Utility of Follow-Up Computed Tomography (CT) and Fluorodeoxyglucose-Positron Emission Tomography/CT (FDG-PET/CT) in Diagnosing Gastrointestinal Stromal Tumor (GIST) Presenting as Spontaneous Hemoperitoneum: A Case Report.

A 76-year-old Japanese man with sudden epigastric pain was admitted to a local hospital. The patient was referred for a 10 cm space-occupying lesion and ascites on ultrasonography (US). He had no history of trauma. However, the patient had a history of atrial fibrillation and was prescribed rivaroxaban. Upon arrival at our hospital, the patient was conscious, and vital signs showed a heart rate of 98 bpm and atrial fibrillation, with a blood pressure of 123/67 mmHg. The patient experienced intermittent diffuse abdominal pain, nausea, and abdominal fullness. A head-sized mass with a smooth surface and good mobility was palpable in the mid-abdomen. Laboratory studies showed a low hemoglobin level of 10.7 g/dL, a white blood cell count of 5350/μL, a platelet count of 24.7×104/μL, an international normalized ratio of prothrombin time of 1.76, an activated partial thromboplastin time of 44.5 seconds, and a C-reactive protein level of 1.15 mg/dL. CT revealed a 100×150 mm mass consisting of heterogeneously enhanced solid and giant cystic lesions and ascites (Figure 1 ). However, we were unable to identify the source of the bleeding. The patient's vital signs were stable, and he opted for a conservative treatment. Although the hematoma size had not changed on US since admission, the patient's abdominal pain improved, and he was subsequently discharged after nine days. (A) The axial view showed a huge mass consisting of heterogeneously enhanced solid and giant cystic lesions. (B) The coronal view showed a 100×150 mm mass. CT: computed tomography Two months later, a contrast-enhanced CT scan showed that the size of the hematoma had not changed; however, a part of the caudal side of the hematoma had a high-density area that had not been observed before (Figure 2 ). Therefore, we suspected that the hematoma was caused by malignancy. Subsequently, we conducted FDG-PET/CT, which revealed FDG accumulation in that area (Figure 3 ). A spontaneous hematoma due to malignancy was strongly suspected, and the patient underwent exploratory laparotomy. Laparotomy revealed a large encapsulated mass (approximately 15 cm) arising from the greater omentum that adhered to the transverse colon and pylorus. Thus, an upper midline incision was made, and a combined resection of the adjacent organs was performed. Gross examination showed a globular soft tissue mass measuring 12.8×11×10 cm (Figure 4 ). The cut surface of the specimen was a hematoma. Histopathological examination revealed that the tumors consisted of proliferating spindle cells with massive necrosis (Figure 5A ) and 16 mitoses per 50 consecutive high-power fields. Immunohistochemical examination revealed the expression of KIT (CD117) (Figure 5B ) and was negative for CD34 (Figure 5C ). Therefore, we made a diagnosis of high-risk extraluminal gastric GIST. The patient was discharged nine days after the operation and treated with imatinib mesylate. Two years after surgery, he presented to our hospital complaining of sudden epigastric pain. An abdominal CT scan revealed peritoneal metastasis and hemoperitoneum. The patient is currently undergoing palliative treatment. (A) Admission date. (B) Day 1. (C) Two months later. A part of the caudal side of the hematoma had a high-density area that had not been seen before (yellow circle). CT: computed tomography (A) Axial view. (B) Coronal view. FDG-PET/CT: fluorodeoxyglucose-positron emission tomography/computed tomography (A) Gross examination shows a globular soft tissue mass measuring 12.8×11×10 cm. (B) The cut surface of the specimen was a hematoma. (A) Microscopic examination (hematoxylin-eosin staining, original magnification: 200×) showed proliferation of spindle cells. Immunohistochemical staining revealed that tumor cells were positive for c-kit (B) and negative for CD34 (C).

Spontaneous hemoperitoneum is a rare and potentially life-threatening condition [ 1 ]. Gastrointestinal stromal tumor (GIST) can present as spontaneous hemoperitoneum [ 2 ]. Owing to their rarity, the diagnosis of GIST as the cause of hemoperitoneum may be challenging. Very few imaging follow-ups have been performed. Herein, we present a case in which follow-up computed tomography (CT) and fluorodeoxyglucose-positron emission tomography/CT (FDG-PET/CT) were useful for confirming the presence of GIST.

Spontaneous hemoperitoneum is a rare and potentially life-threatening condition with a wide range of differential diagnoses (Table 1 ) [ 1 ]. GIST can present as spontaneous hemoperitoneum [ 2 ]. This case suggests that intraperitoneal hematomas from GIST have the following two characteristics: When an unexplained intraperitoneal hematoma is identified, follow-up CT and FDG-PET/CT are useful for identifying the presence of GIST, and surgical intervention is recommended to identify the causes. GIST: gastrointestinal stromal tumor First, we must be aware that GIST can be a cause of sudden intra-abdominal hemorrhage or hematoma. Additionally, follow-up CT and FDG-PET/CT are useful for determining the presence of malignant tumors. Therefore, we searched for previous reports on intraperitoneal hemorrhage caused by GIST in the PubMed database using the keywords "intraperitoneal hemorrhage, bleeding, or hematoma" and "GIST" and reviewed 24 cases. Most cases required emergency surgery, and very few cases required follow-up imaging. Typically, an intraperitoneal hematoma gradually becomes smaller as it is absorbed by the body, and the CT appearance of a hematoma can change from initial enhancement to non-enhancement as it resolves. However, we found that intraperitoneal hematomas from GIST have two characteristics. First, an intraperitoneal hematoma from a GIST does not become smaller because it is formed by a tumor. Second, the tumor becomes apparent over time. At the initial presentation, the relatively high density of the hematoma on CT was similar to that of the tumor, making the tumor not apparent. Gradually, as the hematoma density decreased, the tumor became apparent. In the present case, these findings were observed, and a tumor was suspected. FDG-PET/CT revealed FDG accumulation in that area. Thus, follow-up CT and FDG-PET/CT are useful for identifying the presence of GIST. Second, surgical resection should be performed to identify the cause of spontaneous intraperitoneal hematoma when the cause is unclear. In previous reports on GIST, most patients with intraperitoneal bleeding from GIST had abdominal pain and hematoma on CT findings. These symptoms are similar to those of idiopathic omental bleeding [ 3 ]. Some previous reports on idiopathic omental bleeding have recommended conservative treatment, and in recent years, minimally invasive treatments, such as transcatheter arterial embolization (TAE) for idiopathic omental bleeding, have been reported and are preferred [ 4 - 6 ]. In cases of GIST, complete surgical resection is the only potentially curative treatment. Distinguishing between these conditions can be challenging because of their overlapping clinical features. Thus, surgical resection should be performed to identify the cause of spontaneous intraperitoneal hematoma. Table 2 lists the previous reports of intraperitoneal hemorrhage caused by GIST. GIST: gastrointestinal stromal tumor

This case report indicates that contrast-enhanced follow-up CT and FDG-PET/CT are useful for detecting the presence of GIST when faced with an unexplained intraperitoneal hematoma. These imaging modalities can help to differentiate between hematomas caused by benign conditions and those caused by malignant tumors, such as GIST. Furthermore, when the cause of a spontaneous intraperitoneal hematoma is unclear, surgical intervention is recommended to identify the underlying pathology. Future studies could contribute to standardizing the approach for spontaneous hematoma formation in GIST.