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

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