Extra gastrointestinal stromal tumor with unusual size and rare localization: a case report

¹Gastroenterology, Cheikh Khalifa Bin Zayed Al Nahyan Hospital, Mohammed VI University of Health Sciences (UM6SS), Casablanca, Morocco, ²Radiology, Cheikh Khalifa Bin Zayed Al Nahyan Hospital, Mohammed VI University of Health Sciences (UM6SS), Casablanca, Morocco

^&Corresponding author
Fatima Belabbes, Gastroenterology, Cheikh Khalifa Bin Zayed Al Nahyan Hospital, Mohammed VI University of Health Sciences (UM6SS), Casablanca, Morocco

Introduction    

Previously categorized as leiomyomas, schwannomas, leiomyoblastomas, or leiomyosarcomas, gastrointestinal stromal tumors (GISTs) are a newly recognized tumor entity. They are now categorized as GISTs based on histology, immunohistochemistry, and molecular research [1]. Although GISTs are the most frequent sarcoma of the gastrointestinal tract, they are rare neoplasms that constitute only 0.1-3% of all gastrointestinal malignancies [2], and Extragastrointestinal stromal tumors (EGISTs) are even rarer [3]. Imaging, especially abdominal CT with multiple slices, is reliable for diagnosis and staging of the disease and monitoring after treatment. We report the case of a 72-year-old patient with an EGIST with an atypical size and localization, to discuss the clinical aspects, the challenging diagnosis and, therapeutic strategies. The question in our case is whether is it an EGIST or another intraperitoneal tumor. The rare location, large size, and atypical radiological appearance pose a problem of differential diagnosis and therefore the difficulty of management. Our observation underscores the interest in radiological and endoscopic investigations.

Patient and observation     

Patient information: we report the case of a 72-year-old patient, referred by a family physician, referred to our academic institution, with a history of inguinal hernia, successfully treated 15 years ago, with no particular family or psycho-social history, who presented with chronic abdominal pain. The patient reported progressive abdominal pain for more than three months with gastrointestinal disorders such as constipation, low dysphagia, and early postprandial vomiting, in the context of apyrexia and altered general state.

Clinical findings: the clinical examination at admission revealed an asthenic, apyretic, and conscious patient, in a bad general condition, with a poor performance status (PS) of 2. The abdominal examination found a diffuse abdominal contracture and a fixed periumbilical mass without murmur. The rest of the clinical exam was normal.

Diagnostic assessment: the first-line biological assessment revealed hypochromic microcytic anemia with a low hemoglobin level of 10.9g/dl and thrombocytosis of 537.000/m³. The rest of the biological investigation was normal. The thoracic-abdominal-pelvic computed tomography (CT) (Figure 1) showed a mass of the omental bursa of 17x10x20cm, not having contact with the stomach and displacing the duodenal-pancreatic block with loss of the fatty separation line. It came into contact with the abdominal aorta, the renal artery, the left liver, and the hepatic artery with the persistence of the separation line, it came into contact with the anterior abdominal wall, displaced the spleen, and came into contact with the kidney and the left adrenal gland, the descending colon, and the splenic artery, it came into contact with the ascending colon with loss of the dividing line in places. In addition, the presence of an abundant intraperitoneal effusion with infiltration of the mesenteric fat may be related to peritoneal carcinomatosis. The gastrointestinal endoscopy revealed severe uncomplicated grade D esophagitis, an aspect of extrinsic compression on the gastric cavity extended from the cardia to the duodenal bulb with erythematous gastritis (Figure 2). The endoscopic ultrasound (Figure 3), showed a voluminous cystic with a solid component intraperitoneal perigastric mass compressing the stomach, it contained large liquid areas separated by tissue septa. An aspiration of 450cc of hemorrhagic fluid was done (to reduce the risk of infection and relieve the patient). Endoscopic ultrasound-guided fine-needle aspiration biopsies of the tissue septa were performed to have a histological diagnosis. Even though the origin of this tumor was not clear, the differential diagnosis was the intraperitoneal desmoid. The anatomopathological study showed a morphological appearance of a largely necrotic malignant spindle cell proliferation, suggesting a GIST. Immunohistochemistry (IHC) showed a diffuse and intense expression of CKIT which was Discovered in Gastrointestinal tumor-1 (DOG1) by tumor cells. The search for KIT and Platelet-Derived Growth Factor Receptor-Alpha (PDGFRA) mutations was not carried out due to a lack of means.

Diagnosis: on the basis of the clinical, radiological, endoscopic, and anatomopathological data, the diagnosis of EGIST was retained.

Therapeutic interventions: after the multidisciplinary consultation meeting, the staff decided to start adjuvant therapy for 6 months, with Imatinib 400 mg, a tyrosine kinase inhibitor.

Follow-up and outcome of interventions: the patient was seen again in consultation after 6 months. He had a good clinical condition. A control thoracic-abdominal-pelvic (CT) is planned.

Patient perspective: the patient was satisfied with the overall management on admission.

Informed consent: the patient provided written informed consent regarding the publication of this case and the accompanying radiographic images.

