Radiation Oncology/Thymoma/Staging
|
Thymoma Staging
- There is no universally accepted system; no AJCC staging existed before the 8th edition, which will go into effect January 1st, 2018 in the United States
- Historically, a classification system used both histological features and clinical behavior
- Masaoka staging is the clinically used staging system, although it may not be predictive for thymic carcinoma
- GETT staging is the surgical staging system, and may have better correlation with outcome
- A meta-analysis from UCLA suggests that evaluation of transcapsular extension (Stage I vs. Stage IIa) is of no clinical value, as they have same DFS and OS outcomes
Historical Classification
- Benign Thymoma (histologically and behaviorally benign)
- Malignant Thymoma (invasive)
- Type I - histologically benign, but behaving aggressively with local invasion
- Type II ("thymic carcinoma") - histologically malignant, aggresive behavior
Masaoka TNM Staging (1999) - PMID 10047676
| Stage | Description |
|---|---|
| T1 | Macroscopically completely encapsulated AND microscopically no invasion |
| T2 | Invasion into or through the capsule |
| T2a | Microscopic invasion into capsule |
| T2b | Macroscopic adhesion, or invasion into surrounding fatty tissue, or mediastinal pleura |
| T3 | Invasion into neighboring organs |
| T3a | No invasion of great vessels |
| T3b | Invasion of great vessels |
| T4 | Pleural or pericardial dissemination |
| N | Lymph node status |
| N1 | Anterior mediastinal LNs |
| N2 | Intrathoracic LNs except anterior mediastinal LNs |
| N3 | Supraclavicular LNs |
| M0 | Metastatic status |
| M1 | Hematogenous metastasis or extrathoracic LNs except supraclavicular LNs |
Original Masaoka Staging (1991) - PMID 1913546
- Stage I - Macroscopically and microscopically completely encapsulated
- Stage II - Macroscopic invasion into surrounding fatty tissues or mediastinal pleura or microscopic invasion into the capsule
- Stage III - Macroscopic invasion into adjacent organs or intrathoracic metastases
- Stage IVA - Pleural or pericardial implants/dissemination
- Stage IVB - Nodal or hematogenous metastases
GETT Staging
- Stage IA - Encapsulated, completely resected
- Stage IB - Macroscopically completely resected but suspicion of mediastinal adhesions or potential capsular invasion at surgery
- Stage II - Invasive tumor, completely resected
- Stage IIIA - Invasive tumor, subtotal resection
- Stage IIIB - Invasive tumor, biopsy alone
- Stage IVa - Supraclav or pleural met
- Stage IVb - Distant metastases