[The role of PET scan in gastrointestinal stromal tumors]

Gastrointestinal Stromal Tumors-A Mini Review

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. They are potentially malignant, and have an unpredictable evolution. The origin of these tumors is in the interstitial cells of Cajal, which are cells that are interposed between the intramural neurons and the smooth muscle cells of the digestive tract. GISTs are characterized by mutations in the gene c-Kit, but also other mutations, such as those of the platelet-derived growth factor receptor alpha. The most common locations of these tumors are the stomach and small intestine, although they can occur at any level of the digestive tract and occasionally in the omentum, mesentery and peritoneum. Most cases of GISTs are sporadic, and about 5% of cases are part of family genetic syndromes. The correct diagnosis of GIST is determined by histopathological examination and immunohistochemistry. According to histopathology, there are three main types of GISTs: spindle cell type, epithelioid type and mixed type. The therapeutic management of GIST includes surgery, endoscopic treatment and chemotherapy. The prognosis of patients with GIST varies depending on a number of factors, such as risk category, GIST stage, treatment applied and recurrence after treatment.

Recent advances in the management of gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is a rare but an important clinical entity seen in our clinical practice. It is the most common mesenchymal tumor of the gastrointestinal tract and most common malignancy of the small intestine. Although the exact prevalence of GIST is not known, the incidence of GIST has been increasing. GISTs arise from interstitial cells of Cajal. Most of the GISTs occur due to mutation in c-kit gene or platelet derived growth factor receptor alpha gene. 15% of GISTs do not have these mutations and they are called wild-type GISTs. Almost all GISTs express KIT receptor tyrosine kinase. Histologically, GISTs look like spindle cell tumors most of the time but they can be epitheloid or mixed type. The median size of GISTs varies from 2.7 cm to 8.9 cm. Clinically, patients with small GISTs remain asymptomatic but as the GIST size increases, patients present with various symptoms depending on the location of the GIST. Most of GISTs are located in the stomach or small bowel. Diagnosis is suspected on imaging and endoscopic studies, and confirmed by tissue acquisition with immunohistochemical staining. The aggressiveness of GISTs depends on the size, mitotic index and location. Surgical resection is the treatment of choice. But various endoscopic modalities of resection are increasingly being tried. Tyrosine kinase inhibitors are extremely useful in the management of large GISTs, unresectable GISTs and metastatic GISTs. Treatment options for metastatic GISTs also include radiotherapy, chemotherapy, hepatic artery embolization, chemoembolization and radiofrequency ablation.

[Gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GIST) are the most common sarcomas of the gastrointestinal tract. They affect all segments of the digestive tract. They develop from the interstitial cells of Cajal. Mutations in the Kit gene is present in 86% of cases and in PDGFR gene in 15% of cases. The marker CD 117 is present in 95% of cases. Surgery is the standard treatment in localized forms. The tyrosine kinase inhibitor, imatinib is standard in first-line metastatic gastrointestinal stromal tumors, as well as adjuvant treatment after surgery. Sunitinib is the standard in second line.

Colorectal gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm arising in the digestive tract, with an estimated prevalence of 15-20 per 1,000,000. GISTs are related to the interstitial cells of Cajal and are characterized by constitutive over-expression of the transmembrane tyrosine kinase receptor KIT. This is produced by a patognomonic mutation of the proto-oncogene c-kit that occurs in up to 90% of cases. Exon 11 is affected most frequently; exons 9 and 13 are less commonly involved. One-third of GISTs lacking KIT mutations exhibits alternative activating mutations in the PDGFRα gene. Colorectal GISTs represent about 5-10% of the cases, mainly located in the rectum that is the third common site. Benign GISTs are more common, but many tumors are of uncertain malignant potential; tumor size and rate of mitosis are still the most reliable criteria for assessing the risk of an aggressive behavior. Surgery is the first-line treatment for resectable non-metastatic colorectal GIST. Standard oncologic resection is inappropriate because skip metastases and lymphatic spread are rarely reported. Segmental colectomy with negative margins is recommended, and local excision is oncologically adequate in highly selected rectal tumors. Radical surgery alone is not always curative especially in high-risk GISTs, and half of patients develops local recurrences or distant metastases after R0 operation. Medical therapeutic strategies have rapidly evolved after the introduction of targeted molecular therapy. Efficacy and safety of imatinib mesylate was first demonstrated in patients with metastatic and unresectable disease. Adjuvant and neoadjuvant use of imatinib are promising therapeutic options to improve the outcome of surgery to downstage unresectable lesions and to allow less extensive resections.

