Gastrointestinal Stromal Tumor

 presenting as a Gastric Mass :

A Case Report

Benjamin C. Deveza, M.D.

Janix M. De Guzman, M.D.

Edgardo Penserga, M.D., FPCS, FPSGS

Reynaldo Joson, M.D., MHA, MHPEd, MS Surg

Department of Surgery

Ospital ng Maynila Medical Center

Key words : gastrointestinal stromal tumors (GIST); gastric mass

Reprint request : Benjamin C. Deveza, M.D.

Department of Surgery, Ospital ng Maynila Medical Center

OMMC Surgery@yahoogroups.com

Abstract

A female Filipino presented with black tarry stools and was admitted at Internal Medicine as a case of Upper Gastrointestinal Bleeding secondary to Peptic Ulcer Disease. On further work-up, through abdominal  CT scan, there was a large lobulated mass in the gastric body, lesser curvature aspect, measuring about 5 x 3.7 x 4.9 cm. There is thickening of the wall as well as in the greater curvature across the mass. There is marked narrowing of the gastric lumen at this point.Liver, gallbladder, pancreas, spleen and adrenal glands are normal. Impression was a Gastric Malignancy. Patient was then transferred to the Department of Surgery for further evaluation and management. She underwent subtotal gastrectomy, Billroth II and jejuno-jejunostomy. Histopathology of gastric mass revealed Gastrointestinal Stromal Tumor ( GIST ), lesser curvature, stomach. Patient was discharged improved after nine days and was monitored closely on follow-up. Discussion centered on Gastrointestinal Stromal Tumors (GIST) as the newer classification for smooth muscle tumors of the gastrointestinal tract.

Introduction

Gastric stromal tumors are generally called gastrointestinal stromal tumors (GISTs). They are mesenchymal gastrointestinal (GI) neoplasms defined by the expression of KIT (CD117) in the tumor cells. Previously, these tumors were classified as gastric or intestinal smooth muscle tumors; however, this traditional classification was abandoned with the availability of immunohistochemical methods verifying this specific entity. GISTs are rare and constitute only about 1% of all GI malignant tumors, nevertheless, they are the most common mesenchymal neoplasm of the GI tract. GISTs are found in the stomach in 47-60% of cases, yet they are the least prevalent malignant tumors of the stomach, constituting 1-3% of all malignant gastric tumors.

            This is a case report of a female Filipino patient who was initially assessed to have Upper Gastrointestinal Bleeding secondary to Peptic Ulcer Disease but on further work-up was found to have a Gastric Malignancy.

            This case report is made to develop the awareness on Gastrointestinal Stromal Tumors (GIST) as the newer classification for gastric stromal tumors.

Case Report

This is a case of a 55-year-old female from Pandacan, Manila who was admitted because of black tarry stools. History of present illness started four days prior to admission when she experienced vague abdominal pain. This was accompanied by passage of black stools and coffee ground vomitus. Persistence of symptoms prompted consult at our institution where she was subsequently admitted at Internal Medicine. Past medical history revealed that she was diagnosed with Osteoarthrtis since 2001 and was maintained om Mefenamic acid and Rofecoxib. She denied any heredofamilial disease. On physical examination, she was conscious, coherent with stable vital signs. She had pale palpebral conjunctiva. On rectal examination, there was black tarry stools on the examining finger. The rest of the physical examination was essentially normal. Impression at that time was Upper Gastrointestinal bleeding secondary to Peptic Ulcer Disease. At the wards, she was hooked to IV fluids. Endoscopy was done which revealed a 5x5 smooth surfaced mass with mucosal erosions with active bleeding. Abdominal CT scan was likewise done and revealed a large lobulated mass in the gastric body, lesser curvature aspect, measuring about 5 x 3.7 x 4.9 cm. There is thickening of the wall as well as in the greater curvature across the mass. There is marked narrowing of the gastric lumen at this point.Lliver, gallbladder, pancreas, spleen and adrenal glands are normal.

            Impression: Gastric Malignancy

            At this time, patient was transferred to the Department of Surgery for further evaluation and management. She was then prepared for operation. She underwent subtotal gastrectomy, Billroth II and jejuno-jejunostomy. Intraoperatively, there was a 5x5x4.5 cm submucosal mass on the lesser curvature of the stomach with mucosal ulcerations. A solid mass with central necrosis was also noted. Final histopathological report showed a Gastrointestinal Stromal Tumor (GIST), lesser curvature, stomach.

            Post-operative course was uneventful. She was discharged after nine days and oral medications were continued at home. Follow-up was made after one week.

Discussion

Histologically GISTs vary from cellular spindle cell tumors to epithelioid and pleomorphic ones. By definition they are CD-117 positive, although positivity for nestin and CD34 is also common but not specific. Predictive of malignancy are mitotic rate over 5 per 10 high-power fields (HPFs) or size over 5 cm. However, tumors with low mitotic index can also metastasize, and gastric tumors are commonly less aggressive that the intestinal ones.

