Difference between revisions of "Thymus"

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Thymus (view source)

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'''Thymus''' is an annoying little organ that is in the mediastinum.
'''Thymus''' is an annoying little organ that is in the mediastinum.


==General==
=Overview=
*Involutes after childhood.
*Thymus involutes after childhood.
*Location: anterior mediastinum.
*Location: anterior mediastinum.
*Important for development of the immune system.
*Important for development of the immune system.
*May contain within it parathyroid.<ref name=Ref_PBoD706>{{Ref PBoD|706}}</ref>
*May contain within it parathyroid.<ref name=Ref_PBoD706>{{Ref PBoD|706}}</ref>


==Histology==
 
 
==Normal histology==
===General===
===General===
Features:<ref>URL: [http://www.kumc.edu/instruction/medicine/anatomy/histoweb/lymphoid/lymph03.htm http://www.kumc.edu/instruction/medicine/anatomy/histoweb/lymphoid/lymph03.htm]. Accessed on: 17 June 2010.</ref>
Features:<ref>URL: [http://www.kumc.edu/instruction/medicine/anatomy/histoweb/lymphoid/lymph03.htm http://www.kumc.edu/instruction/medicine/anatomy/histoweb/lymphoid/lymph03.htm]. Accessed on: 17 June 2010.</ref>
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*Other WBCs: B lymphocytes, neutrophils, eosinophils.
*Other WBCs: B lymphocytes, neutrophils, eosinophils.
*Myoid cells.
*Myoid cells.
Note:
*Thymic tumours are derived from the epithelial component of the thymus, i.e. the ''cortical epithelial cells'' and ''medullary epithelial cells''.


Images:
Images:
*[http://commons.wikimedia.org/wiki/File:Thymic_corpuscle.jpg Thymic corpusle (wikimedia.org)].
*[http://commons.wikimedia.org/wiki/File:Thymic_corpuscle.jpg Thymic corpusle (wikimedia.org)].


==IHC and thymus==
Types A, AB, B:<ref>CJS. January 2010.</ref>
*CK7-, CK20-, CAM5.2+, CK5/6+, p63+, CD5-.
Type C:<ref>CJS. January 2010.</ref>
*CD5+.
All types:<ref>CJS. January 2010.</ref>
*CD1a (immature T cells, Langerhans cells, dendritic cells<ref>URL: [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1886385/pdf/amjpathol00102-0156.pdf http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1886385/pdf/amjpathol00102-0156.pdf]. Accessed on: 26 August 2010.</ref>), CEA +ve (focal), vimentin -ve.
Others (immature T cells):
*TdT.
*CD99.
==Anterior mediastinum mass DDx==
{{Main|Mediastinum}}
4 Ts (mnemonic):
*Thymoma.
*Terrible [[lymphoma]].
*[[Teratoma]].
*[[Thyroid]] (ectopic).
=Absence of the thymus=
==Di George syndrome==
==Di George syndrome==
*Things go wrong with the thymus... very wrong.
*Things go wrong with the thymus... very wrong.


==Thymus and stress==
=Thymus and stress=
*Stress -> increased endogenous steroid -> lymphocyte death -> increased tingible body macrophages.<ref>{{cite journal |author=Toti P, De Felice C, Stumpo M, ''et al.'' |title=Acute thymic involution in fetuses and neonates with chorioamnionitis |journal=Hum. Pathol. |volume=31 |issue=9 |pages=1121–8 |year=2000 |month=September |pmid=11014581 |doi= |url=}}</ref>
*Stress -> increased endogenous steroid -> lymphocyte death -> increased tingible body macrophages.<ref>{{cite journal |author=Toti P, De Felice C, Stumpo M, ''et al.'' |title=Acute thymic involution in fetuses and neonates with chorioamnionitis |journal=Hum. Pathol. |volume=31 |issue=9 |pages=1121–8 |year=2000 |month=September |pmid=11014581 |doi= |url=}}</ref>


=Specific conditions=
==Thymic follicular hyperplasia==
==Thymic follicular hyperplasia==
*AKA ''thymic follicular hyperplasia''.
*AKA ''thymic follicular hyperplasia''.
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*Other autoimmune diseases.
*Other autoimmune diseases.


==Tumours of the thymus (overview)==
==Thymoma==
Thymic tumours are derived from the epithelial component of the thymus, i.e. the ''cortical epithelial cells'' and ''medullary epithelial cells''.
===General===
*Strong association with autoimmune disease, esp. myasthenia gravis.


