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Small bowel (small intestine)

Other malignancies

Staging-GIST

Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 22 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Staging system also used for GIST of esophagus, colorectum, mesentery and peritoneum

Primary tumor (T)
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TX: Primary tumor cannot be assessed
T0: No evidence for primary tumor
T1: Tumor 2 cm or less
T2: Tumor more than 2 cm but not more than 5 cm
T3: Tumor more than 5 cm but not more than 10 cm
T4: Tumor more than 10 cm in greatest dimension

● For ruptured tumors, use radiologic data to estimate tumor size

Regional lymph nodes (N)
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N0: No regional lymph node metastasis
N1: Regional lymph node metastasis

● Nodal metastases are extremely rare in GIST, so there is no routine indication for lymph node biopsy or lymph node dissection
● Use N0/pN0 if no information on nodal status; do not use NX

Distant Metastasis (M)
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M0: No distant metastasis
M1: Distant metastasis (specify site, if known)

● Most GISTs metastasize to intra-abdominal soft tissue or liver
● Intra-abdominal metastasis refers to tumor involvement in abdominal cavity away from the primary mass, usually to serosal surfaces of abdomen, pelvis, retroperitoneum
● Multiple primary tumors are associated with neurofibromatosis type 1 or familial GIST syndrome and should not be considered intraabdominal metastasis, although rare cases of multiple independent GISTs at different GI locations have been reported
● If no primary GI GIST is identified, solitary omental, mesenteric, pelvic or retroperitoneal GISTs should be considered primary tumors
● A liver metastasis implies metastatic tumor inside the liver parenchyma as 1 or more nodules, but adherence to liver capsule, even if extensive, should not be considered liver metastasis

Anatomic stage / prognostic groups
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Stage IA: T1-2 N0 M0 and low mitotic rate
Stage IB: T3 N0 M0 and low mitotic rate
Stage II: T1-2 N0 M0 and high mitotic rate or T4 N0 M0 and low mitotic rate
Stage IIIA: T1 N0 M0 and high mitotic rate OR T4 N0 M0 and low mitotic rate
Stage IIIB: T2-4 N0 M0 and high mitotic rate
Stage IV: N1 or M1

● Low mitotic rate: 5 or fewer per 50 HPF
● High mitotic rate: over 5 per 50 HPF
● The required total count of mitoses is per 5 mm² on the glass slide (50 HPF for older microscopes, 20 HPF for newer microscopes)

Tables
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Guidelines for risk assessment of primary gastrointestinal stromal tumor

Additional references
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● Protocol for the Examination of Specimens From Patients With GIST (pdf)

End of Small bowel (small intestine) > Other malignancies > Staging-GIST

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