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| LMDDx = [[schwannoma]], [[leiomyoma]], [[leiomyosarcoma]], [[neurofibroma]], [[desmoid-type fibromatosis]] | | LMDDx = [[schwannoma]], [[leiomyoma]], [[leiomyosarcoma]], [[neurofibroma]], [[desmoid-type fibromatosis]] | ||
| Stains = | | Stains = | ||
| IHC = CD117 +ve, | | IHC = CD117 +ve, [[DOG1]] +ve, CD34 +ve, S-100 -ve | ||
| EM = | | EM = | ||
| Molecular = mutation in KIT gene ''or'' PDGFRA gene | | Molecular = mutation in KIT gene ''or'' PDGFRA gene | ||
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===Definition=== | ===Definition=== | ||
*Tumour resulting from a mutation in the KIT gene ''or'' PDGFRA (Platelet-derived growth factor receptor, alpha polypeptide) gene.<ref name=pmid17090188/> | *Tumour resulting from a mutation in the KIT gene ''or'' PDGFRA (Platelet-derived growth factor receptor, alpha polypeptide) gene.<ref name=pmid17090188/> | ||
*Cases wild-type for KIT or PDFGRA may harbour defects in the [[succinate dehydrogenase]] complex, NF-1, BRAF, or extremely rarely KRAS. | |||
===Epidemiology=== | ===Epidemiology=== | ||
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*Large size. | *Large size. | ||
**Often benign if small size. | **Often benign if small size. | ||
*High mitotic rate (for area 5mm | *High mitotic rate (for area 5mm<sup>2</sup>). | ||
*Site - small intestine GISTs worse than stomach GISTs. | *Site - small intestine GISTs worse than stomach GISTs. | ||
Small intestine bad prognosis:<ref name=pmid17090188/> | Small intestine bad prognosis:<ref name=pmid17090188/> | ||
* >5 mitoses/5 mm | * >5 mitoses/5 mm<sup>2</sup> ''or'' size >10 cm. | ||
Stomach bad prognosis:<ref name=pmid17090188/> | Stomach bad prognosis:<ref name=pmid17090188/> | ||
* >5 mitoses/5 mm | * >5 mitoses/5 mm<sup>2</sup> ''and'' size >5 cm. | ||
===Location=== | ===Location=== | ||
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Notes: | Notes: | ||
*Small intestinal GISTs have a worse prognosis than gastric ones.<ref name=pmid17090188/> | *Small intestinal GISTs have a worse prognosis than gastric ones.<ref name=pmid17090188/> | ||
*GISTs almost never metastasize to the [[lymph node]]s | *GISTs almost never metastasize to the [[lymph node]]s (except for SDH-B deficient epithelioid GISTs) | ||
**Most common [[metastasis]] locations: [[liver]], abdominal soft tissue. | **Most common [[metastasis]] locations: [[liver]], abdominal soft tissue. | ||
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** May be epithelioid (round) ~40% of tumours. | ** May be epithelioid (round) ~40% of tumours. | ||
** Mixed epithelioid and spindle cell tumours ~10% tumours. | ** Mixed epithelioid and spindle cell tumours ~10% tumours. | ||
*+/-Cytoplasmic inclusions | *+/-Cytoplasmic inclusions<ref name=pmid7757951>{{cite journal |author=Pasquinelli G, Severi B, Martinelli GN, Santini D, Gelli MC, Tison V |title=Gastro-intestinal stromal tumors: an ultrastructural reinterpretation of the clear cell component |journal=J. Submicrosc. Cytol. Pathol. |volume=27 |issue=2 |pages=251–7 |year=1995 |month=April |pmid=7757951 |doi= |url=}}</ref> - perinuclear.<ref>{{Cite journal | last1 = Boşoteanu | first1 = M. | last2 = Boşoteanu | first2 = C. | last3 = Deacu | first3 = M. | last4 = Aşchie | first4 = M. | title = Differential diagnosis of a gastric stromal tumor: case report and literature review. | journal = Rom J Morphol Embryol | volume = 52 | issue = 4 | pages = 1361-8 | month = | year = 2011 | doi = | PMID = 22203947 }}</ref> | ||
