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AJR 2004; 183:1844-1846
© American Roentgen Ray Society

Mesenteric Gastrointestinal Stromal Tumor in a Patient with Neurofibromatosis

Rakesh Sinha, Ratan Verma and Andrew Kong

Leicester Royal Infirmary Leicester LE1 5WW, England
Glenfield Hospital Leicester LE3 9QP, England
Lyell McEwin Health Service Elizabeth Vale 5112, South Australia

Gastrointestinal stromal tumors (GISTs) are the most common tumors of mesenchymal origin in the gastrointestinal tract, mesentery, omentum, and retroperitoneum. Most GISTs arise in the stomach. The most significant risk factor for development of these tumors is the presence of neurofibromatosis type 1 (NF1) [1]. Other risk factors include urticaria pigmentosa and the very rare familial GIST syndrome. Although the increased incidence of GISTs in patients with neurofibromatosis is well documented, especially in the pathologic and genetic scientific literature, this association has rarely been documented in the imaging literature. To our knowledge, this is the first imaging report of a patient with neurofibromatosis and a coexistent GIST.

A 57-year-old man presented with symptoms of gradually increasing abdominal distention and left upper quadrant pain. He had been previously diagnosed with NF1. Clinical examination revealed a palpable nonpulsatile abdominal mass in the upper abdomen. Cutaneous stigmata of neurofibromatosis were noted, and several neurofibromas were present on the patient's back.

CT of the abdomen and pelvis showed a large 13 x 15 cm mass in the upper abdomen that appeared to arise separately from the stomach and the small bowel. This mass showed heterogeneous attenuation and irregular peripheral enhancement (Fig. 7A). Central areas of hypodensity were present on the enhanced scans, in keeping with cystic change. The liver, pancreas, spleen, and both kidneys appeared normal with evidence of ascites.



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Fig. 7A. 57-year-old man who presented with symptoms of gradually increasing abdominal distention and left upper quadrant pain. CT scan shows large mesenteric mass lesion with irregular peripheral enhancement and central cystic areas arising from gastrohepatic ligament.

 

CT also showed a dumbbell-shaped isodense mass in the region of the right S1 neural foramen with distortion and expansion of the exit foramen (Figs. 7B and 7C). On the basis of radiologic findings, a diagnosis of mesenteric GIST was suggested along with a sacral neurofibroma. The abdominal tumor was surgically excised. Histologic findings showed an intermediate-grade GIST in the lesser sac that arose from the gastrohepatic ligament with positive immunoreactivity to the tyrosine kinase growth factor receptor (KIT [CD 117]) stain. Histologic diagnosis of the lesion in the sacral nerve root from a tissue sample obtained at biopsy confirmed the diagnosis of a neurofibroma.



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Fig. 7B. 57-year-old man who presented with symptoms of gradually increasing abdominal distention and left upper quadrant pain. CT scan shows dumbbell-shaped mass with expansion of right S1 neural foramen.

 


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Fig. 7C. 57-year-old man who presented with symptoms of gradually increasing abdominal distention and left upper quadrant pain. Sagittal reformatted CT scan shows mesenteric and sacral masses (arrow).

 

GISTs are the most common mesenchymal tumors of the gut. Their defining characteristic is the expression of KIT (CD 117). GISTs are thought to arise from the KIT-positive autonomic pacemaker cells in the gut called the interstitial cells of Cajal. The incidence of GISTs is estimated to be between 10 and 20 cases per million, and they usually occur in patients who are older than 50 years. GISTs are the most common smooth-muscle tumors arising in the gastrointestinal tract from the stomach to the anal canal. Other smooth-muscle tumors such as leiomyomas are very rare in these sites (the esophagus is the only site in the gastrointestinal tract in which leiomyomas predominate). The stomach is the most common site for the development of GISTs, which account for approximately 2–3% of all gastric tumors [2]. Less than 1% of gastrointestinal stromal tumors occur in the mesentery, omentum, or retroperitoneum [3].

