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Version 25
Data Item #3890: Microsatellite Instability (MSI)

* indicates required field

Length: 1
Source of Standard: NAACCR
Section Name: Stage/Prognostic Factors
Year Implemented: 2018
Version Implemented: 18
Record Types: A, M, C, I

XML NAACCR ID: microsatelliteInstability

Parent XML Element: Tumor

Required Status:

NPCR Collect: RS* - Required, site specific; when available
CoC Collect: RS - Required, site specific
SEER Collect: RS - Required, site specific
CCCR Collect: RS* - Required, site specific; when available

Description:

Microsatellite Instability (MSI) is a form of genetic instability manifested by changes in the length of repeated single- to six-nucleotide sequences (known as DNA microsatellite sequences). High MSI, found in about 15% of colorectal carcinomas, is an adverse prognostic factor for colorectal carcinomas and predicts poor response to 5-FU chemotherapy (although the addition of oxaliplatin in FOLFOX regimens negates the adverse effects [page 266 AJCC manual]). High MSI is a hallmark of hereditary nonpolyposis colorectal carcinoma, also known as Lynch syndrome.

Rationale:

Microsatellite Instability (MSI) is a Registry Data Collection Variable in AJCC. It was previously collected as Colon and Rectum, CS SSF# 7.

Item Data Type:

digits

Allowable Values

0-2, 8, 9

Codes:

0

Microsatellite instability (MSI) stable; microsatellite stable (MSS); negative, NOS
AND/OR
Mismatch repair (MMR) intact, no loss of nuclear expression of MMR proteins
MMR proficient (pMMR or MMR-P)

1

MSI unstable low (MSI-L)

2

MSI unstable high (MSI-H)
AND/OR
MMR deficient (dMMR or MMR-D), loss of nuclear expression of one or more MMR proteins

8

Not applicable: Information not collected for this case
(If this information is required by your standard setter, use of code 8 may result in an edit error.)

9

Not documented in medical record
MSI-indeterminate
MSI-equivocal
Microsatellite instability not assessed or unknown if assessed

Code Notes:

Each Site-Specific Data Item (SSDI) applies only to selected primary sites, histologies, and years of diagnosis. Depending on applicability and standard-setter requirements, SSDIs may be left blank.