Table 7.
MSI Status, MMR-IHC, and Sensitivity and Specificity of Each Mononucleotide Marker in Detecting MMR Status
| MSI status | IHC | Marker
|
|||||||
|---|---|---|---|---|---|---|---|---|---|
| BAT-25 | BAT-26 | BAT-40 | NR-21 | NR-22 | NR-24 | D5S346 | D17S250 | ||
| MSS | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 23 | 23 |
| MSI-L | 28 | 18 | 17 | 23 | 27 | 28 | 28 | 26 | 26 |
| Total IHC+ | 53 | 43 | 42 | 48 | 52 | 53 | 53 | 49 | 44 |
| Specificity (%) | 81 | 79 | 91 | 98 | 100 | 100 | 92 | 83 | |
| Total MSI-H/IHC− | 6 | 6 | 6 | 6 | 4 | 5 | 3 | 2 | 3 |
| Sensitivity (%) | 100 | 100 | 100 | 67 | 83 | 50 | 33 | 50 | |
Fifty-nine of 61 cases were included for specificity and sensitivity calculations. Two cases were excluded because of equivocal IHC staining. Fifty-three of 59 IHC eligible cases were intact for all three mismatch repair proteins, and 6 of 59 demonstrated loss of at least one of three mismatch repair proteins. IHC+, mismatch repair protein immunohistochemistry intact, all MMR proteins (hMLH1, hMSH2, and hMSH6) are expressed in tumor and normal cell nuclei; MSI-H/IHC−, multiple loci unstable in at least three loci/immunohistochemistry negative in at least one of the MMR proteins and demonstrate a decrease or loss (at least 90%) of protein expression in tumor nuclei.