[Imaging of gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GIST) arising from interstitial cells of Cajal, represent the first type of solid tumor, which is very sensitive to a specific molecularly targeted tyrosine kinase receptor blocker (i. e., imatinib). On CT, which is considered as the reference technique, GISTs typically present as large, well-delineated, heterogeneous and sometimes exophytic masses. In contrast with the absence of lymph node involvement, hepatic metastasis as well as mesenteric involvement can be observed. MR-enteroclysis is indicated to investigate the local extent of the disease in specific cases whereas MR imaging is used to detect hepatic metastasis. Because of a specific treatment, contrast-enhanced imaging is needed for the follow-up of treated tumors. Evaluation of tumor response to treatment is best assessed with CT which still remains the reference imaging technique whereas FDG-PET imaging is used in specific cases.

Surgical management of gastrointestinal stromal tumours

BACKGROUND

Over the past decade, gastrointestinal stromal tumours (GISTs) have served as a model for the application of tyrosine kinase inhibitors in the treatment of solid neoplasms. Operative and medical management of GISTs is rapidly evolving, but current guidelines appear restricted to basic non-organ-specific recommendations.

METHODS

A PubMed search was made of the English literature from 1998 to 2008 for references containing the terms 'gastrointestinal stromal tumours' and 'surgery'. This paper reviews the various operative strategies so far reported for GISTs within the digestive tract.

RESULTS

Many original procedures tailored to the specific characteristics of these rare sarcomas have been reported. GISTs exhibit distinct features, in particular an absence of metastases within locoregional lymph nodes. Operations requiring extended lymph node dissection, typically designed for adenocarcinomas, such as gastrectomy with extended lymph node dissection, Whipple's procedure and total mesorectum excision, are inappropriate for treating GISTs originating from the stomach, duodenum and rectum respectively.

CONCLUSION

GISTs allow the possibility of performing oncologically adequate but limited (wedge; segmental) resections. Such surgery can be carried out in a variety of ways, such as open, laparoscopic, trans-sacral or endoscopic.

[Not Available]

S. Taïeb, L. Ceugnart, F. Bonodeau, L. Vanseymortier, A. Adenis The management and the prognosis of gastrointestinal stromal tumors (GIST) have evolved rapidly with new targeted treatments. The aim of this paper is to assess the role of imaging not only for diagnosis but to quantify treatment response. RECIST criteria, which are the standard in assessment of post chemotherapy response in adult's solid tumors, can not be used in targeted therapy: the changes in lesion structures even if case of increasing volume are more specific to assess tumor response.

The synchronous occurrence of squamous cell carcinoma and gastrointestinal stromal tumor (GIST) at esophageal site

BACKGROUND

Esophageal squamous cell carcinoma is a relative common malignancy with a very poor prognosis, even adopting an integrated and multidisciplinary approach. According to the literature, gastrointestinal stromal tumors (GISTs) rarely originate from the esophagus. Moreover there are not reports of synchronous occurrence of squamous cell carcinoma and GIST at esophageal site.

CASE PRESENTATION

We describe a case of a 74 year old patient who underwent surgery for squamous cell carcinoma of the lower third of the esophagus with an incidental pathologic diagnosis of a concomitant GIST in the thoracic tract.

CONCLUSION

In literature there is no evidence of concomitant squamous carcinoma and GIST of the thoracic esophagus, even if esophageal GISTs are sometimes described. The occasional finding of this neoplastic lesion underlines the importance of a carefully pathological diagnosis for its identification. Surgery, followed by a multidisciplinary approach remains the first-line treatment in both squamous and stromal neoplasm.