Discussion     

GIST constitutes 0.1-3 % of tumors in the digestive tract [2], which appears in 6.8-14.5 cases per million people per year. It results from the anarchic proliferation of Cajal interstitial cells, the pacesetter of the peristaltic movement of the gastrointestinal tract [3]. The common sites for GIST are the stomach (50%-70%) and small intestine (20%-30%), including the duodenum, jejunum, and ileum. Other locations are the large intestine (5%), and the esophagus in 2%-5% of cases [4]. Extragastrointestinal stromal tumors are estimated at 5% of all GISTs [5], and they occur in the mesentery (7.7-29.4%), retroperitoneum (25.5-25.6%), and omentum (7.7-15.7%) EGIST in the omentum seems to be extremely rare [3]. In our case, the location of the tumor was in the omentum. Clinically these EGISTs may remain asymptomatic for a long time due to their deep location and extraluminal development [2], our patient reported progressive abdominal pain, constipation, low dysphagia, early postprandial vomiting with a fixed periumbilical mass in the clinical examination.

Preoperative diagnosis of EGIST is not common and it can be made with imaging, computed tomography (CT), or magnetic resonance imaging (MRI), which allows visualization of the tumor [6], but it doesn´t help us to differentiate it from other pathologies [2]. The exact origin of the tumor proliferation is not always easily determined by imaging It is the biopsy of the mass performed by the biliopancreatic echo-endoscopy that allowed us to conclude in favor of the stromal nature of the tumor. According to Ortiz-Rey et al [6], a fine needle biopsy for diagnostic purposes is very useful and widely indicated in EGIST. The particularity of our case is the localization and the voluminous size which can pose at the preoperative stage a problem of differential diagnosis, with leiomyosarcoma, fibrosarcoma, liposarcoma, solitary fibrous tumor, paraganglioma, schwannoma, and lymphoma.

The best treatment for localized stromal tumors is complete surgical excision with safety margins. The prognosis depends not only on the histopathological grade but also on the quality of the surgical excision, which must be performed in a single block and without tumor invasion [5]. Gastrointestinal stromal tumors (GISTs) and EGISTs were misunderstood until 2000, the epoch of the discovery of an activating mutation of the c-kit tyrosine kinase and the ability to target those mutations with Imatinib [4]. It is an anti-tyrosine kinase drug that was initially used in chronic myeloid leukemia [7]. Recent studies have revealed the anti-tumor effect of STI-571 in GIST [8]. To date, Chemotherapy with imatinib is the drug of choice for locally advanced or metastatic EGISTs, and it has made a great revolution in the natural history of the disease. Metastatic GIST and EGIST before imatinib discovery had six months of survival, in the 3 published studies after 3 years of follow-up, median survival has not already been reached [9]. In our case, imatinib was prescribed because of the high risk of recurrence of stromal tumors, the therapeutic protocol comprising imatinib as a neo-adjuvant is necessary for tumor reduction. A complete or partial response to imatinib according to the criteria of RECIST is an indication for resection as adjuvant therapy [10]. The location of GISTs is a significant prognostic factor [2]. The EGISTs and especially those with a large diameter bigger than 5 cm have generally a worse prognosis [8]. So, the tumor in our case has a bad prognostic. The limitation of this study was the unavailability of the investigation of KIT and PDGFRA mutations due to a lack of financial means.

Conclusion     

The main problem in our case was the positive diagnosis because an EGIST poses a differential diagnosis of the other intraperitoneal tumors. The differential diagnosis was very facilitated by the IHC test. The second challenge was to be able to offer treatment. The cross-sectional imaging evaluation and more precisely Contrast-enhanced abdominal and pelvic Computed Tomography (CT) scan is the investigation of choice for characterizing the lesion, staging, and follow-up. The origin and tumor behavior of EGISTs are a subject still to be investigated. The treatment of choice remains complete surgical resection in localized forms, but the discovery of Imatinib has made a great revolution in non-localized and metastatic forms, and it considerably improved its prognosis. The studies concerning this particular pathology should be expanded. Therefore, new drugs are now under evaluation to prolong the pharmacological activity of tyrosine kinase inhibition after the progression of the disease.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Patient management: Fatima Belabbes, Fahd Ghalim and Safa Ibork. Data collection: Nawal Bouknani. Manuscript drafting: Hajar Fadili. Manuscript revision: Fatima Belabbes and Rouibaa Fadoua. All authors approved final version of the manuscript.

Figures     

Figure 1: the thoracic-abdominal-pelvic computed tomography (CT) showed a huge mass of the omental bursa. Red arrow: the mass came into contact with arterial structures but they remain permeable

Figure 2: the gastrointestinal endoscopy showed severe uncomplicated grade D esophagitis with an aspect of extrinsic compression on the gastric cavity extended with erythematous gastritis: A) compression aspect on the fundus; B) compression aspect on the antrum

Figure 3: the endoscopic ultrasound showed a voluminous heterogenous perigastric lesion compressing the stomach with two components anechoic and echogenic, in contact with vessels

References