1. The Current Staging Systems of Thymoma
2010 대한흉부외과학회 춘계학회
The Current Staging Systems of Thymoma
성균관대학교 흉부외과
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2. Thymoma the most common neoplasm of the anterior mediastinum
“rather enigmatic tumor”
controversy on histologic classification & staging
- low incidence
- wide range of histological appearance
- unique biologic behavior

3. Case : M/40, symptoms of myasthenia gravis
Bx. (mediastinotomy)
; Thymoma, WHO type A
Mass excision
: Thymoma, WHO type B3

4. Definition & terms : confusion
Thymoma
Thymic epithelial tumor
Thymic carcinoma
Malignant thymoma
Invasive thymoma
Atypical thymoma

5. Thymoma : benign or malignant ?
Thymic carcinoma : 흉선암, malignant
Thymoma : 흉선종, benign?
invasiveness of thymoma
no clear histologic distinction
Lymphoma, melanoma : malignant tumor

6. Histologic classification of thymic epithelial neoplasm (1)
Bernatz (1961)
Kirchner &
Muller-Hermelink (1989)
WHO (1999)
Lymphocyte-predominant
Mixed lymphoepithelial
Epithelial- predominant
Medullary
Mixed
Predominantly cortical
Cortical
A (medullary)
AB (mixed)
B1 (organoid, predominantly cortical)
B2 (cortical)
Epithelial-predominant
with cytologic atypia
Well-differentiated thymic carcinoma
B3 (epithelial)
High-grade carcinoma
C*(thymic carcinoma)
Now excluded in the new WHO classification (2004) and
placed in a separate group of malignant epithelial tumors.

7. Histologic classification of thymic epithelial neoplasm (2)
WHO (1999)
Suster
&Moran
(1999)
Suster & Moran(2006)
A (medullary)
AB (mixed)
B1 (organoid, predominantly cortical)
B2 (cortical)
Thymoma
Well-differentiated thymic ca.
(thymoma, low-grade or grade I)
B3 (epithelial)
Atypical thymoma
Moderately differentiated thymic ca.
(thymoma, intermediate grade or grade II)
C* (thymic carcinoma)
Thymic carcinoma
Poorly differentiated thymic ca.
(thymoma, high grade or grade III)
Now excluded in the new WHO classification (2004) and
placed in a separate group of malignant epithelial tumors.

8. WHO classification & clinical staging
Okumura (2001)
Type
Number of cases
Stage I II
III
IVa
IVb
Invasive tumors
(%) A 8 7 1
12.5 AB 44 27 15
38.6 B1 25 5 4
40.0 B2 36 11 10 12 2
69.4 B3 6
80.0 C 14
100.0
Unclassified 3
0.0
Totals
140 65 33 32
53.6

9. Staging of thymoma Staging of thymoma continues to be a
controversial issue.

10. Thymoma has no official staging system!

11. Staging schemes of thymoma
Stage
Bergh(1978)
Wilkins(1979)
Masaoka(1981) I
Intact capsule or growth within the capsule “
Macroscopically completely encapsulated and microscopically no capsular invasion II
Pericapsular growth into the mediastinal fat tissue
+ or adjacent pleura or pericardium
Macroscopic invasion into surrounding fatty tissue or mediastinal pleura
II-1 (IIa)
Microscopic invasion into capsule
II-2 (IIb)
III
Invasive growth into the
surrounding
organs and/or
intrathoracic
metastases
Macroscopic invasion into a neighboring organ (e.g., pericardium, great vessels, or lung)
Pleural or pericardial dissemination
IVa
Hematogenous or lymphogenous metastases
IVb

13. Overall survival rates of thymoma
Authors
Patients number
Complete resection rate (%)
5-year, 10-year survival
Stage I
Stage II
Stage III
Stage IVa
Kondo (2003)
924 92
100%, 100%
98%, 98%
89%, 78%
71%, 47%
Nakahara(1988)
141 80
92%, 84%
88%, 77%
47%, 47%
Pan(1994)
112
94%, 87%
85%, 69%
63%, 58%
41%, 22%

