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#redirect [[Thymus#Thymoma]]
'''Thymoma''' is a common tumour of the [[thymus]].
 
==General==
*Strong association with autoimmune disease, esp. myasthenia gravis.
 
===Classification===
The ''WHO'' published a widely used system - WHO classification:<ref>{{Ref Sternberg4|1264}}</ref>
====Type A====
*AKA ''Spindle cell'' or ''medullary''.
*Arise from ''medullary epithelial cells''.
*Good prognosis.
 
IHC:
*Usu. keratin+.
====Type AB====
*Like Type A... but with foci of lymphocytes.
====Type B1====
*Near normal, expanded cortex.
 
Lesion consists of:
*>2/3 lymphocytes, <1/3 cortical epithelial cells.
====Type B2====
*Neoplastic cells with some resemblance to cortical epithelial cells.
**Epithelioid cells with distinct nucleoli.
**May be perivascular.
*Large population of lymphocytes.
 
Lesion consists of:
*<2/3 but >1/3 lymphocytes, >1/3 but <2/3 cortical epithelial cells.
 
Notes:
*Most common '''B''' type.
====Type B3====
*Neoplastic cells with some resemblance to cortical epithelial cells.
**Polygonal/round shape.
**Form sheets (of cells) - '''key feature'''.
*Lymphocytes - less than in Type B2.
*AKA ''well-differentiated thymic carcinoma''.
 
Lesion consists of:
*<1/3 lymphocytes, >2/3 cortical epithelial cells.
 
Note:
*Neoplastic cells derived from the thymus with cytologic features of malignancy are [[thymic carcinoma]]s.
 
Images:
<gallery>
Image:Thymoma_type_B1_(1).JPG | Thymoma Type B1. (WC/KGH)
Image:Thymoma_B1_(2).JPG | Thymoma Type B1. (WC/KGH)
Image:Thymoma_B1_(3)_CK_CAM5-2.JPG | Thymoma Type B1 - CAM5.2. (WC/KGH)
</gallery>
 
==Gross==
*Light brown/tan.
*Encapsulated.
 
Image:
*[http://www.sciencephoto.com/media/253251/enlarge Thymoma (sciencephoto.com)].
 
==Microscopic==
Features:
*Lymphocytes.
*Epithelial cells.
**Spindle cells - Type A.
**Epithelioid cells - Type B.
 
DDx:
*[[Squamous cell carcinoma]].
*[[Lymphoma]].
 
Images:
*[http://commons.wikimedia.org/wiki/File:Thymoma_B1_%282%29.JPG Thymoma (WC)].
 
===Staging===
There is a system by Masaoka and colleagues<ref name=pmid7296496 >{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Monden | first2 = Y. | last3 = Nakahara | first3 = K. | last4 = Tanioka | first4 = T. | title = Follow-up study of thymomas with special reference to their clinical stages. | journal = Cancer | volume = 48 | issue = 11 | pages = 2485-92 | month = Dec | year = 1981 | doi =  | PMID = 7296496 }}</ref> that was subsequently modified, and is known as the ''modified Masaoka staging system''.<ref name=pmid8044305>{{Cite journal  | last1 = Koga | first1 = K. | last2 = Matsuno | first2 = Y. | last3 = Noguchi | first3 = M. | last4 = Mukai | first4 = K. | last5 = Asamura | first5 = H. | last6 = Goya | first6 = T. | last7 = Shimosato | first7 = Y. | title = A review of 79 thymomas: modification of staging system and reappraisal of conventional division into invasive and non-invasive thymoma. | journal = Pathol Int | volume = 44 | issue = 5 | pages = 359-67 | month = May | year = 1994 | doi =  | PMID = 8044305 }}</ref>
 
====Based on CAP protocol====
Staging as per Butnor ''et al.'':<ref>Butnor KJ et al. Thymus. Version 3.1.0.0. 2011. URL: [http://www.cap.org/cancerprotocols www.cap.org/cancerprotocols]. Accessed on: 31 August 2015.</ref>
{| class="wikitable sortable"
!Stage
!Characteristics
|-
|I
|encapsulated lesion, tumour does not penetrate capsule
|-
|IIa
|microscopic penetration of the capsule
|-
|IIb
|macroscopic penetration of the capsule
|-
|III
|macroscopic invasion of adjacent organs
|-
|IVa
|pleural or pericardial spread
|-
|IVb
|lymphatic or hematogenous spread
|}
 
