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| [[Image:Thymic corpuscle.jpg|thumb|right|225px|[[Micrograph]] of a thymic corpusle (Hassall's corpusle). [[H&E stain]].]] | | [[Image:Thymic corpuscle.jpg|thumb|right|225px|[[Micrograph]] of a thymic corpusle (Hassall's corpusle). [[H&E stain]].]] |
| '''Thymus''' is an annoying little organ that is in the [[mediastinum]]. It is often removed in pediatric cardiac surgery 'cause it is in the way. In adults, it is commonly removed 'cause the patient has myasthenia gravis. | | '''Thymus''' is a little organ that is in the [[mediastinum]]. It is often removed in pediatric cardiac surgery 'cause it is in the way. In adults, it is commonly removed 'cause the patient has myasthenia gravis. |
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| =Overview= | | =Overview= |
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| *One of two ''[[primary lymphoid organs]]'' - the other one is the [[bone marrow]].<ref>URL: [http://www.life.umd.edu/classroom/bsci423/song/Lab1.html http://www.life.umd.edu/classroom/bsci423/song/Lab1.html]. Accessed on: 28 March 2012.</ref> | | *One of two ''[[primary lymphoid organs]]'' - the other one is the [[bone marrow]].<ref>URL: [http://www.life.umd.edu/classroom/bsci423/song/Lab1.html http://www.life.umd.edu/classroom/bsci423/song/Lab1.html]. Accessed on: 28 March 2012.</ref> |
| *Thymus involutes after childhood. | | *Thymus involutes after childhood. |
| | **The line between ''[[thymoma]]'' and ''persistent normal thymus in the adult'' is not well-defined in the radiologic context.<ref name=pmid25925358>{{Cite journal | last1 = Araki | first1 = T. | last2 = Nishino | first2 = M. | last3 = Gao | first3 = W. | last4 = Dupuis | first4 = J. | last5 = Hunninghake | first5 = GM. | last6 = Murakami | first6 = T. | last7 = Washko | first7 = GR. | last8 = O'Connor | first8 = GT. | last9 = Hatabu | first9 = H. | title = Normal thymus in adults: appearance on CT and associations with age, sex, BMI and smoking. | journal = Eur Radiol | volume = 26 | issue = 1 | pages = 15-24 | month = Jan | year = 2016 | doi = 10.1007/s00330-015-3796-y | PMID = 25925358 }}</ref> |
| *May be absent due to genetic abnormalities, e.g. [[DiGeorge syndrome]]. | | *May be absent due to genetic abnormalities, e.g. [[DiGeorge syndrome]]. |
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| ==IHC and thymus== | | ==IHC and thymus== |
| Types A, AB, B:<ref name=cjs>CJS. January 2010.</ref> | | Types A, AB, B:<ref name=cjs>CJS. January 2010.</ref> |
| *[[CK7]] -ve, [[CK20]] -ve, CAM5.2 +ve, CK5/6 +ve, p63 +ve, CD5 -ve. | | *[[CK7]] -ve, [[CK20]] -ve, CAM5.2 +ve, [[CK5/6]] +ve, [[p63]] +ve, CD5 -ve. |
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| Type C: | | Type C: |
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| ==Thymoma== | | ==Thymoma== |
| ===General===
| | {{Main|Thymoma}} |
| *Strong association with autoimmune disease, esp. myasthenia gravis.
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| ====Classification====
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| The ''WHO'' published a widely used system - WHO classification:<ref>{{Ref Sternberg4|1264}}</ref>
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| =====Type A=====
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| *AKA ''Spindle cell'' or ''medullary''.
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| *Arise from ''medullary epithelial cells''.
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| *Good prognosis.
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| IHC:
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| *Usu. keratin+.
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| =====Type AB=====
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| *Like Type A... but with foci of lymphocytes.
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| =====Type B1=====
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| *Near normal, expanded cortex.
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| Lesion consists of:
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| *>2/3 lymphocytes, <1/3 cortical epithelial cells.