14. Survival curve of thymoma : Korea
n=108
n=195
연세대. Chest (2005)
성균관대. Br J Ca (2007)

15. Criticisms on Masaoka staging
Bedini (2005), Kondo(2005)
not well suited for the staging of thymic carcinomas
not provide an appreciable prognostic separation between stages I and II
Definition of stage II is unclear. Tumors invading the mediastinal pleura are at higher risk of recurrence than the other stage II tumors.
no description of residual tumor
Stage III thymoma is highly heterogenous in terms of involved organs.
The TNM system classification of thymic epithelial tumors has not been established.

16. Modification of Masaoka staging
Koga et al. (1994)
simplified into two groups
non-invasive for stages I and II
invasive for stages III and IV

17. Modification of Masaoka staging
Stage
Trastek(1989)
Kornstein(1995) I
Completely encapsulated No capsular invasion
Intact capsule II
Growth into capsule
Invasion into surrounding fat; adjacent mediastinal pleura
Growth within capsule (a) Microscopic invasion through capsule into
adjacent mediastinal tissue (b) Gross and microscopic invasion through capsule
into surrounding fat or adjacent pleura or
pericardium
III
Invasion into neighboring structures (pericardium, lung, great vessels)
Invasion into surrounding structures (great vessels,
lung) IV
(a) Pleural or pericardial metastasis (b) Lymphatic or hematogenous metastasis
(a) Pleural or pericardial dissemination (b) Lymphogenous or hematogenous metastasis

18. Staging (French Classification) - Groupe d'Etudes des Tumeurs Thymique, GETT 1982
Stage I
Encapsulated, noninvasive. Total excision.
Localized invasion to mediastinal structures. Total excision.
Stage II
Invasive growth into the surrounding organs. Total excision.
Stage III
Invasive growth into the surrounding organs. Incomplete excision.
Invasive growth into the surrounding organs. Biopsy of tumor.
Stage IV
Largely invading tumor cells with (supra)clavicular nodes or pleural or pulmonary grafts (metastases) .
Hematogenous metastasis (1 or more).

19. Verley and Hollmann classification (1985)
Stage
Characteristics I
Encapsulated, noninvasive tumor; total excision Ia
without adhesion to the environment Ib
with fibrous adhesion to mediastinal structures II
Localized invasiveness, e.g., pericapsular growth into the mediastinal fat tissue or adjacent pleura or pericardium
IIa
complete excision
IIb
incomplete excision, with local remnants of tumor
III
Largely invading tumor
IIIa
invasive growth into the surrounding organs and/or intrathoracic tumorous grafts (pleura, pericardium)
IIIb
lymphogenous or hematogenous metastasis

20. Prognostic categories for thymoma
proposed by Suster and Moran (2003)
Favorable
Group I
Encapsulated or minimally invasive thymoma
Completely excised
Equivalent to WHO histologic types A, AB, B1, B2
Group II
Equivalent to WHO histologic type B3
Group III
Widely invasive thymoma or thymoma with implants
All histologic types
Unfavorable
Group IV
Incompletely excised
Group V
Widely invasive thymoma with or without intrathoracic metastases
Unresectable/biopsy only
Group VI
Widely invasive thymoma with distant metastases

22. New staging systems for testing
Asamura (2004)
Stage
Description I
Tumors without any invasion into other structures/structures/structures/organs regardless of capsular involvement II
Scheme 1: tumors smaller than 10 cm in diameter and involving only one neighboring structure/organ
Scheme 2: tumors of all combinations of diameter and number of involved strctures/organs other than those in stage III
III
Scheme 1: tumors of all combinations of diameter and number of involved structures/organs other than those in stage II
Scheme 2: tumors 10 cm or more in diameter and involving two or more neighboring structures/organs IV
Tumors with pleural or pericardial dissemination (IVa) or lymphatic/vascular metastasis (IVb)
Masaoka staging
Scheme 1
Scheme 2

