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'''Soft tissue tumours''' strike fear in many pathologists as they are uncommon and may be difficult to diagnose.
'''Soft tissue lesions''' strike fear in many pathologists as they are uncommon and may be difficult to diagnose. Malignant soft tissue lesions, i.e. [[cancer|cancerous]] soft tissue lesions, are usually '''sarcomas'''. Sarcomas are malignancies derived from mesenchymal tissue. 


==WHO classification of soft tissue tumours==
=Introduction=
===Morphologic grouping<ref>WMSP PP.601-3.</ref>===
==WHO classification of soft tissue lesions/tumours==
#Adipocytic tumours.
===Morphologic grouping===
#Fibroblastic/myofibroblastic tumours.
These include:<ref name=Ref_WMSP601-3>{{Ref WMSP|601-3}}</ref>
#"Fibrohistiocytic" tumours.
#[[Adipocytic tumours]].
#Smooth muscle tumours.
#[[Fibroblastic/myofibroblastic tumours]].
#Skeletal muscle tumours.
#[[Fibrohistiocytic tumours|"Fibrohistiocytic" tumours]].
#Vascular tumours.
#[[Smooth muscle tumours|Smooth muscle tumours]].
#Perivascular (pericytic) tumours.
#[[Soft tissue lesions#Skeletal muscle tumours|Skeletal muscle tumours]].
#Chondro-osseous tumours.
#[[Vascular tumours]].
#Tumours of uncertain differentiation.
#[[Soft_tissue_lesions#Perivascular_tumours|Perivascular (pericytic) tumours]].
#[[Chondro-osseous tumours]].
#[[Soft tissue lesions#Tumours of uncertain differentiation|Tumours of uncertain differentiation]].


===Biologic potential grouping<ref>WMSP PP.598-604.</ref>===
===Biologic potential grouping===
These include:<ref>{{Ref WMSP|598-604}}</ref>
#Benign.
#Benign.
#Intermediate (locally aggressive).
#Intermediate (locally aggressive).
Line 19: Line 22:
#Malignant.
#Malignant.


=Adipocytic tumours=
==Prevalence==
==Hibernoma==
*All sarcomas are rare buggers. 
===General===
**As the classification has been changing over the past years (with more subtypes being recognized/identified) numbers are variable from study-to-study.
*Consists of ''brown fat'' (present in the infants to generate heat).<ref>WMSP P.605.</ref>
*Once upon a time almost everything was called ''malignant fibrous histiocytoma''; thus, it is listed as a common entity in some publications.
*Benign.
*Usually asymptomatic.<ref name=pmid19131775>{{cite journal |author=Ahmed SA, Schuller I |title=Pediatric hibernoma: a case review |journal=J. Pediatr. Hematol. Oncol. |volume=30 |issue=12 |pages=900–1 |year=2008 |month=December |pmid=19131775 |doi=10.1097/MPH.0b013e318184e6dd |url=}}</ref>


===Epidemiology===
Most common:<ref name=pmid17976362>{{cite journal |author=Skubitz KM, D'Adamo DR |title=Sarcoma |journal=Mayo Clin. Proc. |volume=82 |issue=11 |pages=1409–32 |year=2007 |month=November |pmid=17976362 |doi= |url= http://www.mayoclinicproceedings.com/content/82/11/1409.long}}</ref>
*Young adults.
*Liposarcoma.
*Leiomyosarcoma.


===Gross===
==Molecular testing==
*Well-circumscribed.
{{Main|Molecular pathology}}
*Lobulated and light-brown on sectioning.
*Molecular testing plays an important role in soft tissue pathology.
*It is generally seen as an adjunct test that:<ref name=pmid11454050>{{cite journal |author=Fletcher CD, Fletcher JA, Dal Cin P, Ladanyi M, Woodruff JM |title=Diagnostic gold standard for soft tissue tumours: morphology or molecular genetics? |journal=Histopathology |volume=39 |issue=1 |pages=100–3 |year=2001 |month=July |pmid=11454050 |doi= |url=}}</ref>
**Often is used to confirm the histomorphologic impression/quality control.
**Frequently has some prognostic significance.
**May directly affect treatment.