GISTs have a known association with NF1. Gastrointestinal involvement in NF1 occurs in three principal forms: hyperplasia of the submucosal and myenteric nerve plexuses and mucosal ganglioneuromatosis; GISTs with varying degrees of neural or smooth-muscle differentiation; and a glandular, somatostatin-rich carcinoid in the periampullary region of the duodenum that contains psammoma bodies and may be associated with pheochromocytoma. In a large series of 156 GISTs, 6.5% of the cases involved coexistent NF1 [4]. Typically patients with NF1 have multiple small intestinal GISTs [2]. Patients with NF1 also have increased incidence of neuromas and schwannomas occurring in the gastrointestinal tract. Other conditions that predispose patients to an increased incidence of GISTs are Carney's complex and urticaria pigmentosa. Carney's complex is a rare condition that comprises an association among extraadrenal paragangliomas, pulmonary chondromas, and epithelioid leiomyosarcomas. Families with KIT germ line mutations also have an increased incidence of GISTs.

Clinical symptoms are related to the size and location of the GISTs. Most pathologists use a combination of tumor size and mitotic rate to assess the malignant potential of these tumors. In general, malignant GISTs are larger, more cellular, and more mitotically active. GISTs that are smaller than 5 cm with five mitoses per 50 consecutive high-power fields or less are considered to be benign with a low risk for metastasis. Tumors larger than 10 cm with more than five mitoses per 50 high-power fields are considered to be malignant. All tumors falling between these two extremes are considered to be of uncertain malignant potential with intermediate risk for metastasis. Tumors with more than 50 mitoses per 50 high-power fields are considered to be highly malignant with an aggressive clinical behavior. The liver and the peritoneum are the most common sites of spread in malignant GISTs [5].

Mesenteric GISTs are rare and may arise as a primary lesion or as a result of metastatic spread. Usually metastatic mesenteric GISTs are multiple and may simulate peritoneal carcinomatosis. In the series reported by Miettinen et al. [6], the average size of mesenteric GISTs was 16.5 cm. On CT, mesenteric GISTs are usually well-defined, lobulated masses that predominantly show heterogeneous contrast enhancement. Central areas of hypodensity commonly are present because of necrosis or intratumoral hemorrhage. Intratumoral calcification is uncommon. Usually the appearance is that of a complex, partially cystic mass that is indistinguishable from other mesenchymal tumors. The usual treatment of such tumors is surgical excision, although recently treatment targeted toward inhibiting the mutant KIT gene by tyrosine kinase inhibiting agent (STI-571) in recurrent cases has also been very successful.

This case illustrates the increased prevalence and association of GISTs in patients with NF1. The occurrence of an intraabdominal mass with central liquefaction should point toward the diagnosis of a GIST. Conversely, the medical history of NF1 in a patient who has an intraabdominal mass with nonspecific CT features may help in diagnosing a GIST by virtue of the well-known association of these two entities.


References
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References
 

  1. Fletcher CD, Berman JJ, Corless C, et al. Diagnosis of gastrointestinal stromal tumours: a consensus approach. Hum Pathol 2002;33:459 –465[Medline]
  2. Levy AD, Remotti HE, Thompson WM, Sobin LH, Miettinen M. Gastrointestinal stromal tumors: radiologic features with pathologic correlation. RadioGraphics2003; 23:283 –304, 456[Abstract/Free Full Text]
  3. Burkill GJC, Badran M, Al-Muderis O, et al. Malignant gastrointestinal stromal tumor: distribution, imaging features, and pattern of metastatic spread. Radiology2003; 226:527 –532[Abstract/Free Full Text]
  4. Miettinen M, Kopczynski J, Makhlouf HR, et al. Gastrointestinal stromal tumors, intramural leiomyomas, and leiomyosarcomas in the duodenum: a clinicopathologic, immunohistochemical, and molecular genetic study of 167 cases. Am J Surg Pathol2003; 27:625 –641[Medline]
  5. De Matteo RP, Lewis JJ, Leung D, Mudan SS, Woodruff JM, Brennan MF. Two hundred gastrointestinal stromal tumours: recurrence patterns and prognostic factors for survival. Ann Surg2000; 231:51 –58[Medline]
  6. Miettinen M, Monihan JM, Sarlorno-Rikala M, et al. Gastrointestinal stromal tumors/smooth muscle tumors (GISTs) primary in the omentum and mesentery: clinicopathologic and immunohistochemical study of 26 cases. Am J Surg Pathol1999; 23:1109 –1118[Medline]

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