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===Microscopic=== | ===Microscopic=== | ||
Features: | Features: | ||
*Smooth muscle differentiation - ''' | *Smooth muscle differentiation - '''essential'''. | ||
**Fascicular architecture. | **Fascicular architecture. | ||
***Whorled look at low power. | ***Whorled look at low power. | ||
***Groups of spindle cells cut peripendicular to their long axis adjacent to groups of spindle cells cut in the plane of their long axis. | ***Groups of spindle cells cut peripendicular to their long axis adjacent to groups of spindle cells cut in the plane of their long axis. | ||
**May rely on [[IHC]] - if poorly differentiated. | **May rely on [[IHC]] - if poorly differentiated. | ||
*Malignant histomorphologic features - | *Malignant histomorphologic features - two of three required - '''key features''':<ref name=pmid21865091>{{Cite journal | last1 = Ip | first1 = PP. | last2 = Cheung | first2 = AN. | title = Pathology of uterine leiomyosarcomas and smooth muscle tumours of uncertain malignant potential. | journal = Best Pract Res Clin Obstet Gynaecol | volume = 25 | issue = 6 | pages = 691-704 | month = Dec | year = 2011 | doi = 10.1016/j.bpobgyn.2011.07.003 | PMID = 21865091 }}</ref> | ||
*#[[Nuclear pleomorphism]]. | *#[[Nuclear pleomorphism]]. | ||
*#[[ | *#Coagulative tumour cell [[necrosis]] | ||
*#*Should be patchy/multifocal. | *#*Should be patchy/multifocal. | ||
*#*Zonal necrosis is suggestive of vascular cause and may be a degenerative change. | *#*Zonal necrosis is suggestive of vascular cause and may be a degenerative change. | ||
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*#*5 mitoses/HPF - if epithelioid. | *#*5 mitoses/HPF - if epithelioid. | ||
*#*2 mitoses/HPF - if [[myxoid]]. | *#*2 mitoses/HPF - if [[myxoid]]. | ||
Note: | |||
*The mitotic rate seems to be a relatively weak predictor; a modest rate may be malignant and a high rate benign.<ref name=pmid9388868>{{Cite journal | last1 = Guo | first1 = L. | last2 = Liu | first2 = T. | last3 = Huang | first3 = H. | title = [Reappraisal of the pathological criteria for uterine leiomyosarcoma]. | journal = Zhonghua Bing Li Xue Za Zhi | volume = 25 | issue = 5 | pages = 266-9 | month = Oct | year = 1996 | doi = | PMID = 9388868 }}</ref> | |||
DDx: | DDx: | ||
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*[[Undifferentiated endometrial sarcoma]]. | *[[Undifferentiated endometrial sarcoma]]. | ||
*[[Smooth muscle tumour of uncertain malignant potential]]. | *[[Smooth muscle tumour of uncertain malignant potential]]. | ||
*[[Uterine leiomyoma]]. | |||
===IHC=== | ===IHC=== |
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