CS Site-Specific Factor 9

Mitotic Count


**Note 1**: The mitotic count, the number of mitoses per 40 high-power fields (HPF), reflects the potential aggressiveness or prognosis of uveal melanomas. This site-specific factor presumes the denominator of 40 HPF, so just the numerator (the mitotic count) is coded here. For other schemas in which mitotic count is collected, the denominator may vary. **Note 2**: An HPF usually has a magnification objective of 40 (a 40x field). As described in the AJCC chapter on uveal melanomas, the typical field area is 0.15-0.19 square millimeters (mm). **Note 3**: Record mitotic count to the nearest tenth as documented in the pathology report. For example, a mitotic count of 6/40 HPF would be coded 060. **Note 4**: Code the specific mitotic count only per 40 HPF; assume the denominator is 40 HPF if not specified. Use code 996 only if the mitotic count is expressed with a specific denominator other than 40 HPF.




NAACCR #2863


Code Description
000 0 mitoses per 40 high-power fields (HPF) (40x field)
Mitoses absent, no mitoses present, no mitotic activity
001-008 0.1-0.8 mitosis per 40 HPF (40x field)
009 0.9 mitosis per 40 HPF(40x field)

Stated as less than 1 mitosis per 40 HPF (40x field)
010-100 1-10 mitoses per 40 HPF (40x field)
110 11 or more mitoses per 40 HPF (40x field)
988 Not applicable: Information not collected for this case
(If this information is required by your standard setter, use of code 988 may result in an edit error.)
990 Stated as low mitotic count or rate with no specific number
991 Stated as high mitotic count or rate with no specific number
996 Mitotic count described with denominator other than 40 HPF (40x field)
998 No histologic specimen from primary site
999 Unknown or no information
Not documented in patient record