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| =====Type B2=====
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| *Neoplastic cells with some resemblance to cortical epithelial cells.
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| **Epithelioid cells with distinct nucleoli.
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| **May be perivascular.
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| *Large population of lymphocytes.
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| Lesion consists of:
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| *<2/3 but >1/3 lymphocytes, >1/3 but <2/3 cortical epithelial cells.
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| Notes:
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| *Most common '''B''' type.
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| =====Type B3=====
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| *Neoplastic cells with some resemblance to cortical epithelial cells.
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| **Polygonal/round shape.
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| **Form sheets (of cells) - '''key feature'''.
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| *Lymphocytes - less than in Type B2.
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| *AKA ''well-differentiated thymic carcinoma''.
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| Lesion consists of:
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| *<1/3 lymphocytes, >2/3 cortical epithelial cells.
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| Note:
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| *Neoplastic cells derived from the thymus with cytologic features of malignancy are [[thymic carcinoma]]s.
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| Images:
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| <gallery>
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| Image:Thymoma_type_B1_(1).JPG | Thymoma Type B1. (WC/KGH)
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| Image:Thymoma_B1_(2).JPG | Thymoma Type B1. (WC/KGH)
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| Image:Thymoma_B1_(3)_CK_CAM5-2.JPG | Thymoma Type B1 - CAM5.2. (WC/KGH)
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| </gallery>
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| ===Gross===
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| *Light brown/tan.
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| *Encapsulated.
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| Image:
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| *[http://www.sciencephoto.com/media/253251/enlarge Thymoma (sciencephoto.com)].
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| ===Microscopic===
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| Features:
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| *Lymphocytes.
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| *Epithelial cells.
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| **Spindle cells - Type A.
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| **Epithelioid cells - Type B.
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| DDx:
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| *[[Squamous cell carcinoma]].
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| *[[Lymphoma]].
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| Images:
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| *[http://commons.wikimedia.org/wiki/File:Thymoma_B1_%282%29.JPG Thymoma (WC)].
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| ====Staging====
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| 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>
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| =====Based on CAP protocol=====
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| 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>
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| {| class="wikitable sortable"
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| !Stage
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| !Characteristics
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| |-
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| |I
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| |encapsulated lesion, tumour does not penetrate capsule
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| |-
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| |IIa
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| |microscopic penetration of the capsule
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| |-
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| |IIb
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| |macroscopic penetration of the capsule
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| |-
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| |III
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| |macroscopic invasion of adjacent organs
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| |-
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| |IVa
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| |pleural or pericardial spread
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| |-
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| |IVb
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| |lymphatic or hematogenous spread
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| |}
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| =====Modified Masaoka as per Masaoka ''et al.'' (1999)=====
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| 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>
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| {| class="wikitable sortable"
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| !Stage
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| !Features
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| |-
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| | T1
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| | macroscopically and microscopically encapulated
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| |-
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| | T2
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| | macroscopic invasion or adhesion to surrounding tissue (fat or pleura) ''or'' microscopic invasion into the capsule
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| |-
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| | T3
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| | Spread to adjacent organs, e.g. pericardium, lung, great vessels.
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| |-
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| | T4
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| | pericardial or pleural spread
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| |}
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| 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>
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| {| class="wikitable sortable"
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| !Stage
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| !Features
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| |-
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| | N0
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| | no lymph node spread
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| |-
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| | N1
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| | spread to anterior mediastinal lymph nodes
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| |-
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| | N2
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| | spread to intrathoracic lymph nodes other than the mediastinal lymph nodes
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| |-
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| | N3
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| | spread to supraclavicular lymph nodes
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| |}
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| 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>
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| {| class="wikitable sortable"
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| !Stage
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| !Features
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| |-
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| | M0
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| | no hematogeneous spread and extrathoracic lymph nodes with the exception of the supraclavicular nodes
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| |-
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| | M1
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| | hematogeneous spread and/or extrathoracic lymph nodes
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| |}
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| ===IHC===
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| *[[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>
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| *TdT +ve.
