Gastrointestinal stromal tumor (abbreviated as GIST) is a tumor originating from Cajal cells in the gastrointestinal tract; the degree of malignancy varies, and some tumors may or may not progress without treatment , some tumors may not respond well even with treatment. But in general, the smaller the tumor and the fewer mitoses, the better the prognosis; therefore, it is recommended to remove the tumor in time; before the treatment of gastrointestinal stromal tumors, accurate pathological diagnosis of the tumor must be made.
GIST can occur anywhere in the gastrointestinal tract, but is most commonly affectedstomach (55-60%) and small intestine(30-35%), rectal (4%-5%) and duodenum (4 %-5%), with very few cases occurring in the esophagus (<1%), colon and appendix (1%-2%).
- small submucosal or duodenal nodules less than 2 cm, Endoscopic biopsy can be difficult, and laparoscopy/open resection may be the only option for histological diagnosis/treatment; however, in older patients, observation may be a safe option.
- <=2cm GIST, whether located in the stomach or intestine, is currently considered to be of very low risk; Benign tumor; however, close observation and follow-up are still required.
- The standard approach for rectal nodules is biopsy or excision after endorectal ultrasound assessment and pelvic magnetic resonance imaging (MRI), regardless of tumor size and nuclear division. In fact, this site has a higher risk of tumor progression than most gastric GISTs, a significantly worse prognosis and a more critical local impact on surgery;
- < The standard approach for tumors ≥2 cm in span is biopsy/resection. According to the specific situation (large tumor or involving multiple organs, etc.), laparoscopic/open resection, or ultrasound-guided or ultrasound/computed tomography (CT)-guided coarse needle aspiration can be used for pathological diagnosis, so that clinicians can Optimal treatment strategy (appropriate neoadjuvant therapy; avoidance of surgery for diseases not amenable to surgery (eg, lymphoma, mesenteric fibromatosis, and germ cell tumors)) after pathological findings are available.
- If the patient presents with overt metastatic disease, biopsy of the metastases (if easier to perform compared to the primary tumor) is sufficient to confirm the diagnosis and decide on treatment.
- Pathologically, the diagnosis of GIST relies on morphological and immunohistochemical and molecular testing .
1) The immunohistochemical index is often CD117 ( KIT ) and/or DOG1; however, approximately 5% of GISTs are negative for CD117.
2) mitotic counts have prognostic value, and mitotic counts with a total area of 5 mm2 should be counted [approximately equal to 25-25 high-power fields] )area. Patients with more than 5 mitoses have a relatively poor prognosis.
3) Ki-67 predicts the speed of tumor growth to some extent, but the current data cannot support it to replace the mitotic count, and it has not been included in the prognostic system.
4) KIT, PDGFRA , BRAFmutation or NTRK mutation detection and SDHB immunohistochemical detection are currently considered to be closely related to the treatment of patients and to predict the sensitivity of patients to drugs. Therefore, pre-treatment testing is strongly recommended (parenteral GISTs <2 cm can be largely excluded, and these GISTs are unlikely candidates for drug therapy).
In rare cases,BRAFmutations Or NTRKmay find gene rearrangements that may have therapeutic implications.
No KIT/PDGFRAmutations were detected In the GIST of , SDH complex subunit B (SDHB) immunohistochemistry was performed to identify SDH-deficient GIST.
Quad-negative GIST (for KIT/PDGFRs/BRAF/SDH), an underlying NF1 syndrome should be excluded first.
References:
Gastrointestinal stromal tumors: ESMO–EURACAN–GENTURIS diagnosis, treatment and Follow-up Clinical Practice Guidelines.DOI:https://doi.org/10.1016/j.annonc.2021.09.005
CSCO2021 Guidelines for the diagnosis and treatment of gastrointestinal stromal tumors.