23. Tumor size : thymoma prognosis
Bloomberg(1995) : 11cm
Wright(2005) : 8cm
Nakagawa(2003) : 10cm

24. Survival of patients with stage III disease
Results Of Surgical Treatment Of Thymomas With Special Reference To The Involved Organs
Okumura (1999)
Survival of patients with stage III disease

25. Stage III Thymic Epithelial Neoplasms are Not Homogeneous with Regard to Clinical, Pathological, and Prognostic Features
성균관대. J Thorac Oncol (2009)

26. LN metatasis : 2.4%
hematogenous metastasis : 5.3%

27. Proposed TNM schemes for thymoma and thymic carcinoma
Yamakawa, Masaoka (1991) T T1
Macroscopically completely encapsulated and without microscopic capsular invasion T2
Macroscopic adhesion or invasion into surrounding fatty tissue or pleura or microscopic invasion of the capsule T3
Invasion into neighboring organs such as great vessels, pericardium, lung T4
Pleural or pericardial dissemination N N0
No lymph node metastasis N1
Metastasis to anterior mediastinal lymph nodes N2
Metastasis to intrathoracic lymph nodes (other than anterior mediastinal nodes) N3
Metastasis to extrathoracic lymph nodes M M0
No distant metastases M1
Hematogenous metastases
Stage T N M I T1 N0 M0 II T2
III T3
IVA T4
IVB
Any
N1-3 M1

28. Pattern of LN metastasis
Kondo (2003)
Thymoma
Thymic carcinoma

30. The INT (Istituto Nazionale Tumori) TNM-Based Staging System
No capsular invasion T2
Microscopic invasion into the capsule, or extracapsular involvement limited to the surrounding fatty tissue or normal thymus T3
Direct invasion into the mediastinal pleura and/or anterior pericardium T4
Direct invasion into neighboring organs, such as sternum, great vessels, and lungs; implants to the mediastinal pleura or pericardium, only if anterior to phrenic nerve N0
No lymph node metastasis N1
Metastasis to anterior mediastinal lymph nodes N2
Metastasis to intrathoracic lymph nodes other than anterior mediastinal nodes N3
Metastasis to prescalene or supraclavicular nodes M0
No hematogenous metastasis
M1a
Implants to the pericardium or mediastinal pleura beyond the sites defined in the T4 category
M1b
Hematogenous metastasis to other sites, or involvement of lymph nodal stations other than those described in the N categories
Stage grouping
Classification of residual disease i
Locally restricted disease
T1-2 N0 M0 ii
Locally advanced disease
T3-4
anyT
N1-2
iii
Systemic disease N3
anyN M1 R0
No residual tumor R1
Microscopic residual tumor
R2a
Local macroscopic residual tumor after reductive resection (> 80% of the tumor)
R2b
Other features of residual tumor

31. Progression-free survival
Masaoka staging
INT(Istituto Nazionale Tumori) staging

32. Thymoma vs. Thymic ca.
thymoma
normal thymus
thymic carcinoma

33. Thymic carcinomas Low-grade malignancy High-grade
Well-differentiated squamous cell carcinoma
Basaloid carcinoma
Mucoepidermoid carcinoma
Large-cell carcinoma with Castleman's disease
High-grade
Lymphoepithelioma-like carcinoma
Poorly differentiated squamous cell
Adenosquamous carcinoma
Clear cell carcinoma
Papillary adenocarcinoma
Mucinous adenocarcinoma
Sarcomatoid carcinoma
Poorly differentiated carcinoma
Hepatoid thymic carcinoma
Anaplastic/undifferentiated carcinoma

37. 1. stage III thymoma
2. thymic carcinoma

39. Key points of thymic tumor staging
Frank C. Detterbeck, Alden M. Parsons
Pearson’s thoracic and esophageal surgery, 3rd Edition.
chapter 131. Thymic tumors: A review of current diagnosis, classification and treatment
By multivariate analysis, the most important prognostic factors in patients with thymomas are stage and completeness of resection.
All stages and all histologic subtypes of thymoma have the potential to spread to distant sites.

40. 감사합니다.