===Microscopic===
===Translocations===
Features:<ref>{{cite journal |author=Chen DY, Wang CM, Chan HL |title=Hibernoma. Case report and literature review |journal=Dermatol Surg |volume=24 |issue=3 |pages=393–5 |year=1998 |month=March |pmid=9537018 |doi= |url=}}</ref>
{{Main|Chromosomal translocations}}
*Large polygonal/oval cells:
*Many tumours in soft tissue pathology are diagnosed inconjunction with the finding of [[chromosomal translocations]].
**Nucleus - central & small.<ref>[http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675(06)70271-6 http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675(06)70271-6]</ref>
***Nucleoli typically prominent.<ref>[http://surgpathcriteria.stanford.edu/softfat/hibernoma/ http://surgpathcriteria.stanford.edu/softfat/hibernoma/]</ref>
**Cytoplasm - multivacuolated, oval, eosinophilic, granular.


Image:
==Morphohistologic patterns==
*[http://en.wikipedia.org/wiki/File:Hibernoma1.jpg Hibernoma (WC)].
{{Main|Morphologic patterns}}
{| class="wikitable sortable" style="margin-left:auto;margin-right:auto"
! Name
! Description
! DDx
! Image(s)
|-
| Storiform, [[AKA]] patternless pattern<ref name=pmid9704618>{{cite journal |author=Mangano WE, Cagle PT, Churg A, Vollmer RT, Roggli VL |title=The diagnosis of desmoplastic malignant mesothelioma and its distinction from fibrous pleurisy: a histologic and immunohistochemical analysis of 31 cases including p53 immunostaining |journal=Am. J. Clin. Pathol. |volume=110 |issue=2 |pages=191–9 |year=1998 |month=August |pmid=9704618 |doi= |url=}}</ref>
| whorled, cartwheel-like arrangement
| [[pleomorphic undifferentiated sarcoma]], [[solitary fibrous tumour]], [[dermatofibrosarcoma protuberans]], [[dermatofibroma]]<ref name=pmid224569>{{cite journal |author=Meister P, Höhne N, Konrad E, Eder M |title=Fibrous histiocytoma: an analysis of the storiform pattern |journal=Virchows Arch A Pathol Anat Histol |volume=383 |issue=1 |pages=31–41 |year=1979 |month=July |pmid=224569 |doi= |url=}}</ref>
| [[Image:Storiform_pattern_-_intermed_mag.jpg |thumb|center|150px| Patternless pattern. (WC)]]
|-
| Herring bone
| like herring bone (technique) for climbing a hill in cross country skiing; books on a shelf, where they have partially fallen over -- on the one shelf to the left and the one below to the right
| [[fibrosarcoma]], [[synovial sarcoma]], [[MPNST]]
| [[Image:Malignant_peripheral_nerve_sheath_tumour_-_intermed_mag.jpg |thumb|center|150px |Herring bone. (WC)]]
|-
| Fascicular
| the long axis of the (spindle) cells are perpendicular to one another in adjacent bundles of cells
| [[leiomyoma]], [[leiomyosarcoma]]
| [[Image:Cutaneous_leiomyosarcoma_-_high_mag.jpg |thumb|center|150px| Fascicular pattern. (WC)]]
|-
| Biphasic
| nests of cells and stroma
| [[synovial sarcoma]], [[DSRCT]], [[alveolar RMS]]
| [[Image:Desmoplastic_small_round_cell_tumour_-_high_mag.jpg|thumb|center|150px| DSRCT. (WC)]]
|- <!--
| name ?
| description ?
| DDx ?
| image ? -->
|}


==Liposarcoma==
Notes:
*Most common malignant sarcoma in the retroperitoneum.
*Memory device: herring bone DDx ''MSF'' = MPNST, Synovial sarcoma, Fibrosarcoma.


