**4. Gastric gastrointestinal stromal tumours (GISTs)**

GISTs are mesenchymal tumours that develop from the interstitial cells of Cajal (gastrointestinal pacemakers) anywhere in the GI tract. GISTs are rare constituting only less than 1% of all GI malignancies. Although the annual reported incidence is just 10 cases per million, the actual Incidence is believed to be much higher [22]. The stomach is the most common location for GISTs (70%). The driving force for GIST development is a gain-of-function mutation in tyrosine kinase receptor gene *c-KIT* [21].

Although the discovery of tyrosine kinase inhibitor imatinib has been the most significant change in GIST treatment over recent years, surgery as the only potentially curative method remains the cornerstone of treatment [23].

Gastric GISTs start their growth in deeper layers, mostly in the smooth muscle layer of gastric wall; expand intra- or extraluminally and eventually produce haematogenous metastasis in solid organs or peritoneum. They can also cause sarcomatosis by perforating into peritoneal cavity [21].

Any patient who is medically fit should undergo complete surgical resection of gastric GIST. However, NCCN and ESMO guidelines recommend endoscopic surveillance for small (<1 cm and <2 cm, respectively) gastric lesions if high-risk features are not present by endoscopic ultrasound investigation (ulcerations (see **Figure 11**), cystic spaces, irregular borders, echogenic foci and heterogeneity). All other cases and patients who do not want to undergo endoscopic surveillance should be treated by surgical resection [21, 24].

Unlike for carcinoma, a wide resection margin of healthy tissue is not necessary for GISTs. It is of paramount importance to be meticulous and remove the entire lesion without damaging tumour pseudocapsule or causing tumour spillage or bleeding as this would increase the risk of locoregional recurrence and sarcomatosis. GISTs rarely spread via lymphatics; therefore, lymphadenectomy is not necessary. If noted, enlarged lymph nodes near the tumour can selectively be dissected. Either wedge resection or full-thickness partial gastrectomy is usually sufficient for lesser and greater curvature tumours, whereas a transgastric resection after anterior gastrotomy incision is performed for posterior wall gastric GISTs. Total or subtotal gastrectomy is only required for tumours occupying large portions of the stomach. If the tumour is borderline resectable or a extensive operation

**Figure 11.** Gastrointestinal stromal tumour. Note the umbilicated ulceration.

(total gastrectomy, en bloc resection of adjacent organs) is predicted, neoadjuvant treatment with imatinib is used to downstage the tumour and perform less extensive surgery in advanced cases [21–24].

Laparoscopic surgery is considered a feasible and safe option for the treatment of small (<5 cm) gastric GISTs as long as the general oncologic principles are followed. This statement is supported by evidence from several retrospective cohort studies [23]. Direct manipulation of the tumour with instruments is contraindicated, and a plastic bag must be used on extraction to reduce the risk of spillage. Both ESMO and NCCN guidelines support the use of laparoscopic technique for small gastric GISTs (<5 cm) [23]. Although there are studies that indicate feasibility for larger tumours [25], more high-quality research is needed to widen this indication. A hybrid procedure, endoscopy-assisted laparoscopic resection, can aid in tumour localisation and preservation of gastric volume. While it is currently performed in a limited amount of centres, it will probably take a more prominent place amongst minimally invasive gastric procedures [21].
