Parameters:
(1) size in centimeters based upon the single largest dimension
(2) mitotic count (I assume this is performed in the most mitotically active areas, although the need to count 50 high powered fields may make this a somewhat mute point)
|
Diameter in cm
|
Mitotic Count per 50 high power fields (HPF)
|
Risk Group
|
|
< 2 cm
|
<= 5
|
very low risk
|
|
2 – 5
|
<= 5
|
low risk
|
|
< 5
|
6 – 10
|
intermediate risk
|
|
5 – 10
|
<= 5
|
intermediate risk
|
|
>= 5 (5 – 10)
|
> 5 (6 – 10)
|
high risk
|
|
> 10
|
any
|
high risk
|
|
any
|
> 10
|
high risk
|
where:
• For very low risk, low risk and intermediate groups, the original table had mitotic rate as "< 5". No assignment was given for "=5". Based on the other table entries "<= 5" seemed appropriate.
• The mitotic rate for high risk is "> 5" in the original table, but "=5" is not assigned for that mitotic count, so ">= 5" seemed appropriate.
• In the footnote to the table it is indicated that small bowel tumors may show more aggressive behavior relative to maximum diameter and that for these tumors the breakpoints for size should be decreased by 1-2 cm.
• The mitotic count and high power field should be standardized.
Limitations:
• The diameter of a tumor may vary relative to fresh, post-fixed or processed states.
• Mitotic counts may vary considerably between observers.
• Occasionally even tumors classified as very low risk may metastasize.
