Clinical History
Dysphagia and abdominal discomfort, not associated with nausea and vomiting.
Imaging Findings
A 39-year-old woman was admitted to our hospital complaining about dysphagia and abdominal discomfort during the past few months, not associated with nausea and vomiting.
An abdominal ultrasound examination performed before had shown a hypo-echoic rounded mass in the mesogastric region. The patient underwent a contrast enhanced MRI of the abdomen which showed a large lesion arising from the gastric wall, well defined and with lobulated contours, about 11 cm x 8 cm in size, with exophytic growth. The lesion appeared as a inhomogeneous mass composed of solid tissue and numerous cystic spaces. After intravenous injection of gadolinium an intense and inhomogeneous enhancement was observed (Fig. 1-2); the lesion seemed to be cleaved from the surrounding organs (Fig. 3). These findings were highly suggestive of a gastrointestinal stromal tumour (GIST).
The patient underwent an atypical gastric resection and cholecystectomy.
A GIST was the histological result, positive for CD 117, vimentin and CD34, negative for desmin and actin. The mitotic rate was 11 mitosis for 50/HPF. The specimen included four lymph-nodes which were found to be metastatic of a GIST (C-Kit +, CD 34+ ).
The lesion, in accord with the Fletcher classification, was classified as a high risk tumour.
Discussion
GISTs are rare but they are the most common mesenchymal neoplasms of the gastrointestinal tract. These non-epithelial tumours arise from the muscularis propria and they are thought to derive from the interstitial cells of Cajal.
The most frequent sites of occurrence are the stomach (60-70%) and the small intestine (20-30%). GISTs are histologically classified in three subtypes: spindle, epithelioid and pleomorphic cells, and they all express KIT protein (CD117 stem cell factor receptor), which can be detected immunohistochemically [1]. About 20% of GISTs are malignant; tumours smaller than 2 cm are generally considered benign with a very low risk of recurrence. According to the classification proposed by Fletcher, GIST’s behaviour depends on two parameters: mitotic index and tumour size. A new approach introduced by Miettinen has proposed to include in the classification, as a third parameter, the tumour location [2]. The clinical manifestations of a GIST depend on its location and size, but they are often non-specific, even when, as in our patient, the neoplasm presents as a large mass. Common symptoms include early satiety, bloating, dysphagia, palpable mass and bleeding [3].
50% of patients with GISTs present with metastases; most metastases involve the liver and the peritoneum, lymph-nodes are not a frequent site of a secondary localisation. In fact literature has shown that unlike other tumours of the GI tract, such as adenocarcinomas or lymphomas, the lymphadenopathies in GISTs are extremely rare: the frequency is 5% [1]; in this case, however, the loco-regional lymph nodes were involved. Imaging is important not only for the diagnosis but also to monitor the effects of the treatment both surgical and pharmacological.
MRI features of a gastric GIST vary depending on the size of the tumour. Small GISTs often appear as homogeneous solid masses, while tumours of larger size, as in our case, are often heterogeneous because of the presence of necrotic and haemorrhagic areas or cystic degeneration. GISTs typically show an exophytic growth and tend to displace adjacent organs, but invasion of adjacent structures is uncommon. Infrequently they can be endoluminal and polypoid in appearance. MRI is able to identify and to characterise the neoplasm; with multiplanar acquisition the site of origin and its dimensions, two important parameters to assess the prognostic behaviour, can be determined [4, 5].
The treatment of choice is the complete surgical resection and the medication with tyrosine-kinase inhibitor (Imatinib) [4].
Differential Diagnosis List
Gastrointestinal stromal tumour with lymph nodes metastases
Adenocarcinoma
Leiomyoma
Leiomyosarcoma
Final Diagnosis
Gastrointestinal stromal tumour with lymph nodes metastases