===Microscopy===
==Grading==
Features:
*Several systems exist.
*Lipoblasts:
*The US-CAP advocates the use of the French system over the NCI system.
**Large sharply demarcated vacuole.
**The French system is a better predictor metastases and mortality.<ref name=pmid8996162>{{cite journal |author=Guillou L, Coindre JM, Bonichon F, ''et al.'' |title=Comparative study of the National Cancer Institute and French Federation of Cancer Centers Sarcoma Group grading systems in a population of 410 adult patients with soft tissue sarcoma |journal=J. Clin. Oncol. |volume=15 |issue=1 |pages=350–62 |year=1997 |month=January |pmid=8996162 |doi= |url=}}</ref>
**Nucleus:
***Hyperchromatic (dark staining) nucleus.
***Eccentric location.
***Nuclear indentation.


Images:
===French system===
*[http://commons.wikimedia.org/wiki/File:Myxoid_liposarcoma_%2806%29.JPG Myxoid liposarcoma (WC)].
*Formally known as the grading system from the ''French Federation of Cancer Centres Sarcoma Group'' (FNCLCC).
*[http://commons.wikimedia.org/wiki/File:Myxoid_liposarcoma_%2805%29.JPG Myxoid liposarcoma (WC)].
*[http://www.john-libbey-eurotext.fr/e-docs/00/04/09/14/texte_alt_jleejd00046_gr5.jpg Lipoblasts (john-libbey-eurotext.fr)].


===IHC===
====Overview====
*IHC is of limited value.
Components - overview:<ref name=pmid8996162/><ref name=uscap_stp>URL: [http://www.cap.org/apps/docs/committees/cancer/cancer_protocols/2011/SoftTissue_11protocol.pdf http://www.cap.org/apps/docs/committees/cancer/cancer_protocols/2011/SoftTissue_11protocol.pdf]. Accessed on: 12 April 2011.</ref>
#Differentiation (score 1-3).
#*De facto, this is mostly the ''histologic type''.
#Mitotic rate (score 1-3).
#Necrosis (score 0-2)


*S-100 +ve ~1/3 of the time.
Obtaining a score:
*Reticulin ???.
*Add all the points from the three components.


=Smooth muscle tumours=
Scoring:
==Leiomyosarcoma==
*Grade 1 = 2-3.
See gyne notes.
*Grade 2 = 4-5.
*Grade 3 = 6-8.


===Microscopy===
=====Differentiation=====
Features:
*Standardized for histologic types.
*Nuclear atypia.
*Most tumours = 3/3.
*Necrosis.
*Mitoses.


=Fibroblastic/myofibroblastic tumours=
Exceptions:<ref name=uscap_stp/>
*Well-differentiated liposarcoma = 1.
*Myxoid liposarcoma = 2.
*Conventional [[liposarcoma]] = 2.
*Fibrosarcoma = 2.
*[[Myxofibrosarcoma]] =2.


==Proliferative fasciitis==
A group of tumours is not graded:<ref name=uscap_stp/>
*Need to write something here.
*[[MPNST]].
*[[Rhabdomyosarcoma]].
*[[Alveolar soft part sarcoma]].
*[[Clear cell sarcoma]].
*[[Extraskeletal myxoid chondrosarcoma]].


==Hemangiopericytoma==
=====Mitotic rate=====
===General===
*0-9 mitoses/10 HPF.
*Grouped with ''solitary fibrous tumour'' in the WHO classification; possibly the same tumour (?).<ref>WMSP P.609.</ref>
*10-19 mitoses/10 HPF.
*Arises from the ''pericyte'', a connective tissue cell of small vessels that is thought to be involved in flow regulation.
*>=20 mitoses/10 HPF.
*Hematologic spread most common - to lungs.<ref>URL: [http://emedicine.medscape.com/article/1255879-overview http://emedicine.medscape.com/article/1255879-overview]. Accessed on: 2 May 2010.</ref>
*Oncogenic osteomalacia - assoc. with hemangiopericytoma.<ref>URL: [http://emedicine.medscape.com/article/1255879-overview http://emedicine.medscape.com/article/1255879-overview]. Accessed on: 2 May 2010.</ref>


===Presentation===
Notes:
*Usually painless mass, slow enlargement.
*1 HPF = 0.1734 mm^2.
**Most resident microscopes have a field of view = 0.2376 mm^2.
***Thus, ~7.3 HPFs on a resident microscope corresponds to 10 US-CAP HPFs.