GISTs are typically diagnosed as solitary lesions, although in rare cases, multiple lesions can be found. These tumors can grow intraluminally or extraluminally, toward the abdominal cavity and adjacent structures. When the growth pattern is extraluminal, patients can be symptom free for a long time and present with very large exogastric masses. Distant metastases tend to appear late in the course of the disease in most cases. In contrast to other soft tissue tumors, the common metastatic sites of gastric stromal tumors are the liver and peritoneum. Lymph node involvement is rare and is in the range of 0-8%.

Clinical Features

•       Race: No racial predilection exists.

•       Sex: Gastric stromal tumor is not more prevalent in either sex.

•       Age: Onset can occur at any age, but the typical age of onset is in the sixth to seventh decades of life.

•         Causes: No risk factors have been identified.

History:

•       Upper GI bleeding - most common clinical manifestation of gastric stromal tumor, manifesting as hematemesis or melena and observed in 40-65% of patients. Bleeding occurs because of an ulcer forming in the gastric mucosa overlying the tumor.

•       Other symptoms may include abdominal pain, anorexia, nausea, vomiting, weight loss, epigastric fullness, and early satiety.

Physical:

•       Physical examination rarely demonstrates any significant findings. In some cases, examination may identify a palpable abdominal mass in the upper abdomen. Palpable masses are typically detected in patients with an exogastric tumor growth.

Imaging Studies:

• Computed tomography scanning of the abdomen: Abdominal CT scanning with intravenous and oral contrast material is a necessary step in the evaluation of these patients. The gastric mass can be detected originating from the gastric wall. CT scanning can also be used to evaluate tumor invasion to adjacent structures and the presence of intra-abdominal metastasis. As mentioned, findings on CT scanning can often be confused with masses originating from adjacent structures.

• Endoscopic ultrasonography: Endoscopic ultrasonography (EUS) is a valuable tool in the diagnosis and preoperative assessment of gastric stromal tumors. It can demonstrate the submucosal location of the tumor and can define its size, borders, and echoic pattern. Ultrasonic features associated with increased risk of malignancy are large tumors, tumors with irregular extraluminal borders, and the presence of cystic spaces and echogenic foci. Diagnosis can often be made using ultrasonographic-guided biopsy. However, the histology obtained can demonstrate a spindle cell tumor but can hardly differentiate between benign and malignant forms.

Preoperative biopsy: Preoperative biopsy is not always indicated. Surgical resection is required for treatment and for definitive diagnosis in most cases. Biopsy is important when the submucosal nature of this tumor is in doubt or when tumor characteristics as demonstrated by upper endoscopy and endoscopic ultrasonography are not typical. In specific patients, such as high-risk operative patients with small benign-appearing lesions and minimal or no symptoms, tissue diagnosis may help in further decision-making. The 2 ways to obtain a preoperative histologic diagnosis are as follows:

• Endoscopic biopsy: Preoperative endoscopic biopsy may be taken with or without EUS guidance. When taken without the help of EUS, endoscopic biopsy is not accurate and leads to a correct diagnosis in less than 50% of patients. Biopsies may miss the tumor and show only mucosal tissue. In addition, samples from the tumor itself often are too small to establish malignant nature. EUS-guided biopsy is more accurate. This technique can achieve a correct histologic diagnosis in more than 80% of cases and should be performed whenever preoperative histology seems necessary.

• Percutaneous biopsy: Tumor biopsy can be obtained percutaneously under CT scanning or ultrasonographic guidance. Consider this procedure in selected patients when endoscopic biopsy results are negative or biopsy is impossible to perform.

Treatment:

–        Resection to achieve a negative microscopic margin (1-2cm adequate)

–        Routine lymphadenectomy is not indicated and does not show any survival benefit.

–        Direct every effort at avoiding tumor rupture during the operation. Tumor rupture is associated with a worse prognosis because of peritoneal seeding

–        In cases of disseminated disease, consider palliative resection because long-term survival has been reported in certain cases.

Prognosis:

Long-term survival for malignant GIST after a curative-intent surgery is strongly related to tumor size and histologic grade

–        5-year survival rates after R0 resection for gastric stromal tumors range from 32-93%. In large series, this rate is about 60%.

–        median survival after palliative resection is about 10 months, with a 5-year survival rate as high as 10%.

–        Histologic grade alone is a strong prognostic factor. In 1982, Shiu et al reported a 5-year survival rate of 80% in patients after resection of low-grade tumors. The 5-year survival rate dropped to 32% in patients with high-grade tumors.

–        Other factors found to have a negative impact on prognosis are tumor rupture during operation, involvement of histologic margins, and lymph node involvement.

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