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| ==Merkel cell carcinoma== | | ==Merkel cell carcinoma== |
| *Abbreviated ''MCC''.
| | {{Main|Merkel cell carcinoma}} |
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| ===General===
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| Features:<ref name=pmid20418670>{{Cite journal | last1 = Calder | first1 = KB. | last2 = Smoller | first2 = BR. | title = New insights into merkel cell carcinoma. | journal = Adv Anat Pathol | volume = 17 | issue = 3 | pages = 155-61 | month = May | year = 2010 | doi = 10.1097/PAP.0b013e3181d97836 | PMID = 20418670 }}</ref>
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| *Rare.
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| *Aggressive course/poor prognosis.
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| *Neuroendocrine-like.<ref name=pmid19395876>{{Cite journal | last1 = Pulitzer | first1 = MP. | last2 = Amin | first2 = BD. | last3 = Busam | first3 = KJ. | title = Merkel cell carcinoma: review. | journal = Adv Anat Pathol | volume = 16 | issue = 3 | pages = 135-44 | month = May | year = 2009 | doi = 10.1097/PAP.0b013e3181a12f5a | PMID = 19395876 }}
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| </ref>
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| Etiology:
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| *Most caused by ''Merkel cell [[polyomavirus]]''.<ref name=pmid18202256>{{Cite journal | last1 = Feng | first1 = H. | last2 = Shuda | first2 = M. | last3 = Chang | first3 = Y. | last4 = Moore | first4 = PS. | title = Clonal integration of a polyomavirus in human Merkel cell carcinoma. | journal = Science | volume = 319 | issue = 5866 | pages = 1096-100 | month = Feb | year = 2008 | doi = 10.1126/science.1152586 | PMID = 18202256 }}</ref><ref name=pmid20418670/>
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| *Immunocompromised/immunosuppressed (e.g. organ transplant recipients).
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| ===Microscopic===
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| Features:<ref name=Ref_WMSP491>{{Ref WMSP|491}}</ref>
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| *Neuroendocrine nuclear features - round nucleus, small nucleoli/no nucleolus, stippled chromatin - '''key feature'''.
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| *Typically medium size cells ~3x resting lymphocyte.
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| **May be small or large.
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| *Architecture: nests, sheets or trabeculae.
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| *Scant cytoplasm.
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| *Abundant mitoses. †
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| *+/-Nuclear moulding.
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| **Nuclei of adjacent cells conform to one another.
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| *+/-Tumour infiltrating lymphocytes. ‡
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| Notes:
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| *† >10 mitoses/HPF = poor prognosis - definition suffers from [[HPFitis]].<ref name=capp_mcc>URL: [http://www.cap.org/apps/docs/committees/cancer/cancer_protocols /2011/SkinMerkelCell_11protocol.pdf http://www.cap.org/apps/docs/committees/cancer/cancer_protocols/2011/SkinMerkelCell_11protocol.pdf]. Accessed on: 28 March 2012.</ref>
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| *‡ May be associated with a worse prognosis.<ref name=capp_mcc/>
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| *Merkel cell carcinoma [[lymph node metastases]] is difficult to diagnose with routine stains; use of IHC stains are advised.<ref name=capp_mcc/>
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| *Arise from the epidermis - very rarely in situ.<ref name=pmid15606676>{{Cite journal | last1 = Ferringer | first1 = T. | last2 = Rogers | first2 = HC. | last3 = Metcalf | first3 = JS. | title = Merkel cell carcinoma in situ. | journal = J Cutan Pathol | volume = 32 | issue = 2 | pages = 162-5 | month = Feb | year = 2005 | doi = 10.1111/j.0303-6987.2005.00270.x | PMID = 15606676 }}</ref>
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| DDx:
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| *[[Basal cell carcinoma]] - no stippled chromatin, less mitoses active.
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| *Cutaneous [[Ewing sarcoma]] - sorted-out with immunostains.
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| *[[Lymphoma]].
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| **[[Burkitt lymphoma]].
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| *Metastatic [[small cell carcinoma]].
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| *Other [[small round cell tumours]].
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| ====Images====
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| <gallery>
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| Image:Merkel_cell_carcinoma_-_intermed_mag.jpg | MCC - intermed. mag. (WC/Nephron)
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| Image:Merkel_cell_carcinoma_-_very_high_mag.jpg | MCC - very high mag. (WC/Nephron)
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| Image:Merkelcellcarcinoma_Tag.jpg | Merkel cell carcinoma - nested pattern (WC)
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| </gallery>
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| www:
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| *[http://www.bccancer.bc.ca/HPI/CE/cytotechnology/cytosleuthquiz/nongyne/ng12hist.htm MCC (bccancer.bc.ca)].
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| *[http://www.joplink.net/prev/200403/07.html MCC (joplink.net)].
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| *[http://www.ispub.com/ispub/ijd/volume_5_number_2_8/concurrent_merkel_cell_carcinoma_and_bowen_s_disease_of_the_thigh/bowen-fig3.jpg Merkel cell carcinoma (ispub.com)].
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| *[http://path.upmc.edu/cases/case398.html Merkel cell carcinoma - several images (upmc.edu)].
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| ===IHC===
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| Features:
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| *CK7 -ve.
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| *CK20 +ve (perinuclear dot-like).<ref name=pmid11533085>{{Cite journal | last1 = Leech | first1 = SN. | last2 = Kolar | first2 = AJ. | last3 = Barrett | first3 = PD. | last4 = Sinclair | first4 = SA. | last5 = Leonard | first5 = N. | title = Merkel cell carcinoma can be distinguished from metastatic small cell carcinoma using antibodies to cytokeratin 20 and thyroid transcription factor 1. | journal = J Clin Pathol | volume = 54 | issue = 9 | pages = 727-9 | month = Sep | year = 2001 | doi = | PMID = 11533085 | URL = http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1731517/ }}</ref>
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| *CAM5.2 +ve (dot-like pattern).
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| *CD56 +ve.
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| *AE1/AE3 +ve.
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| *Merkel cell polyomavirus +ve ~85% of cases.<ref name=pmid21870327>{{Cite journal | last1 = Jung | first1 = HS. | last2 = Choi | first2 = YL. | last3 = Choi | first3 = JS. | last4 = Roh | first4 = JH. | last5 = Pyon | first5 = JK. | last6 = Woo | first6 = KJ. | last7 = Lee | first7 = EH. | last8 = Jang | first8 = KT. | last9 = Han | first9 = J. | title = Detection of Merkel cell polyomavirus in Merkel cell carcinomas and small cell carcinomas by PCR and immunohistochemistry. | journal = Histol Histopathol | volume = 26 | issue = 10 | pages = 1231-41 | month = Oct | year = 2011 | doi = | PMID = 21870327 }}</ref>
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| Others:
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| *TTF-1 -ve.
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| *NSE +ve.<ref name=pmid15606676/>
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| ===EM===
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| *''[[Neurosecretory granules]]'' ([[AKA]] dense-core granules).<ref name=pmid9062165>{{Cite journal | last1 = Gil-Moreno | first1 = A. | last2 = Garcia-Jiménez | first2 = A. | last3 = González-Bosquet | first3 = J. | last4 = Esteller | first4 = M. | last5 = Castellví-Vives | first5 = J. | last6 = Martínez Palones | first6 = JM. | last7 = Xercavins | first7 = J. | title = Merkel cell carcinoma of the vulva. | journal = Gynecol Oncol | volume = 64 | issue = 3 | pages = 526-32 | month = Mar | year = 1997 | doi = | PMID = 9062165 }}</ref>
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| ==Eccrine carcinoma== | | ==Eccrine carcinoma== |