*Classically splits the layers of the ''muscularis propria'' - as this is where the ''interstitial cells of Cajal'' are located.<ref name=pmid16402273>{{cite journal |author=Agaimy A, Wünsch PH |title=Gastrointestinal stromal tumours: a regular origin in the muscularis propria, but an extremely diverse gross presentation. A review of 200 cases to critically re-evaluate the concept of so-called extra-gastrointestinal stromal tumours |journal=Langenbecks Arch Surg |volume=391 |issue=4 |pages=322–9 |year=2006 |month=August |pmid=16402273 |doi=10.1007/s00423-005-0005-5 |url=}}</ref> | *Classically splits the layers of the ''muscularis propria'' - as this is where the ''interstitial cells of Cajal'' are located.<ref name=pmid16402273>{{cite journal |author=Agaimy A, Wünsch PH |title=Gastrointestinal stromal tumours: a regular origin in the muscularis propria, but an extremely diverse gross presentation. A review of 200 cases to critically re-evaluate the concept of so-called extra-gastrointestinal stromal tumours |journal=Langenbecks Arch Surg |volume=391 |issue=4 |pages=322–9 |year=2006 |month=August |pmid=16402273 |doi=10.1007/s00423-005-0005-5 |url=}}</ref> | ||
*+/-Skenoid fibres - extracellular collagen bundles<ref name=pmid15798063/> ~ 2-5 x 60 micrometers - uncommon finding. | *+/-Skenoid fibres - extracellular collagen bundles<ref name=pmid15798063/> ~ 2-5 x 60 micrometers - uncommon finding. | ||
**Not seen in gastric GISTs.<ref name=pmid12692202/> | **Not seen in gastric GISTs.<ref name=pmid12692202/> | ||
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*CD117 +ve in 95%.<ref name=pmid17090188/> | *CD117 +ve in 95%.<ref name=pmid17090188/> | ||
**[[Mast cell]]s are the internal positive control. | **[[Mast cell]]s are the internal positive control. | ||
*DOG1 +ve.<ref name=pmid19011564>{{Cite journal | last1 = Liegl | first1 = B. | last2 = Hornick | first2 = JL. | last3 = Corless | first3 = CL. | last4 = Fletcher | first4 = CD. | title = Monoclonal antibody DOG1.1 shows higher sensitivity than KIT in the diagnosis of gastrointestinal stromal tumors, including unusual subtypes. | journal = Am J Surg Pathol | volume = 33 | issue = 3 | pages = 437-46 | month = Mar | year = 2009 | doi = 10.1097/PAS.0b013e318186b158 | PMID = 19011564 }}</ref> | *[[DOG1]] +ve.<ref name=pmid19011564>{{Cite journal | last1 = Liegl | first1 = B. | last2 = Hornick | first2 = JL. | last3 = Corless | first3 = CL. | last4 = Fletcher | first4 = CD. | title = Monoclonal antibody DOG1.1 shows higher sensitivity than KIT in the diagnosis of gastrointestinal stromal tumors, including unusual subtypes. | journal = Am J Surg Pathol | volume = 33 | issue = 3 | pages = 437-46 | month = Mar | year = 2009 | doi = 10.1097/PAS.0b013e318186b158 | PMID = 19011564 }}</ref> | ||
Others: | Others: | ||
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NEGATIVE: Desmin, S-100. | NEGATIVE: Desmin, S-100. | ||
PROLIFERATION (Ki-67): <1%. | PROLIFERATION (Ki-67): <1%. | ||
</pre> | |||
====Incidental GIST==== | |||
<pre> | |||
Partial Stomach, Sleeve Gastrectomy: | |||
- Stomach wall with incidental GASTROINTESTINAL STROMAL TUMOUR (GIST), 2 mm in maximal dimension. | |||
-- Margin clear. | |||
- Gastric mucosa within normal limits. | |||
Comment: | |||
The tumour stains as follows: | |||
POSITIVE: DOG1, CD117, CD34. | |||
NEGATIVE: desmin, S-100. | |||
PROLIFERATION (Ki-67): <2%. | |||
</pre> | </pre> | ||
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