**6. Prognosis**

Various risk stratification models (**Table 1**) have been proposed that are based on site, size, mitotic index, and tumor rupture. Gastric GISTs are known to have better prognosis than non-gastric GIST [46].

Tumor rupture is known to be associated with a very high risk of GIST recurrence [47]. TNM staging is also available for GIST staging [48]. However, these stratification systems are not commonly used in clinical practice.

had 45 GIST cases, of which 37 were in the stomach. All GIST patients had R0 resection. There were seven recurrences with five recurrences being gastric GIST recurrences. Thirteen GIST

**Risk definition Risk groups Comments**

Very low risk Low risk Intermediate risk High risk

Low risk Intermediate risk High risk

Low risk Intermediate risk High risk

Risk of recurrence Very low risk

Risk of recurrence Very low risk

Does not differentiate between malignant and benign tumors knowing the fact that even small-size tumors with a low mitotic count may metastasize Does not take GIST site into

http://dx.doi.org/10.5772/intechopen.77297

Gastric GIST

73

Tumor location outside the stomach is a prognostic factor for survival independent of the mitotic count and

This classification considered a total area

HPF characterized by the use of different optical components, while in practice, 50 HPF typically corresponds to a total area

This classification is recommended by

in 50 fields

consideration

tumor size

of 5 mm<sup>2</sup>

of 10 mm2

GEIS guidelines

A computed tomography (CT) scan (**Figure 1a** and **b**) is considered the first imaging to be done to evaluate anatomic location, extension, and metastasis of GISTs. Oral and IV contrast should be given to delineate bowel margins. GISTs can display endophytic and exophytic growth, and large GISTs may appear heterogeneous due to focal areas of hemorrhage or necrosis [53]. Magnetic resonance imaging (MRI) is used to further evaluate liver metastasis or rectal GIST [54]. Fluorodeoxyglucose-positron emission tomography (FDG-PET) is highly sensitive but not specific for GIST, and it is mainly useful to monitor response to tyrosine kinase inhibitors [55, 56]. Upper GI endoscopy may be useful for gastric GIST. Both GISTs and leiomyomas will appear as a submucosal mass with normal overlying mucosa and bulging into gastric lumen. Mucosal ulceration may occur. Endoscopic ultrasound (**Figure 2**) may not be useful, however, when combined with FNA sensitivity, and accuracy may reach 82 and 86%, respectively [57]. Routine biopsy is not needed routinely for local resectable gastric GISTs proved by imaging studies.

patients were Pfetin negative and 5/13 Pfetin negative GISTs had recurrences [52].

**7. Diagnostic evaluation**

**Classification system**

Modified NIH

[45]

NIH [6] Tumor size

AFIP [46] Tumor size

**Prognostic criteria**

Mitotic index

Tumor size Mitotic index Primary tumor site Tumor rupture

Mitotic index location

**Table 1.** Different stratification systems for GISTs.

Aggressive behaviors of GISTs

As an alternative to the risk classification systems that stratify patients into distinct groups, others have quantified the risk of disease recurrence after complete resection as a continuous variable through the use of a GIST nomogram that includes the disease site [49]. Different nomograms have been developed by others as well.

GIST nomograms [49, 50] have been used to assess the risk of disease recurrence after complete resection as a continuous variable instead of the risk stratification systems that stratify patients into separate groups. Recently, a new risk stratification system has been developed in which tumor size and mitotic counts were assessed as continuous, nonlinear variables, and prognostic contour maps were then generated based upon these data plus site and tumor rupture [51]. These prognostic contour maps resulting from nonlinear modeling are used for the assessment of individualized outcomes.

Deletion type of mutations affecting codons 557 and 558 in KIT gene is considered a risk factor for recurrence regardless of different classification systems [4].

Pfetin is a prognostic biomarker which is still under investigation with promising results. Lack of Pfetin expression seems to be associated with a higher GIST recurrence [52]. Orita et al. [52]


**Table 1.** Different stratification systems for GISTs.

**5. Clinical picture**

72 Gastric Cancer - An Update

**6. Prognosis**

non-gastric GIST [46].

commonly used in clinical practice.

nomograms have been developed by others as well.

the assessment of individualized outcomes.

for recurrence regardless of different classification systems [4].

About 60% of GISTs occur in the stomach, 30% in the jejunum and ileum, 5% in the duodenum, 2–3% in the rectum, 1–2% in the colon, and < 1% in the esophagus [4]. About 70% of GISTs are symptomatic, 20% are asymptomatic, and 10% are discovered at autopsy [41]. The main symptoms of GIST are GI bleeding, abdominal discomfort, and abdominal mass. GISTs are highly vascular tumors and may grow quickly and cause massive gastrointestinal or intraperitoneal hemorrhage [42]. Obstruction symptoms such as dysphagia, obstructive

Extragastrointestinal GISTs occur in less than 10% of GISTs and mainly occur intra-abdominally and affect omentum and mesentery. Such tumors are considered more aggressive than

About 50% of patients will present with metastatic disease with the most common site of metastasis being liver at about 65%. Other common metastatic sites are omentum and peritoneum. Extra-abdominal metastasis, lung bone, and lymph node metastasis are not common [13].

Various risk stratification models (**Table 1**) have been proposed that are based on site, size, mitotic index, and tumor rupture. Gastric GISTs are known to have better prognosis than

Tumor rupture is known to be associated with a very high risk of GIST recurrence [47]. TNM staging is also available for GIST staging [48]. However, these stratification systems are not

As an alternative to the risk classification systems that stratify patients into distinct groups, others have quantified the risk of disease recurrence after complete resection as a continuous variable through the use of a GIST nomogram that includes the disease site [49]. Different

GIST nomograms [49, 50] have been used to assess the risk of disease recurrence after complete resection as a continuous variable instead of the risk stratification systems that stratify patients into separate groups. Recently, a new risk stratification system has been developed in which tumor size and mitotic counts were assessed as continuous, nonlinear variables, and prognostic contour maps were then generated based upon these data plus site and tumor rupture [51]. These prognostic contour maps resulting from nonlinear modeling are used for

Deletion type of mutations affecting codons 557 and 558 in KIT gene is considered a risk factor

Pfetin is a prognostic biomarker which is still under investigation with promising results. Lack of Pfetin expression seems to be associated with a higher GIST recurrence [52]. Orita et al. [52]

gastric GIST and have a poorer prognosis similar to small bowel GISTs [43, 44].

jaundice, and small bowel obstruction may also occur [42].

had 45 GIST cases, of which 37 were in the stomach. All GIST patients had R0 resection. There were seven recurrences with five recurrences being gastric GIST recurrences. Thirteen GIST patients were Pfetin negative and 5/13 Pfetin negative GISTs had recurrences [52].
