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'''Thymus''' is | [[Image:Thymic corpuscle.jpg|thumb|right|225px|[[Micrograph]] of a thymic corpusle (Hassall's corpusle). [[H&E stain]].]] | ||
'''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. | |||
=Overview= | |||
==General== | ==General== | ||
*Important for development of the immune system. | *Important for development of the immune system. | ||
* | *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. | |||
**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]]. | |||
== | ==Anatomy== | ||
Location: | |||
*Anterior [[mediastinum]]. | |||
Anatomically in contact with: | |||
*[[Pericardium]]. | |||
*Medistinal pleural. | |||
==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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**Round eosinophilic thingy. | **Round eosinophilic thingy. | ||
**Thought to arise from medullary epithelial cells (see ''cell types'').<ref name=Ref_PBoD706>{{Ref PBoD|706}}</ref> | **Thought to arise from medullary epithelial cells (see ''cell types'').<ref name=Ref_PBoD706>{{Ref PBoD|706}}</ref> | ||
Note: | |||
*The thymus may contain within it [[parathyroid]].<ref name=Ref_PBoD706>{{Ref PBoD|706}}</ref> | |||
===Cell types=== | ===Cell types=== | ||
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*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==== | |||
<gallery> | |||
Image:Thymic_corpuscle.jpg | Thymic corpusle. (WC/Nephron) | |||
</gallery> | |||
== | ==IHC and thymus== | ||
* | 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. | |||
Type C: | |||
*CD5 +ve.<ref name=cjs>CJS. January 2010.</ref> (???) | |||
*D2-40 +ve.<ref name=pmid24649128>{{Cite journal | last1 = Yokota | first1 = K. | last2 = Tateyama | first2 = H. | last3 = Yano | first3 = M. | last4 = Moriyama | first4 = S. | last5 = Hikosaka | first5 = Y. | last6 = Okuda | first6 = K. | last7 = Shitara | first7 = M. | last8 = Okumura | first8 = M. | last9 = Yokoi | first9 = K. | title = Clinicopathological analysis of small-sized thymoma with podoplanin and Ki 67 expression analysis. | journal = Mol Clin Oncol | volume = 1 | issue = 1 | pages = 88-92 | month = Jan | year = 2013 | doi = 10.3892/mco.2012.2 | PMID = 24649128 }}</ref> | |||
All types:<ref name=cjs>CJS. January 2010.</ref> | |||
*CD1a +ve (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 +ve. | |||
*CD99 +ve. | |||
==Anterior mediastinum mass DDx== | |||
{{Main|Mediastinum}} | |||
4 Ts (mnemonic): | |||
*Thymoma. | |||
*Terrible [[lymphoma]]. | |||
*[[Teratoma]]. | |||
*[[Thyroid]] (ectopic). | |||
==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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Associations:<ref name=Ref_PBoD707-8>{{Ref PBoD|707-8}}</ref> | Associations:<ref name=Ref_PBoD707-8>{{Ref PBoD|707-8}}</ref> | ||
*Myasthenia gravis. | *Myasthenia gravis. | ||
*Graves' | *[[Graves' disease]]. | ||
*[[Systemic lupus erythematosus]] (SLE). | *[[Systemic lupus erythematosus]] (SLE). | ||
*[[Rheumatoid arthritis]]. | *[[Rheumatoid arthritis]]. | ||
*Other autoimmune diseases. | *Other [[autoimmune diseases]]. | ||
== | ==Thymoma== | ||
{{Main|Thymoma}} | |||
==Metaplastic thymoma== | |||
*[[AKA]] ''thymoma with pseudosarcomatous stroma''.<ref name=metapl_thy/> | |||
===General=== | ===General=== | ||
* | *Extremely rare - only 17 case reports as of 2011.<ref name=pmid20034984>{{Cite journal | last1 = Lu | first1 = HS. | last2 = Gan | first2 = MF. | last3 = Zhou | first3 = T. | last4 = Wang | first4 = SZ. | title = Sarcomatoid thymic carcinoma arising in metaplastic thymoma: a case report. | journal = Int J Surg Pathol | volume = 19 | issue = 5 | pages = 677-80 | month = Oct | year = 2011 | doi = 10.1177/1066896909355458 | PMID = 20034984 }}</ref> | ||
*Two reports of transformation into [[thymic carcinoma]].<ref name=pmid20034984/> | |||
===Microscopic=== | ===Microscopic=== | ||
Features: | Features:<ref name=metapl_thy>URL: [http://surgpathcriteria.stanford.edu/thymus/thymoma/metaplastic_thymoma.html http://surgpathcriteria.stanford.edu/thymus/thymoma/metaplastic_thymoma.html]. Accessed on: 22 December 2011.</ref> | ||
#Epithelioid cells. | |||
#Spindle cells. | |||
*Few lymphocytes. | |||
DDx: | DDx: | ||
*[[ | *[[Thymic carcinoma]] with sarcomatoid differentiation. | ||
== | ====Images==== | ||
www: | |||
*[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3479700/figure/F1/ Metaplastic thymoma (nih.gov)].<ref>{{Cite journal | last1 = Kang | first1 = G. | last2 = Yoon | first2 = N. | last3 = Han | first3 = J. | last4 = Kim | first4 = YE. | last5 = Kim | first5 = TS. | last6 = Kim | first6 = K. | title = Metaplastic thymoma: report of 4 cases. | journal = Korean J Pathol | volume = 46 | issue = 1 | pages = 92-5 | month = Feb | year = 2012 | doi = 10.4132/KoreanJPathol.2012.46.1.92 | PMID = 23109986 }} | |||
</ref> | |||
*[http://www. | |||
===IHC=== | ===IHC=== | ||
CD5 -ve.<ref name=metapl_thy>URL: [http://surgpathcriteria.stanford.edu/thymus/thymoma/metaplastic_thymoma.html http://surgpathcriteria.stanford.edu/thymus/thymoma/metaplastic_thymoma.html]. Accessed on: 22 December 2011.</ref> | |||
== | ==Thymic carcinoma== | ||
{{Main|Thymic carcinoma}} | |||
=See also= | |||
*[[Thyroid gland]]. | *[[Thyroid gland]]. | ||
*[[Basics]]. | *[[Basics]]. | ||
*[[Lung]]. | *[[Lung]]. | ||
=References= | |||
{{reflist|2}} | {{reflist|2}} | ||
[[Category:Haematopathology]] | [[Category:Haematopathology]] |
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