====Classification====
The ''WHO'' published a widely used system - WHO classification:<ref>{{Ref Sternberg4|1264}}</ref>
The ''WHO'' published a widely used system - WHO classification:<ref>{{Ref Sternberg4|1264}}</ref>
===Type A===
=====Type A=====
*AKA ''Spindle cell'' or ''medullary''.
*AKA ''Spindle cell'' or ''medullary''.
*Arise from ''medullary epithelial cells''.
*Arise from ''medullary epithelial cells''.
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IHC:
IHC:
*Usu. keratin+.
*Usu. keratin+.
===Type AB===
=====Type AB=====
*Like Type A... but with foci of lymphocytes.
*Like Type A... but with foci of lymphocytes.
===Type B1===
=====Type B1=====
*Near normal, expanded cortex.
*Near normal, expanded cortex.


Lesion consists of:
Lesion consists of:
*>2/3 lymphocytes, <1/3 cortical epithelial cells.
*>2/3 lymphocytes, <1/3 cortical epithelial cells.
===Type B2===
=====Type B2=====
*Neoplastic cells with some resemblance to cortical epithelial cells.
*Neoplastic cells with some resemblance to cortical epithelial cells.
**Epithelioid cells with distinct nucleoli.
**Epithelioid cells with distinct nucleoli.
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Notes:
Notes:
*Most common '''B''' type.
*Most common '''B''' type.
===Type B3===
=====Type B3=====
*Neoplastic cells with some resemblance to cortical epithelial cells.
*Neoplastic cells with some resemblance to cortical epithelial cells.
**Polygonal/round shape.
**Polygonal/round shape.
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Lesion consists of:
Lesion consists of:
*<1/3 lymphocytes, >2/3 cortical epithelial cells.
*<1/3 lymphocytes, >2/3 cortical epithelial cells.
===Type C===
 
*AKA ''thymic carcinoma''.
Note:
*Neoplastic cells with some resemblance to cortical epithelial cells - with cytologic features of malignancy.
*Neoplastic cells derived from the thymus with cytologic features of malignancy are [[thymic carcinoma]]s.
**Any nuclear atypia of epithelial thymocytes... puts a tumour into this group.


Images:
Images:
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**[http://commons.wikimedia.org/wiki/File:Thymoma_B1_(2).JPG Thymoma Type B1 (WC)].
**[http://commons.wikimedia.org/wiki/File:Thymoma_B1_(2).JPG Thymoma Type B1 (WC)].
**[http://commons.wikimedia.org/wiki/File:Thymoma_B1_(3)_CK_CAM5-2.JPG Thymoma Type B1 - CAM5.2 (WC)].
**[http://commons.wikimedia.org/wiki/File:Thymoma_B1_(3)_CK_CAM5-2.JPG Thymoma Type B1 - CAM5.2 (WC)].
*Type C:
**[http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675(06)70555-1 Thymic carcinoma - Type C (pathconsultddx.com)].
==Thymoma==
===General===
*Strong association with autoimmune disease, esp. myasthenia gravis.


===Microscopic===
===Microscopic===
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There is a system by Masaoka et al..<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>
There is a system by Masaoka et al..<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>


==IHC and thymus==
=See also=
Types A, AB, B:<ref>CJS. January 2010.</ref>
*CK7-, CK20-, CAM5.2+, CK5/6+, p63+, CD5-.
 
Type C:<ref>CJS. January 2010.</ref>
*CD5+.
 
All types:<ref>CJS. January 2010.</ref>
*CD1a (immature T cells, Langerhans cells, dendritic cells<ref>URL: [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1886385/pdf/amjpathol00102-0156.pdf http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1886385/pdf/amjpathol00102-0156.pdf]. Accessed on: 26 August 2010.</ref>), CEA +ve (focal), vimentin -ve.
 
Others (immature T cells):
*TdT.
*CD99.
 
==Anterior mediastinum mass DDx==
4 Ts (mnemonic):
*Thymoma.
*Terrible [[lymphoma]].
*[[Teratoma]].
*[[Thyroid]] (ectopic).
 
==See also==
*[[Thyroid gland]].
*[[Thyroid gland]].
*[[Basics]].
*[[Basics]].
*[[Lung]].
*[[Lung]].


==References==
=References=
{{reflist|2}}
{{reflist|2}}


[[Category:Haematopathology]]
[[Category:Haematopathology]]
Michael
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