====Radiology====
=====Necrosis=====
*Intramedullary lytic mass.
*None = score 0.
*May be well-circumscribed.
*<=50% of tumour = score 1.
*+/-Periosteal reaction.
*>50% of tumour = score 2.
*+/-Sclerotic border.


May be worked-up with angiography to distinguish from a vascular malformation.<ref>URL: [http://emedicine.medscape.com/article/1255879-diagnosis http://emedicine.medscape.com/article/1255879-diagnosis]. Accessed on: 2 May 2010.</ref>
===System used by some at MSH===
===Location===
Some pathologists at [[MSH]] use the system advocated by Costa et al..<ref name=pmid6692258>{{cite journal |author=Costa J, Wesley RA, Glatstein E, Rosenberg SA |title=The grading of soft tissue sarcomas. Results of a clinicohistopathologic correlation in a series of 163 cases |journal=Cancer |volume=53 |issue=3 |pages=530–41 |year=1984 |month=February |pmid=6692258 |doi= |url=}}</ref>
*Usually extremities - femur or prox. tibial.<ref>URL: [http://emedicine.medscape.com/article/1255879-overview http://emedicine.medscape.com/article/1255879-overview]. Accessed on: 2 May 2010.</ref>


===Histology===
====Scoring====
Features:<ref>URL: [http://emedicine.medscape.com/article/1255879-diagnosis http://emedicine.medscape.com/article/1255879-diagnosis]. Accessed on: 2 May 2010.</ref>
*Grade 1 = 1 point.
*Hypervascular lesion - '''key diagnostic feature'''.<ref name=enzinger>Enzinger & Weiss's Soft Tissue Tumors. 4th Ed. PP.1007-13. ISBN 0-323-01200-0.</ref>
*Grade 2 = 2 points.
**Abundant thin-walled branching small vessels of variable size.
*Grade 3 = 3-4 points.
***May be described as "staghorn vessels" or "antler-like" vasculature.
***Cells may "onion-skin" around thin blood vessels.
*Spindle or ovoid shaped cells in nests or sheets.


===IHC===
====Components====
Features:<ref>WMSP P.609.</ref><ref name=enzinger/>
Points for each of the following:
*Vimentin +ve (usually).
*Mitotic activity >= 6 / 10 HPF @ 40X - definition suffers from [[HPFitis]].
*Desmin -ve (typical).
*Pleomorphism present.
*Factor VIII -ve (marks endothelium).
*Cellularity (cells/matrix) > 50%.
*CD34 +ve.
*Necrosis >15% - microscopic (without targeting necrosis grossly) ''or'' grossly.
**CD34 usu. -ve in synovial sarcoma.
*CD31 -ve (marks benign endothelium).
*vWF (von Willebrand factor) -ve.


===DDx===
==Stage==
*Other vascular tumours.
{{Main|Cancer staging systems}}
*Vascular malformations.
===Lymph node metastases in sarcomas===
*Synovial sarcoma.
{{Main|Lymph node metastasis}}
*[[Lymph node]] (LN) spread is uncommon in sarcomas; [[lymph node metastases]] are seen in <3% of cases.<ref name=pmid8424704>{{Cite journal  | last1 = Fong | first1 = Y. | last2 = Coit | first2 = DG. | last3 = Woodruff | first3 = JM. | last4 = Brennan | first4 = MF. | title = Lymph node metastasis from soft tissue sarcoma in adults. Analysis of data from a prospective database of 1772 sarcoma patients. | journal = Ann Surg | volume = 217 | issue = 1 | pages = 72-7 | month = Jan | year = 1993 | doi =  | PMID = 8424704 | PMC = 1242736}}</ref>
**Many sarcomas are reported in LNs.
***According to the [[CAP checklist]] for soft tissue<ref>URL: [http://www.cap.org/apps/docs/committees/cancer/cancer_protocols/2011/SoftTissue_11protocol.pdf http://www.cap.org/apps/docs/committees/cancer/cancer_protocols/2011/SoftTissue_11protocol.pdf]. Accessed on: 28 March 2012.</ref> the most common are: [[epithelioid sarcoma]] and [[clear cell sarcoma]].
***According to Fong ''et al.''<ref name=pmid8424704/> the most commonly is: angiosarcoma.


