Diagnosis, Staging & Masaoka-Koga Classification

Diagnosis

Approximately 30% of patients with thymoma or thymic carcinoma have no symptoms when it is diagnosed. These are typically detected when doctors are looking for other things, during routine chest x-rays, for example.

If there are symptoms, they include:

  • Persistent Coughing
  • Chest pain
  • Upper airway congestion
  • Muscle weakness
  • Fatigue
  • Shortness of breath
  • Arm or facial swelling
  • Difficulty swallowing
  • Anemia (low red blood cell count)
  • Increased risk of infection

Staging

It is important to know the stage of a cancer or tumor, which also helps in selecting the treatment.


The system most often used in staging thymomas is called the Masaoka system, after the doctor who, in 1981, first proposed it. This system separates thymomas into four stages.

The system has been modified over the years, so the following staging for thymomas and thymic carcinomas is generally:

  • Stage I: Grossly and microscopically encapsulated. Also called a noninvasive thymoma. That is, it has not spread beyond the thymus.
  • Stage II: The thymoma invades beyond the capsule (outer boundary of the thymus) and into the nearby fatty tissue or to the pleura (outer covering of the lung). Sometimes divided into:
    • Stage IIa: Microscopic transcapsular invasion
    • Stage IIb: Macroscopic capsular invasion
  • Stage III: Macroscopic invasion of neighboring organs. The thymoma extends into the neighboring tissues or organs of the lower neck or upper chest area, including the pericardium (covering of the heart), the lungs, or the main blood vessels leading into or exiting from the heart.
  • Stage IVA: Pleural or pericardial dissemination. The thymoma has spread widely throughout the pleura and/or pericardium.
  • Stage IVB: Hematogenous or lymphatic dissemination. The thymoma has spread to distant organs.

Application of this staging system to a series of 85 surgically treated patients confirmed its value in determining prognosis, with 5-year survival rates of 96% for stage I disease, 86% for stage II disease, 69% for stage III disease, and 50% for stage IV disease. In a large retrospective study involving 273 cases of thymoma, 20-year survival rates (as defined by freedom from tumor death) according to the Masaoka staging system were reported to be 89% for stage I disease, 91% for stage II disease, 49% for stage III disease, and 0% for stage IV disease.

Stage Treatment

  1. Complete surgical excision
  2. Complete surgical excision and postoperative radiotherapy to decrease the incidence of local recurrence
  3. Complete surgical excision and postoperative radiotherapy to decrease the incidence of local recurrence
  4. Surgical debulking, radiotherapy, and chemotherapy

Because thymic carcinomas are so rare, no universal staging system has been developed for them. Some doctors use the Masaoka system for thymic carcinoma as well as for thymomas.

The most common chemotherapy drugs in the treatment of thymoma are doxorubicin (Adriamycin, Rubex), cisplatin (Platinol), cyclophosphamide (Cytoxan, Neosar), etoposide (VePesid, Etopophos, Toposar), and ifosfamide (Ifex, Holoxan). The common combinations used for the treatment of thymoma include cyclophosphamide, doxorubicin, and cisplatin or etoposide and cisplatin. These chemotherapy combinations are sometimes used to shrink the tumor before surgery if the thymoma is more advanced. Chemotherapy may also be used for people who have stage IVB advanced thymoma or recurrent thymoma that is not resectable. The most common protocols are PAC and ADOC