<aside> 📘 Gastrointestinal stromal tumours: ESMO EURACAN GENTURIS Clinical Practice Guidelines for diagnosis, treatment and follow-up. 2021

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Flowcharts

Management of local/locoregional disease
Management of advanced/metastatic disease

Etiology of GIST

Arise from the interstitial cells of Cajal (ICC) or their precursors, which are specialized cells that regulate the motility of the gastrointestinal tract.

Epidemiology

Rare tumors with significant variations in reported incidence, ranging from 0.4 to 2 cases per 100,000 per year
There is a slightly higher incidence of GIST in males, and the median age is around 60-65 years, with a wide range

Molcular biology

Gene	Explanation
CD117 (KIT)	tyrosine kinase that is expressed in approximately 95% of GISTs.
DOG1	A more sensitive and specific marker that is expressed in approximately 98% of GISTs.
PDGFRs	Generally less aggressive than those with KIT mutations . Imatinib, a tyrosine kinase inhibitor, is effective in treating GISTs with PDGFR mutations
SDH complex subunit B (SDHB)	IHC for SDHB is carried out to identify SDH-deficient GIST. SDH-deficient GISTs are more commonly found in the stomach and are associated with a higher risk of malignancy and metastasis.
BRAF	Less than 5% of cases. Benefit from BRAF inhibitors (including BRAFeMEK inhibitor combinations)
Quadruple-negative GIST (for KIT/PDGFRs/BRAF/SDH)	An unrecognized underlying NF1 syndrome should be excluded. It is recommended to avoid imatinib or any adjuvant treatment in NF1-related GISTs

Approach lesion

Diagnosis method

Category of Lesion	Standard Method
Esophagogastric or duodenal nodules <2 cm	Endoscopic ultrasound (EUS)
Large mass likely requiring multivisceral resection	Multiple core needle biopsies through EUS guidance or ultrasound/CT-guided percutaneous approach

Principle of management

Size	Biopsy Feasibility	Corresponding Management
< 2 cm	Yes	Resection should be performed if diagnosis of GIST is made, unless major morbidity is expected (esophagogastric junction, second portion of the duodenum on the medial aspect).
	No	Could be monitored with imaging studies (such as CT scans or MRI) to assess the size and growth of the tumor over time. 3 months is a logical interval.
≥ 2 cm	Yes	The standard approach is to perform biopsy or excision.
	No	Laparoscopic/open surgery is recommended if there is an abdominal nodule or a mobile mass in the abdominal cavity not amenable to endoscopic assessment.
Rectal nodules	Yes	The standard approach to rectal nodules is represented by biopsy or excision after endorectal ultrasound assessment and MRI, regardless of the tumor size and mitotic rate. The prognosis of rectal GIST is generally worse than that of gastric GIST, and the local implications for surgery are more critical.