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    • Preoperative imaging modalities such as contrast enhanced ab

    2018-10-29

    Preoperative imaging modalities, such as contrast-enhanced abdominal CT, facilitate diagnosis. Helical CT plays a crucial role in the diagnosis of intraluminal or exophytic tumors. The differential diagnosis of GI tract tumors should include fibromatosis, leiomyoma, schwannoma, inflammatory fibroid polyp, and leiomyosarcoma. CT is the most frequently performed imaging modality to locate the site of origin of tumors; the extent of the tumor, metastases, and involvement of other organs can also be assessed. Dedicated magnetic resonance imaging provides more detailed information than does CT in a preoperative staging workup. Although extraluminal in origin, GISTs may ulcerate through the overlying mucosa, causing intraluminal bleeding. The stromal collagen is minimal in most GISTs; however, delicate, thin-walled vessels may be prominent, rendering stromal hemorrhage a common feature of these tumors. Bleeding into the peritoneal cavity because of a ruptured GIST can engender acute abdominal pain, presenting a surgical emergency. The mechanism underlying hemoperitoneum may be related to bleeding in the tumor, leading to hematoma and rupture of the hydroxychloroquine sulfate Supplier or transudation of blood components from the tumor. In addition to the tumor size, mitotic rate, and tumor location, tumor rupture is considered a prognostic factor for outcomes in patients with GISTs. Metastatic seeding typically occurs in the peritoneal cavity and liver, followed by the lungs and bones. Preoperative percutaneous fine-needle aspiration of tumors for diagnostic purposes is not indicated because of the risk of potential intraperitoneal migration or tumor rupture. For GISTs, prognostic markers, namely tumor size > 5 cm, mitotic rate > 5/50 high-power fields, tumor necrosis, and Ki-67 (MIB-1) index > 10%, are all associated with tumor malignancy and high mortality. The main prognostic factor is the mitotic count. Fletcher et al defined a prognostic classification that is widely accepted and used presently. Pathological factors that can be used to determine malignancy are the tumor size, mitotic activity, nucleus pleomorphism, cellularity degree, nucleus to cytoplasm ratio, and mucosal invasion. The presence of the kit protein (CD117), a transmembrane receptor linked to an intracytoplasmic tyrosine kinase, is the classic finding in GISTs, and 95% of all cases are CD117 positive. In most cases, strong positivity is observed for CD117 (∼95%) and CD34 (∼70%). Therefore, positive results for these proteins in immunohistochemical examination facilitate establishing the diagnosis. Most GISTs are > 5 cm in diameter at diagnosis, with a 10-cm diameter being associated with a higher risk of local or distant metastasis. The prognosis of GISTs is dismal when they present with symptoms or signs such as perforation or rupture, multifocal location, or metastatic lesions. Patients with localized or locally advanced tumors have a 5-year survival rate of 46%, except for those with metastatic or multifocal tumors. Such patients have a 5-year survival rate of 24%, probably because of peritoneal dissemination. Lymph node spread is rare, and formal lymph node dissection has no proven advantage. Our patient was diagnosed with a high-risk malignant GIST because of the tumor size and rupture. Because the rupture of a GIST is a critical prognostic factor that renders it a high-risk tumor, care must be taken during surgery to prevent complications such as iatrogenic perforations or ruptures. Imatinib mesylate has revolutionized the therapy of advanced GISTs and is the first effective, worldwide-approved nonsurgical treatment for inoperable and metastatic cases. GIST response to conventional chemotherapy is extremely poor (< 10%), whereas radiotherapy is used only in cases of intraperitoneal hemorrhage, when the precise location of the tumor is known, or for analgesic purposes. Targeted therapy using the tyrosine kinase inhibitor imatinib, a novel adjuvant treatment administered after surgery, increases survival, suppresses tumor growth, and has moderate toxicity.