==Desmoplastic fibroblastoma==
Sarcomas more likely to be found in the lymph nodes - mnemonic ''RACE For MS'':<ref>URL: [http://www.aippg.net/forum/f21/surgery-mnemonics-79897/ http://www.aippg.net/forum/f21/surgery-mnemonics-79897/]. Accessed on: 23 March 2012.</ref>
*AKA ''collagenous fibroma''.<ref name=pmid18271804>PMID 18271804.</ref>
*[[rhabdomyosarcoma|'''R'''habdomyosarcoma]]
*Benign lesion.
*[[Angiosarcoma|'''A'''ngiosarcoma]].
*Classically found in shoulder region.
*[[clear cell sarcoma|'''C'''lear cell sarcoma]].
*[[epithelioid sarcoma|'''E'''pitheliod sarcoma]].
*[[fibrosarcoma|'''F'''ibrosarcoma]].
*[[pleomorphic undifferentiated sarcoma|'''M'''alignant fibrous histiocytoma (pleomorphic undifferentiated sarcoma)]].
*[[synovial sarcoma|'''S'''ynovial cell sarcoma]].


===IHC===
==DDx by history/site==
*Beta-catenin -ve.<ref name=pmid18544056>PMID 18544056.</ref>
===Retroperiteum===
**Significance ???
#[[Liposarcoma]].
#[[Undifferentiated pleomorphic sarcoma]].
#[[Leiomyosarcoma]].
#[[MPNST]].


=Vascular tumours=
Note:
==Hemangioendothelioma==
[[Synovial sarcoma]] and [[fibrosarcoma]] are very rare in the retroperitoneum.
*Usually benign.


===Microscopic===
===Young person - extremity sarcoma===
Features:<ref>Klatt. AOP P.23.</ref>
#[[Epithelioid sarcoma]].
*Well-formed thin vascular channels on a fibrous stroma - '''key feature'''.
#[[Synovial sarcoma]].
*+/-Thrombosis.
*+/-Calcification.
*+/-Fibrosis.
*+/-Myxoid change.


===IHC===
==Gross characteristics==
*Factor VIII +ve.
*Usually non-specific.
*Most sarcomas have a pushing border.
**If there is an infiltrative border think: (1) fibromatosis, (2) carcinoma.


=Other=
=Adipocytic tumours=
==Neurofibromatosis==
{{Main|Adipocytic tumours}}
Comes in two flavours:
#NF1 (peripheral).
#NF2 (central).


===NF1===
This category includes:
Features (need 2/7 to diagnose):<ref>URL: [http://emedicine.medscape.com/article/1177266-overview http://emedicine.medscape.com/article/1177266-overview]. Accessed on: 3 May 2010.</ref>
*Lipoma.
*Two or more neurofibromas or one plexiform neurofibroma.
*Liposarcoma.
*Café-au-lait spots.
*Hibernoma.
*Freckles in axilla or inguinal area.
*Optic nerve glioma.
*Iris hamartomas (Lisch nodules).
*Sphenoid dysplasia or typical long-bone abnormalities (e.g. bowing).
*First-degree relative with NF1.


===NF2===
=Smooth muscle tumours=
Features (need 1/3 to diagnose):<ref>URL: [http://emedicine.medscape.com/article/1178283-overview http://emedicine.medscape.com/article/1178283-overview]. Accessed on: 3 May 2010.</ref>
{{Main|Smooth muscle tumours}}
#Bilateral CNVIII masses on imaging.
IHC markers: desmin, SMA, H-caldemsin (most specific).
#Unilateral CNVIII mass + first-degree relative with NF2.
#First-degree relative with NF2 ''and'' 2/4 of the following:   
## Meningioma.
## Glioma.
## Schwannoma.
## Juvenile cataract.


