An 84-Year-Old Man with Abdominal Distension and Confusion

CASE REPORT

An 84-year-old man presented with worsening confusion and agitation for the last few days. He also reported progressively increasing abdominal distension of several months' duration, more so over the last 3–4 months. The patient denied abdominal pain, nausea, vomiting, or alterations in bowel habits. He had a history of loss of appetite and an unintentional weight loss of 30 pounds over the last few months. Past medical history was significant for diabetes mellitus and lactose intolerance.

Physical examination revealed an elderly, cachectic, confused man with no focal neurologic deficit. His abdomen was markedly distended with dullness on percussion. Laboratory investigations were significant for elevated blood ammonia level (168 μmol/L), alanine aminotransferase (424 U/L), aspartate aminotransferase (153 U/L), alkaline phosphatase (102 U/L), and total bilirubin (1.7 mg/dL). Carcinoembryonic antigen and CA19-9 were within normal limits. Computed tomography (CT) images of the abdomen are shown in Figure 1. Photomicrographs obtained after CT-guided fine-needle aspiration biopsy (FNAB) of the liver are shown in Figure 2.

Figure 1.

Computed tomography images of the abdomen: axial view at the level of upper (left) and mid-abdomen (right), and sagittal view (center).

Figure 2.

Liver FNAB: H&E staining (left) and immunostaining for CD117 (right).

The CT scans of the abdomen revealed an extremely large, complex mass measuring 34 × 24 × 27 cm, filling almost the entire abdomen and pelvis. The mass was hypodense in the center with peripheral, irregular soft-tissue density. It appeared to arise from and replace all pancreatic tissue, giving the impression of a mucinous cystadenocarcinoma. Multiple hypoattenuated lesions were also seen in the liver parenchyma, suggestive of hepatic metastases. Subsequently a CT-guided FNAB of a hepatic lesion showed malignant spindle cells with immunocytochemistry positive for CD117 (c-KIT), CD34, and vimentin. Results were negative for smooth muscle and neuroendocrine markers. These findings are consistent with a histologic diagnosis of extragastrointestinal stromal tumor.

DISCUSSION

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that rarely develop outside the digestive tract; when they do, they are designated extra-GISTs (EGISTs), which make up about 5–7% of all GISTs.¹ The majority of EGISTs are located in the mesentery, omentum, and retroperitoneum.^1–3 Primary localization in the pancreas is rare and has been reported in only a few cases, with most of these tumors located in the body and tail of the pancreas.^4–7

GISTs are believed to originate from the interstitial cell of Cajal or related stem cells that express the c-kit protein (CD117), CD34, and vimentin.⁴ An EGIST or metastatic disease may mimic other mesenchymal tumors, such as sarcoma or myoma, on gross and microscopic appearance. The definitive diagnosis is based on immunohistochemical examination; c-kit (CD117) expression, which is found in >95% of GISTs, is the most sensitive marker.⁸

Because of the small number of EGIST cases that have been reported, the clinical features and treatment of this rare neoplasm are not well known, and prediction of the malignant potential of EGISTs has to rely on the prognostic factors of GISTs, including size of tumor, frequent mitotic activity (2/50 HPF), high cellularity, mutation of KIT (exon 11), and coagulative necrosis.^3,9 In addition, specific locations of an EGIST must be considered in the prediction of its prognosis.

EGISTs are usually asymptomatic, depending on the location, size of the tumor, and lack of mucosal involvement.⁵ The usual clinical symptoms include abdominal pain, early satiety, ileus, bleeding, anemia, and weight loss.⁸ The current definitive treatment for GISTs, including EGISTs, is surgery. Adjuvant therapy appears to be warranted because of high recurrence rates despite complete resection.⁹ Imatinib mesylate, a specific inhibitor of KIT tyrosine kinase, is a current treatment of choice for advanced GISTs. It has also proven to be of benefit as adjuvant therapy with surgery to prevent recurrences.

This is the first known reported case of a giant pancreatic EGIST presenting with abdominal distension due to massive size of the tumor and hepatic encephalopathy secondary to hepatic metastasis and emphasizes the need for tissue diagnoses.