 or register to make an appointment with our Thoracic Oncology Program and our oncologists specializing in thymomas.