====Modified Masaoka as per Masaoka ''et al.'' (1999)====
T-stage - based on Masaoka ''et al.'' (1999):<ref name=pmid10047676>{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Yamakawa | first2 = Y. | last3 = Fujii | first3 = Y. | title = Well-differentiated thymic carcinoma: is it thymic carcinoma or not? | journal = J Thorac Cardiovasc Surg | volume = 117 | issue = 3 | pages = 628-30 | month = Mar | year = 1999 | doi =  | PMID = 10047676 }}</ref>
{| class="wikitable sortable"
!Stage
!Features
|-
| T1
| macroscopically and microscopically encapulated
|-
| T2
| macroscopic invasion or adhesion to surrounding tissue (fat or pleura) ''or'' microscopic invasion into the capsule
|-
| T3
| Spread to adjacent organs, e.g. pericardium, lung, great vessels.
|-
| T4
| pericardial or pleural spread
|}
 
N-stage - based on Masaoka ''et al.'' (1999):<ref name=pmid10047676>{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Yamakawa | first2 = Y. | last3 = Fujii | first3 = Y. | title = Well-differentiated thymic carcinoma: is it thymic carcinoma or not? | journal = J Thorac Cardiovasc Surg | volume = 117 | issue = 3 | pages = 628-30 | month = Mar | year = 1999 | doi =  | PMID = 10047676 }}</ref>
{| class="wikitable sortable"
!Stage
!Features
|-
| N0
| no lymph node spread
|-
| N1
| spread to anterior mediastinal lymph nodes
|-
| N2
| spread to intrathoracic lymph nodes other than the mediastinal lymph nodes
|-
| N3
| spread to supraclavicular lymph nodes
|}
 
M-stage - based on Masaoka ''et al.'' (1999):<ref name=pmid10047676>{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Yamakawa | first2 = Y. | last3 = Fujii | first3 = Y. | title = Well-differentiated thymic carcinoma: is it thymic carcinoma or not? | journal = J Thorac Cardiovasc Surg | volume = 117 | issue = 3 | pages = 628-30 | month = Mar | year = 1999 | doi =  | PMID = 10047676 }}</ref>
{| class="wikitable sortable"
!Stage
!Features
|-
| M0
| no hematogeneous spread and extrathoracic lymph nodes with the exception of the supraclavicular nodes
|-
| M1
| hematogeneous spread and/or extrathoracic lymph nodes 
|}
 
==IHC==
*[[p63]] +ve.<ref name=pmid24923897>{{cite journal |author=Adam P, Hakroush S, Hofmann I, Reidenbach S, Marx A, Ströbel P |title=Thymoma with loss of keratin expression (and giant cells): a potential diagnostic pitfall |journal=Virchows Arch. |volume= |issue= |pages= |year=2014 |month=June |pmid=24923897 |doi=10.1007/s00428-014-1606-6 |url=}}</ref>
*TdT +ve.
*Ki-67 variable.<ref name=pmid24585679>{{Cite journal  | last1 = Viti | first1 = A. | last2 = Bertolaccini | first2 = L. | last3 = Cavallo | first3 = A. | last4 = Fortunato | first4 = M. | last5 = Bianchi | first5 = A. | last6 = Terzi | first6 = A. | title = 18-Fluorine fluorodeoxyglucose positron emission tomography in the pretreatment evaluation of thymic epithelial neoplasms: a metabolic biopsy confirmed by Ki-67 expression. | journal = Eur J Cardiothorac Surg | volume = 46 | issue = 3 | pages = 369-74; discussion 374 | month = Sep | year = 2014 | doi = 10.1093/ejcts/ezu030 | PMID = 24585679 }}</ref>
**~5-70% for A, AB & B1.
**~80-100% for B2 & B3.
 
A panel:
*TdT, CD1a, CD3, CD5, CD20, Ki-67, CD117, p63, CK5/6.
 
==Sign out==
<pre>
A. Lymph Node, Station 6, Lymphadenectomy:
- One benign lymph node (0/1).
 
B. Submitted as "Anterior Mediastinal Tumour (Thymus)", Excision:
- Thymoma, WHO type B2.
- Modified Masaoka stage IIa.
- Three benign lymph nodes (0/3).
- Rim of benign thymus.
- Please see synoptic report.
</pre>
 
==See also==
*[[Thymus]].
 
==References==
{{Reflist|1}}


[[Category:Diagnosis]]
[[Category:Diagnosis]]
[[Category:Haematopathology]]
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