A Diagnostic Surprise For A Right Iliac Fossa Mass – A Perforated Ileal Gastrointestinal Stromal Tumour

Gastrointestinal Stromal Tumours (GISTs) are tumours of the gut found mostly in stomach and small intestine. The complications are Gastrointestinal (GI) bleeding, obstruction, pain and rarely perforation. We are reporting an abnormal presentation of GIST masquerading as an acute abdomen with Right Iliac Fossa (RIF) mass in 60-year-old lady. Contrast Enhanced Computed Tomography (CECT) of abdomen revealed a peripherally enhancing encapsulated abscess in RIF in close contact with base of caecum and adjacent peritonitis suggesting caecal perforation. On laparotomy, a gangrenous perforated ileal GIST was identified along the antimesenteric border of ileum. Pathological examination confirmed the tumour to be a GIST of spindle cell type, further reiterated by immunohistochemistry. Our case report emphasizes, GIST as a rare and unusual differential diagnosis of RIF mass, and to have high degree of clinical suspicion when a similar situation is encountered in an emergency scenario, keeping in mind the poor outcome due to delay in appropriate management of the disease.

A 60-year-old female presented to the Emergency room with complaints of diffuse lower abdominal pain for one day duration with three episodes of haematochezia over eight hours duration. On examination, she had pallor and tachycardia. On clinical examination of abdomen, there was tenderness, mild guarding, rebound tenderness and an ill defined mass in the right iliac fossa. On rectal examination, blood staining of digit was present. The laboratory tests showed haemoglobin of 8 gm% and leukocytosis 16000 cells/mm³. Chest and abdomen X-rays were normal. Ultrasound abdomen reported an ill defined mass in RIF with minimal free fluid and probe tenderness. CECT of abdomen demonstrated a peripheral enhancing, encapsulated abscess in RIF, in close contact with base of caecum and adjacent peritoneal inflammation, suggesting a sealed caecal perforation [Table/Fig-1].

[Table/Fig-1]:

CECT abdomen showing an encapsulated abscess in RIF in close contact with the base of caecum with adjacent peritoneal inflammation.

Operative findings: She underwent an emergency exploratory laparotomy which revealed a part of the small bowel and omentum adherent to the caecum and adjacent abdominal wall. Slow separation and blunt dissection of the structures revealed a gangrenous, perforated small bowel tumour of maximum diameter 6 cm-8 cm at the antimesenteric border of the ileum nearly, 80 cm proximal to the ileocecal junction [Table/Fig-2,3]. Rest of the abdomen was normal. She underwent segmental resection of ileum with part of the mesentery and primary anastomosis. The peritoneal cavity was irrigated with copious amount of normal saline and abdomen was closed in layers.

[Table/Fig-2,3]:

A perforated and gangrenous GIST at the antimesenteric border of ileum.

Pathological findings: Pathological examination revealed a 6 cm x 5 cm x 3 cm submucosal mass extending into the antimesenteric border of ileum. Microscopy revealed a low grade, intermediate risk, pT3 pNx GIST of spindle cell type. Immunohistochemistry was positive for CD117 confirming the diagnosis of GIST [Table/Fig-4].

[Table/Fig-4]:

Immunohistochemical staining(IHC 400X) positive for CD117 (c-Kit).

Postoperative course: Her postoperative course was uneventful. She was discharged on the tenth postoperative day after suture removal. She was started on adjuvant imatinib therapy to prevent tumour recurrence.

GIST are tumours of mesenchymal origin that arise from interstitial cells of Cajal in GIT. They constitute 0.1%-3% of all Gastrointestinal Tract (GIT) tumors [1]. GISTs typically occur in the elderly around the sixth decade of life [2]. They can occur anywhere in the GIT but mostly observed in the stomach (50%) and small intestine (25%). GISTs generally have an indolent course and are diagnosed incidentally. Small sized tumours remain silent while large sized tumours present as large abdominal masses with clinical features unrelated to the disease, so most metastasize at the time of presentation [2,3]. The complications are GI bleeding (40%), intestinal obstruction, abdominal pain and very rarely perforation [2].

GIST as a content of Meckel’s diverticulum has been reported in seven cases [4] and as abdominal cocoon in a single case [5]. Most common complication of GIST is bleeding [2] but they have also presented rarely as perforation which has been documented in seven cases [6]. There are only two documented cases till now of GIST presenting as RIF mass, one a jejunal GIST masquerading as an appendicular mass [7] and another a cecal GIST presenting as a diffuse swelling in RIF and right lumbar regions [8]. In our case, a perforated terminal ileal GIST presented as a RIF mass with lower GI bleed. This combination of presentation is yet to be reported.

The pathological diagnosis is based on the histological profile of the tumour and immunohistochemical (IHC) staining is required to confirm the diagnosis [9]. The following table shows the IHC staining pattern of GIST [Table/Fig-5] [2,5,10-13].

Recently identified, antibody against DOG1 (discovered on GIST) was reported to be positive in 85%-95% of CD117-positive GISTs and in 30%-36% of CD117–negative GISTs. However, it cannot differentiate between KIT/PDGFRA mutant and wild-type GIST. Hence, DOG1 immunostaining may be helpful to identify tumours which cannot be diagnosed based on c-Kit immunohistochemistry [11].

Fletcher CD et al., proposed a classification system to prognosticate GIST and has been widely accepted and followed today [Table/Fig-6] [14]. The mitotic count is the most vital prognostic factor [10,12].

The preferred treatment of choice for GISTs is R0 surgical excision. A lymphadenectomy is usually not performed, as metastasis to lymph nodes is extremely rare. Patients with perforation have a five-year survival rate of only 24%, in contrast to patients with localized or locally advanced tumours where the five-year survival rate is 46%. The reason for this difference may be attributed to peritoneal dissemination [13]. Imatinib, a selective tyrosine kinase inhibitor therapy which has significantly improved the overall survival in patients with advanced disease. Adjuvant therapy should be considered for four years, in patients undergoing R0 resection for primary disease and perforation as well [15].

We presented this case of an acute abdomen with a RIF mass that was incidentally diagnosed to be a perforated GIST arising from the ileum. Apart from the usual causes of RIF mass, a perforated GIST of this kind should also be considered when older patients present with such clinical features. A high degree of clinical suspicion and prompt management is required in view of the high morbidity rates from delayed diagnosis of this disease.

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