Why MSI Status Now Drives Treatment Decisions
Endometrial cancer has four molecular subtypes. MSI-H/dMMR (high microsatellite instability or deficient mismatch repair) is the most important one for clinic teams. It determines who gets immunotherapy, shapes treatment choices after surgery, and signals the need for Lynch syndrome testing. Getting the right result, storing it where doctors can find it, and using it quickly all matter.
Studies show the MSI-H rate in endometrial cancer at about 25.7% - roughly one in four patients. For a clinic seeing 200 endometrial cancer cases yearly, about 50 patients have treatment choices that depend on this one result. When testing itself is fragmented, problems multiply.
Three Testing Methods, Three Operational Profiles
Labs use three main ways to test MSI and MMR status: immunohistochemistry, polymerase chain reaction, and next-generation sequencing. Each has different timing and different problems that can happen.
- Immunohistochemistry (IHC). Available everywhere, fast results, looks for missing MMR protein in tissue samples. Needs excellent specimen handling and a skilled pathologist to read. Small or poorly prepared samples can give wrong answers - the quality of slide prep matters a lot.
- PCR-based panels. Detect instability in specific DNA regions. Standard panels take at least three working days in the lab. How well they work depends on which regions the panel checks and how many regions it uses.
- Next-generation sequencing (NGS). Checks instability across more of the genome and finds other molecular information at the same time. Takes about seven working days of lab work and analysis. This longer wait slows down when treatment decisions can be made.
A 2025 best practice document from the European Molecular Genetics Quality Network says no single method works best everywhere. Each requires specific sample prep and each has limits clinics must manage both technically and operationally. Full technical details are in the EMQN guidelines for MSI analysis in solid tumours.
Where Clinic Workflows Break Down
MSI testing complexity creates known problems. Guidelines say all endometrial cancer cases should get MSI/MMR testing, but clinics do this differently. They use different methods, file results different ways, and some don't review findings before starting treatment.
Four breakdown patterns show up repeatedly in endometrial cancer clinics:
- Results buried in documents. Pathology reports arrive as PDFs. The MSI or MMR result hides in paragraphs of text. When a doctor reviews the patient chart, they won't see it without opening the full report and reading it word by word.
- No automatic flag on a positive result. When an MSI-H finding comes back, most software does nothing - no alert, no message to follow the clinic's protocol, no task to refer the patient. The result sits in a folder until someone thinks to look for it.
- Method changes go unlinked. When a patient gets IHC testing at biopsy and NGS testing at surgery, results sit in separate places with no link between them. If the tests give different answers, the difference can get missed until someone reviews the chart later.
- Coordination is manual and broken up. According to an American Society for Clinical Pathology report, many labs don't have staff dedicated to coordinating biomarker testing, which causes delays. Oncologists, pathologists, and genetic counselors work in separate channels with no shared task list.
A quality audit of endometrial cancer biopsies found that before changes were made, 15.5% of cases were missing required IHC results, including MMR status. After adding a standardized report form, all 39 cases in a row had the right results. The problem was how reports were written, not how labs worked.
What Structured Data Capture Changes
MSI results matter to clinical decisions, but most software just attaches the lab report as a PDF. When the report arrives, the MSI result stays hidden - the system can't search for it or trigger alerts. Structured data capture takes the text result and converts it into a searchable field the system can use right away.
Tools that do structured data capture pull key molecular findings - like MSI status and MMR marker expression - out of PDFs and convert them into searchable fields in the patient record. A doctor opening a chart sees MSI status in the summary, not buried in an attached report. The system keeps track of where the result came from, when it was extracted, and which test was used. This creates a record that shows how the result got into the chart and helps with compliance review.
See how structured data capture changes daily work.
Flagging, Timelines, and Referral Triggers
Structured capture is the foundation. The next step is rules that act on what was found.
When a system records an MSI-H or dMMR result, it shows a prompt on the doctor's screen. This doesn't tell them what treatment to give. It alerts them that this finding is present and that their clinic's protocol may call for specific next steps - like a genetics referral, a treatment review, or a team meeting.
A timeline shows all molecular results in order, along with scans, labs, and appointments. If a patient got IHC at biopsy and NGS at surgery, both results show in sequence. If they give different answers, that difference shows right away. The doctor doesn't have to switch between two attached PDFs to see it.
MSI-H endometrial cancer links closely to Lynch syndrome. When MSI-H is confirmed, most clinics refer patients for genetic counseling. Automated systems can create this referral task when the result is recorded, so it doesn't get missed. See genetic data security in ovarian cancer clinics for how hereditary cancer results and data safety connect.
Applying the Same Logic Across Biomarker Types
MSI is not the only biomarker creating coordination problems in endometrial and other solid tumor clinics. The same problem - results arriving as documents, no searchable field, no automatic follow-up - happens wherever molecular testing is standard care. HER2 testing in gastric cancer follows the same pattern: a test is ordered, a result arrives as a PDF, and a doctor must manually pull out the result and link it to a treatment choice. See HER2 testing gaps in advanced gastric cancer clinics for how this gap forms and grows.
The same structured extraction and flagging approach works for MSI, MMR, HER2, BRCA, EGFR, and other biomarkers. One extraction tool, one data model, one alert system - set up once, used for all markers a clinic needs. Adding a new biomarker doesn't require building a separate system.
Audit Trails in Molecular Testing
Molecular results affect major decisions about treatment. When a result is used to justify a treatment choice, the team needs a record of when it arrived, who reviewed it, and which version was the final one.
A good system keeps a complete, unchangeable record of every lab result - when it arrived, when it was converted to structured data, and if the report was later updated. Clinical leaders and compliance reviewers can see this record without asking IT. For clinics with strict data rules, this clear record is required. Each entry has a timestamp and shows who made it, so it's clear when information entered the patient record.
Implementing structured data capture for biomarkers requires work. You need to configure MSI and MMR extraction, set flagging rules, and integrate everything into your clinic's workflow. Book a demo to see how this works end to end.