TNM Classification, Histologic Grade, Prognostic Stage, and Risk Stratification
The American Joint Committee on Cancer tumor/node/metastasis (TNM) classification for gastrointestinal stromal tumors (GISTs) is provided below, along with anatomic stage/prognostic groups. [1]
Table 1. TNM classification of gastrointestinal stromal tumors (Open Table in a new window)
Primary tumor (T) |
|
TX |
Primary tumor cannot be assessed |
T0 |
No evidence of primary tumor |
T1 |
Tumor ≤ 2 cm |
T2 |
Tumor > 2 cm but ≤ 5 cm |
T3 |
Tumor > 5 cm but ≤ 10 cm |
T4 |
Tumor > 10 cm in greatest dimension |
Regional lymph nodes (N) |
|
N0 |
No regional lymph node metastasis |
N1 |
Regional lymph node metastasis |
Distant metastasis (M) |
|
M0 |
No distant metastasis |
M1 |
Distant metastasis |
Table 2. Histologic grade (Open Table in a new window)
Histologic grade (G) |
|
GX |
Grade cannot be assessed |
G1 |
Low grade; mitotic rate 5/50 per high-power field (HPF) or less |
G2 |
High grade; mitotic rate > 5/50 HPF |
Table 3. Anatomic stage/prognostic groups for gastric and omental GISTs (Open Table in a new window)
Stage |
T |
N |
M |
Mitotic rate |
IA |
T1 or T2 |
N0 |
M0 |
Low mitotic rate |
IB |
T3 |
N0 |
M0 |
Low mitotic rate |
II |
T1 |
N0 |
M0 |
High mitotic rate |
T2 |
N0 |
M0 |
High mitotic rate |
|
T4 |
N0 |
M0 |
Low mitotic rate |
|
IIIA |
T3 |
N0 |
M0 |
High mitotic rate |
IIIB |
T4 |
N0 |
M0 |
High mitotic rate |
IV |
Any T |
N1 |
M0 |
Any rate |
Any T |
Any N |
M1 |
Any rate |
Table 4. Anatomic stage/prognostic groups for small intestinal, esophageal, colorectal, mesentric, and peritoneal GISTs (Open Table in a new window)
Stage |
T |
N |
M |
Mitotic rate |
I |
T1 or T2 |
N0 |
M0 |
Low mitotic rate |
II |
T3 |
N0 |
M0 |
Low mitotic rate |
IIIA |
T1 |
N0 |
M0 |
High mitotic rate |
T4 |
N0 |
M0 |
Low mitotic rate |
|
IIIB |
T2 |
N0 |
M0 |
High mitotic rate |
T3 |
N0 |
M0 |
High mitotic rate |
|
T4 |
N0 |
M0 |
High mitotic rate |
|
IV |
Any T |
N1 |
M0 |
Any rate |
Any T |
Any N |
M1 |
Any rate |
The decision whether to pursue adjuvant treatment depends on an estimation of risk of recurrence, which is typically based on the following factors [2, 3] :
-
Tumor size
-
Mitotic index
-
Location within the GI tract
-
Presence or absence of tumor rupture
Yang et al reported that the mitotic index in GISTs can be reliably predicted with the use of a magnetic resonance imagimg texture-based model. [4]
Table 5. Modified National Institutes of Health risk stratification criteria for GIST (Open Table in a new window)
Risk category | Tumor size (cm) | Mitotic index (per 50 HPFs) | Primary tumor site |
---|---|---|---|
Very low risk | < 2.0 | ≤ 5 | Any |
Low risk | 2.1 to 5.0 | ≤ 5 | Any |
Intermediate risk | 2.1 to 5.0 | > 5 | Gastric |
< 5.0 | 6 to 10 | Any | |
5.1 to 10.0 | ≤ 5 | Gastric | |
High Risk | Any | Any | Any, with tumor rupture |
> 10 | Any | Any | |
Any | > 10 | Any | |
> 5 | > 5 | Any | |
2.1 to 5.0 | > 5 | Nongastric | |
5.1 to 10.0 | ≤ 5 | Nongastric |