Gastrointestinal stromal tumors with pseudocystic change mimicking a pancreatic tumor: two case reports

Pancreatic Gastrointestinal Stromal Tumor: Clinicopathologic Features and Prognosis

GOALS

The present study aimed to investigate the clinicopathologic features and prognosis of pancreatic gastrointestinal stromal tumor (GIST).

BACKGROUND

Reports on clinicopathologic features and prognosis of pancreatic GIST are limited due to the extremely rare incidence.

STUDY

One case of pancreatic GIST from our center and 44 cases reported in MEDLINE were enrolled in this study. Clinicopathologic features and prognosis of pancreatic GISTs were analyzed and compared with 297 gastric GISTs from our center.

RESULTS

The most common location was head of pancreas (38.5%). The majority of pancreatic GISTs exceeded 5 cm (74.4%), displayed cystic or mixed imaging features (56.4%), and were high risk (85.7%). The 5-year disease-free survival (DFS) and disease-specific survival rates were 66.1% and 95.8%, respectively. Mitotic index was the only risk factor for DFS of pancreatic GISTs. The distribution of tumor size, histologic type and National Institutes of Health risk category were significantly different between pancreatic and gastric GISTs. The 5-year DFS rate of pancreatic GISTs was significantly lower than that of gastric GISTs. Multivariate analysis showed that location was an independent prognostic factor for DFS between pancreatic and gastric GISTs.

CONCLUSIONS

The most common location was head of pancreas. The majority of pancreatic GISTs were large and highly malignant. Pancreatic GISTs differed significantly from gastric GISTs in respect to clinicopathologic features. The DFS of pancreatic GISTs was worse than that of gastric GISTs.

Atypical presentation of gastrointestinal stromal tumor masquerading as a large duodenal cyst: A case report

INTRODUCTION

Gastrointestinal stromal tumors (GIST) are solid tumors. A duodenal GIST masquerading as a cystic lesion has never been reported. We report a large duodenal cyst that finally turned out to be a GIST and was managed without a pancreaticoduodenectomy (PD).

PRESENTATION OF CASE

A 55 year old lady presented with painful lump in epigastrium. A CT scan revealed a large exophytic cystic lesion from the duodenum with a small solid component. An endoscopy showed a polypoid lesion in the second part of the duodenum adjacent to what looked like a diverticulum. A sleeve duodenal resection, duodeno-duodenostomy and pyloric exclusion was done. The histopathology was duodenal GIST.

DISCUSSION

This case posed diagnostic difficulty as it was thought to be either a duplication cyst or a diverticulum of duodenum. The odd point was the small solid component in it. We considered the possibility of a malignancy arising in these settings, which is has been occasionally reported. To our surprise, it turned out to be a GIST. An extensive literature search yielded only four reports that have reported cystic GISTS, all arising from the stomach or pancreas where they have been mistaken for pseudocysts or even a mucinous cystadenocarcinoma of the pancreas. This is the first report of a cystic GIST arising from the duodenum.

CONCLUSION

GISTS can present as a predominantly cystic lesion and needs to be considered in the differential diagnosis of cystic lesions of the duodenum. Local resection is an attractive option in select cases and avoids a PD.

Unusual features of gastrointestinal stromal tumor on PET/CT and CT imaging

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. It can be benign or malignant in behavior. Stomach, being the most common site (70%) for GISTs, is followed by the small intestine (20%). Anorectal, colonic, and esophageal GISTs are uncommon, whereas extraintestinal GISTs are extremely rare. The presenting symptoms are highly dependent on tumor size and location, although a large number of GISTs are asymptomatic. The purpose of this article is to highlight the unusual characteristics of GISTs illustrated by PET/CT and CT imaging. These characteristics are organized into (1) unusual tumor location, (2) unusual clinical presentation, and (3) unusual sites of metastasis. Knowing the uncommon features of GISTs is important, as they are more often seen nowadays with the increasingly important role of PET/CT and CT in GIST management; and these tumors are associated with a poorer prognosis and unwanted delay in diagnosis is avoidable. With the availability of effective treatment by imatinib mesylate, a prompt and early diagnosis is essential for disease control. All GISTs illustrated in this article are pathologically proven.