==Small round blue cell tumours (SRBCT)==
==Leiomyosarcoma==
A group of tumours that has a similar histologic appearance.  It is a group of tumours that is seen more often in childhood than adulthood.
{{Main|Leiomyosarcoma}}


===DDx===
===Microscopic===
*Neuroblastoma.
Features (summary):
*Wilm's tumour.
*Fasicular cellular spindle cell lesion with:
*Alveolar rhabdomyosarcoma.
**Nuclear atypia.
*Ewing sarcoma/PNET - this entity is dealt with in the ''[[bone]]'' article.
**[[Necrosis]].
*Lymphoma (diffuse large B cell lymphoma).
**High mitotic rate.
*Retinoblastoma.
 
*Hepatoblastoma.
=Fibrohistiocytic tumours=
*Desmoplastic small round cell tumour.
''Fibrohistiocytic'' refers (only) to the histomorphologic appearance and therefore may be written in quotation marks; these tumours are not derived from histiocytes (or tissue macrophages), as the name implies.<ref name=pmid20055912>{{Cite journal  | last1 = Luzar | first1 = B. | last2 = Calonje | first2 = E. | title = Cutaneous fibrohistiocytic tumours - an update. | journal = Histopathology | volume = 56 | issue = 1 | pages = 148-65 | month = Jan | year = 2010 | doi = 10.1111/j.1365-2559.2009.03447.x | PMID = 20055912 }}</ref>


===Microscopic===
==Pleomorphic undifferentiated sarcoma==
Features:
*Abbreviated ''PUS''.
*Sheets of cells, very cellular.
*[[AKA]] ''Undifferentiated pleomorphic sarcoma'', abbreviated ''UPS''.
*Small cells ~ 2X RBC diameter.
*Previously known as ''malignant fibrous histiocytoma'', abbreviated ''MFH''.<ref>URL: [http://sarcomahelp.org/learning_center/mfh.html http://sarcomahelp.org/learning_center/mfh.html]. Accessed on: 8 April 2011.</ref>
*Scant cytoplasm.
{{Main|Pleomorphic undifferentiated sarcoma}}
*Coarse chromatin.
*Nucleolus (???).
*+/-Vascular.


==Kaposi sarcoma==
=Fibroblastic/myofibroblastic tumours=
===General===
{{Main|Fibroblastic/myofibroblastic tumours}}
*Not really a sarcoma.
*Caused by HHV-8.
*Associated with immunodeficiency, e.g. HIV/AIDS.


===Stages===
This is a very large and important group of soft tissue lesions.  It is covered in a separate article.
It is seen in different stages:<ref>URL: [http://www.histopathology-india.net/KS.htm http://www.histopathology-india.net/KS.htm]. Accessed on: 31 January 2010.</ref>
#Patch stage.
#Plaque stage.
#Nodular stage.
#Lymphangioma-like. (???)


===Microscopic===
The grouping includes:
Features:<ref>Klatt. AOP P.23.</ref>
*[[Inflammatory myofibroblastic tumour]].
*Vascular channels that anastomose.
*[[Nodular fasciitis]].
*+/-Nuclear atypia.
*[[Desmoid-type fibromatosis]] (Desmoid tumour).
*Hyaline globules - pale pink globs (that are paler than RBCs) - '''key feature'''.
*[[Proliferative fasciitis]].
*+/-Hemosiderin deposits.
*[[Solitary fibrous tumour]] ([[Hemangiopericytoma]]).
*[[Desmoplastic fibroblastoma]].
*[[Low-grade fibromyxoid sarcoma]].
*Others.


DDx:
=Perivascular tumours=
*Angiosarcoma (have many mitoses).
This grouping includes only two:<ref name=Ref_WMSP602>{{Ref WMSP|602}}</ref>
*[[Glomus tumour]] - both benign and malignant.
*[[Myopericytoma]].