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| ==Metaplastic thymoma== | | ==Metaplastic thymoma== |
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| ==Thymic carcinoma== | | ==Thymic carcinoma== |
| *Previously ''Thymic tumour type C''.
| | {{Main|Thymic carcinoma}} |
| ===General===
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| *Rare.
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| *Usually arise ''de novo'', i.e. thymoma is not generally a precursor.
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| *Risk factors - possibly: [[smoking]], radiation.<ref name=pmid23319214/>
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| ===Microscopic===
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| Features:<ref name=Ref_WMSP147>{{Ref WMSP|147}}</ref>
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| *Cytologically malignant - variable morphology.
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| **[[Squamous cell carcinoma]] is the most common (65-73% of cases<ref name=pmid23319214>{{Cite journal | last1 = Thomas de Montpréville | first1 = V. | last2 = Ghigna | first2 = MR. | last3 = Lacroix | first3 = L. | last4 = Besse | first4 = B. | last5 = Broet | first5 = P. | last6 = Dartevelle | first6 = P. | last7 = Fadel | first7 = E. | last8 = Dorfmuller | first8 = P. | title = Thymic carcinomas: clinicopathologic study of 37 cases from a single institution. | journal = Virchows Arch | volume = 462 | issue = 3 | pages = 307-13 | month = Mar | year = 2013 | doi = 10.1007/s00428-013-1371-y | PMID = 23319214 }}</ref><ref name=pmid23866799>{{Cite journal | last1 = Zhao | first1 = Y. | last2 = Zhao | first2 = H. | last3 = Hu | first3 = D. | last4 = Fan | first4 = L. | last5 = Shi | first5 = J. | last6 = Fang | first6 = W. | title = Surgical treatment and prognosis of thymic squamous cell carcinoma: a retrospective analysis of 105 cases. | journal = Ann Thorac Surg | volume = 96 | issue = 3 | pages = 1019-24 | month = Sep | year = 2013 | doi = 10.1016/j.athoracsur.2013.04.078 | PMID = 23866799 }}</ref>).
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| *+/-Squamous differentiation.
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| Notes:
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| *Staging depends on capsular invasion.
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| DDx:
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| *[[Thymoma]].
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| *[[Lung cancer|Lung carcinoma]].
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| *[[Gastrointestinal stromal tumour]].<ref name=pmid23375402>{{Cite journal | last1 = Rossi | first1 = V. | last2 = Donini | first2 = M. | last3 = Sergio | first3 = P. | last4 = Passalacqua | first4 = R. | last5 = Rossi | first5 = G. | last6 = Buti | first6 = S. | title = When a thymic carcinoma becomes a GIST. | journal = Lung Cancer | volume = 80 | issue = 1 | pages = 106-8 | month = Apr | year = 2013 | doi = 10.1016/j.lungcan.2013.01.003 | PMID = 23375402 }}</ref>
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| ====Images====
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| *[http://www.webpathology.com/image.asp?n=1&Case=653 Thymic carcinoma - low mag. (webpathology.com)].
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| *[http://www.webpathology.com/image.asp?n=2&Case=653 Thymic carcinoma - high mag. (webpathology.com)].
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| *[http://www.webpathology.com/image.asp?n=4&Case=653 Thymic carcinoma - lymphoepithelioma-like - high mag. (webpathology.com)].
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| ===IHC===
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| Features:<ref name=Ref_WMSP147>{{Ref WMSP|147}}</ref>
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| *CD5 +ve (90% of cases<ref name=pmid23319214/>).<ref name=Ref_PBoD708>{{Ref PBoD|708}}</ref>
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| *CD117 +ve (87% of cases<ref name=pmid23319214/>).
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| *CD7 +ve.
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| *[[TTF-1]] -ve.
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| Note:
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| *Should stain with keratins.
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| =See also= | | =See also= |