Gastric GIST mimicking adenocarcinoma

Clinical History

A 52-year-old woman with no relevant medical history was admitted to the ER with upper GI bleeding and haemodynamic instability. Oesophagogastroduodenoscopy (EGD) showed a polypoid lesion with an adherent clot in the body-antrum transition of the stomach (Fig. 1), which was biopsed.

Imaging Findings

A thoracic, abdominal and pelvic CT scan was performed. Pre-contrast images of the abdomen and post contrast images of the thorax, abdomen and pelvis, in the portal phase of enhancement, were obtained (Figures 2 and 3). A 3.4 cm polypoid lesion with an irregular surface, originating from the anterior gastric incisure, was detected. The lesion was homogeneous on the pre-contrast images. After iodinated IV contrast, it showed a thick, peripheral rim of hyper-attenuation, in continuity and with a similar enhancement compared to the surrounding normal mucosa. No signs of extramural growth, invasion of adjacent structures or distant metastasis were found.

Discussion

Patient presented with a relatively large, endophytic-growing tumour of the stomach with slightly lobulated margins and a thick, irregular rim of hyper-enhancing tissue mimicking a thickened mucosal layer. It was thus considered likely to be an adenocarcinoma, for which, given the location and absence of signs of local invasion or metastatic disease on CT, a total gastrectomy would be the oncologic curative surgery of choice. In a critically ill patient thought, such as this patient, minimal resection or haemostasis alone are preferred, due to the higher morbidity and mortality of major surgery. Patient was stabilised with aggressive fluid resuscitation making time for histopathologic analysis, which showed a tumour constituted by whirled bundles of fusiform cells with slight anisocariosis, expressing CD117 and CD34 intensely and diffusely, compatible with GIST. An atypical gastric resection was then performed and the diagnosis was later confirmed by histopathologic analysis of the (R0) surgical specimen (Figure 4).
Gastrointestinal stromal tumors (GIST) arise from the interstitial cell of Cajal or its precursor in the myenteric plexus and are the most common non-epithelial tumours of the GI tract, stomach being the most frequent location. Clinical manifestations depend on location but are often nonspecific.
CT is considered the imaging modality of choice for the detection, staging, surgical planning and follow-up of patients with GIST. The majority of primary gastric GISTs appear as well-defined, extramural or intramural masses with varying attenuation. Large lesions tend to show inhomogeneous density, with combined intraluminal and extramural growth and a tendency to spread to surrounding structures. They frequently show central areas of necrosis/haemorrhage. Furthermore, the cavities that develop from central necrosis/haemorrhage may communicate with the gastric lumen. Endophytic growing GISTs represent only 18-22% of all cases and tend to be small and hypoenhancing.
The differential diagnosis between gastric submucosal lesions, such as GISTs, and mucosal lesions, such as adenocarcinoma, is very important. CT imaging features such as smooth contour, right or obtuse angles with adjacent wall, intramural or exophytic growth and an overlying normal-thickness mucosal layer favour a submucosal origin (Figure 5). However, exceptions do occur and must be borne in mind before critical patient management decisions are made.

Differential Diagnosis List

Final Diagnosis

Gastric gastrointestinal stromal tumour

URL:	https://www.eurorad.org/case/10816
DOI:	10.1594/EURORAD/CASE.10816
ISSN:	1563-4086