===IHC===
=Vascular lesions=
*CD31 +ve, CD34 +ve, HHV-8 +ve.
{{Main|Vascular lesions}}
Vascular lesions are "too red"; they have too many RBCs.


==Angiosarcoma==
They include:
*Malignant tumour.
*[[Hemangioma]].
*[[Kaposi sarcoma]].
*[[Masson hemangioma]].
*[[Angiosarcoma]]
*[[Epithelioid hemangioendothelioma]].


===Microscopic===
=Skeletal muscle tumours=
Features:
==Rhabdomyoma==
*Very many small capillaries or irregular shape lined with:
{{Main|Rhabdomyoma}}
**Atypical nuclei, pleomorphic nuclei.
*Mitoses.
*Cytoplasmic vacuoles.
**Cells trying to form lumina - embryologic.


==Rhabdomyosarcoma==
==Rhabdomyosarcoma==
*Often abbreviated ''RMS''.
*Abbreviated ''RMS''.
*Most common paediatric sarcoma.
 
*~6% of all childhood cancer.
{{Main|Rhabdomyosarcoma}}
Comes it two main flavours:
*Alveolar rhabdomyosarcoma.
*Embryonal rhabdomyosarcoma.


Histological subdivision:
The histology may be that of a [[small round cell tumour]].
#Alveolar rhabdomyosarcoma.
#*Usually young adults/adolescents.
#*Early mets common.
#Embryonal rhabdomyosarcoma.
#*Usual <10 years old.
#*Typically locally invasive.


Molecular and histologic subdivision:
=Chondro-osseous tumours=
#Translocation-positive alveolar RMS.
{{Main|Chondro-osseous tumours}}
#Translocation-negative alveolar RMS.
#Embryonal RMS.


Notes:
This grouping includes tumours derived from [[cartilage]] and [[bone]].
*Translocation-negative alveolar RMS shares characteristics with ''embryonal RMS''.


===Microscopy===
=Tumours of uncertain differentiation=
Alveolar rhabdomyosarcoma:
==Angiomatoid fibrous histiocytoma==
*Alveolus-like pattern:
{{Main|Angiomatoid fibrous histiocytoma}}
**Fibrous septae lined by tumour cells.
***Space between fibrous sepate may be filled with tumour: ''solid variant of alveolar rhabdomyosarcoma''.
*Eccentric nucleus (???).
*Cytoplasm - dense pink staining on H&E (if well differentiated).
*Usu. nuclear pleomorphism +++.
*Mitoses common.


===Molecular diagnostics===
==Aggressive angiomyxoma==
====Alveolar rhabdomyosarcoma====
*[[AKA]] deep aggressive angiomyxoma.
Common translocations (~80%):
{{Main|Aggressive angiomyxoma}}
*t(1,13).
**PAX3/FKHR fusion gene.
*t(2,13).
**PAX7/FKHR fusion gene.


Several uncommon translocations exist.
==Angiomyofibroblastoma==
{{Main|Angiomyofibroblastoma}}


===IHC===
==Extrarenal malignant rhabdoid tumour==
*Desmin (best marker).
*Essentially identical to ''[[renal malignant rhabdoid tumour]]''.<ref name=Ref_WMSP627>{{Ref WMSP|627}}</ref>
*Actin.
{{Main|Extrarenal malignant rhabdoid tumour}}


==Clear cell sarcoma==
==Ewing sarcoma/PNET==
*Known among pathologists as "soft-tissue melanoma" and "melanoma of the soft parts", as it has a strong morphological resemblance.<ref name=pmid18300804>{{cite journal |author=Hisaoka M, Ishida T, Kuo TT, ''et al.'' |title=Clear cell sarcoma of soft tissue: a clinicopathologic, immunohistochemical, and molecular analysis of 33 cases |journal=Am. J. Surg. Pathol. |volume=32 |issue=3 |pages=452–60 |year=2008 |month=March |pmid=18300804 |doi=10.1097/PAS.0b013e31814b18fb |url=}}</ref>
{{Main|Ewing sarcoma}}
**Molecular changes and origin distinct from melanoma.  
*A [[small round blue cell tumour]] that may be seen in [[bone]]. It is discussed in the context of [[bone tumours]].
*Incidence: rare soft tissue tumour.


===Clinical===
==Epithelioid sarcoma==
*Usually - deep soft tissue ''or'' extremities.
:Sarcomas with an epithelioid morphology are covered in ''[[epithelioid sarcomas]]''.
*Guarded prognosis.
{{Main|Epithelioid sarcoma}}
*First described in 1965.<ref>URL: [http://www.informaworld.com/smpp/723576818-750600/ftinterface~db=all~content=a789166263~fulltext=713240928 http://www.informaworld.com/smpp/723576818-750600/ftinterface~db=all~content=a789166263~fulltext=713240928]. Accessed on: 5 May 2010.</ref>


===Microscopy===
==Alveolar soft part sarcoma==
Features:<ref name=pmid18300804/>
{{Main|Alveolar soft part sarcoma}}
*Architecture: sheets or fascicular (bundles) arrangement.
*Cells: Spindle cells or epithelioid cells.
*Prominent nucleoli - basophilic.
*Fibrous septae.
*Uniform


Image:
==Desmoplastic small round cell tumour==
*[http://commons.wikimedia.org/wiki/File:Clear_cell_sarcoma.Image12.jpg Clear cell sarcoma (WC)].
{{Main|Desmoplastic small round cell tumour}}
*[http://www.informaworld.com/ampp/image?path=/713690780/789166263/sonc_a_284443_o_f0003g.jpeg Clear cell sarcoma (informaworld.com)].


===IHC===
==Clear cell sarcoma==
Features:<ref name=pmid18300804/>
{{Main|Clear cell sarcoma}}
*S100 +ve.
*HMB-45 +ve.
*Melan A (MART-1) +ve; sometimes -ve.
*bcl-2 +ve.
*CD57 +ve (usually).


Keratins:
==Synovial sarcoma==
*EMA may be +ve.
{{Main|Synovial sarcoma}}
*CAM5.2 -ve.
*AE1/AE3 -ve.


===Molecular studies===
=Other=
*Chromosomal translocation t(12;22)(q13;q12).<ref name=pmid18300804/>
==Granulocytic sarcoma==
**Fusion transcripts:  
*Common alternate terms: extramedullary leukemia,<ref name=pmid21795742>{{Cite journal  | last1 = Bakst | first1 = RL. | last2 = Tallman | first2 = MS. | last3 = Douer | first3 = D. | last4 = Yahalom | first4 = J. | title = How I treat extramedullary acute myeloid leukemia. | journal = Blood | volume = 118 | issue = 14 | pages = 3785-93 | month = Oct | year = 2011 | doi = 10.1182/blood-2011-04-347229 | PMID = 21795742 }}</ref> myeloid sarcoma, chloroma.
***EWSR1-ATF1.
*Other terms:<ref name=pmid21556238>{{Cite journal  | last1 = Eom | first1 = KS. | last2 = Kim | first2 = TY. | title = Intraparenchymal myeloid sarcoma and subsequent spinal myeloid sarcoma for acute myeloblastic leukemia. | journal = J Korean Neurosurg Soc | volume = 49 | issue = 3 | pages = 171-4 | month = Mar | year = 2011 | doi = 10.3340/jkns.2011.49.3.171 | PMID = 21556238 | PMC = 3085814 | url = http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3085814/ }}</ref> myeloblastoma, chloromyeloma, chloromyelosarcoma, granulocytic leukosarcoma, or myelosarcoma.
***EWSR1-CREB1 (GI tract associated).
{{Main|Granulocytic sarcoma}}


==See also==
=See also=
*[[Bone]].
*[[Bone]].
*[[Dermatopathology]].
*[[Dermatopathology]].
*[[Hematopathology]].
*[[Hematopathology]].
*[[Spindle cell lesion]].
*[[Spindle cell lesion]].
*[[Neurofibromatosis]].
*[[Small round cell tumours]].


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


[[Category:Weird stuff]]
[[Category:Soft tissue lesions]]
Michael
48,466

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