Hypervascular Gastric Masses: CT Findings and Clinical Correlates

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1 Gastrointestinal Imaging Review Johnson et al. CT of Hypervascular Gastric Masses Gastrointestinal Imaging Review Downloaded from by on 02/15/18 from IP address Copyright RRS. For personal use only; all rights reserved Pamela T. Johnson 1 Karen M. Horton Elliot K. Fishman Johnson PT, Horton KM, Fishman EK Keywords: CT, enhancement, gastric, multiplanar reconstruction, neoplasm DOI: /JR Received March 8, 2010; accepted after revision May 26, ll authors: The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Hospital, 601 N Caroline St., Room 3140D, altimore, MD ddress correspondence to P. T. Johnson (pjohnso5@jhmi.edu). WE This is a Web exclusive article. JR 2010; 195:W415 W X/10/1956 W415 merican Roentgen Ray Society Hypervascular Gastric Masses: CT Findings and Clinical Correlates OJECTIVE. This article focuses on masses that are hypervascular on IV contrastenhanced CT. CONCLUSION. The rising use of dual-phase IV contrast-enhanced CT will result in an increase in incidental detection of hypervascular gastric masses. Radiologists must be aware of the range of abnormalities that may appear as a hyperenhancing gastric mass because the differential diagnosis includes both benign and malignant lesions. N umerous articles have described the CT appearance of gastric masses, both benign and malignant. CT enables lesion characterization in terms of configuration, location within the gastric wall (Table 1), and enhancement pattern [1]. This article focuses on a subset of gastric abnormality: lesions that appear hypervascular on CT. We define hypervascular masses as those with mild, moderate, and marked hyperenhancement as opposed to lesions such as mucinous adenocarcinoma and lymphoma, which appear hypovascular on IV contrast-enhanced CT. Organized by anatomic location within the bowel wall, abnormalities are shown using a combination of axial images, 2D multiplanar reformations, and 3D volume rendering. CT Technique Many small hypervascular gastric lesions will be identified serendipitously. However, for dedicated CT of the stomach, protocol optimization includes narrow collimation, high quality IV contrast enhancement, and adequate gastric distention. Low-density oral contrast material is preferable to high-density agents, which may obscure visualization of enhancing lesions. We typically give water as oral contrast material because it is well tolerated and results in adequate distention of the stomach and duodenum. In some situations, glucagon may be useful to decrease peristalsis and improve distention, but we do not use it routinely. IV contrast administration is crucial to detect changes in gastric mural enhancement and small lesions. The literature supports the use of dual-phase imaging (arterial and venous acquisitions) for detection and staging of gastric malignancies [2, 3]; we typically use fixed delays of seconds for the arterial phase and 60 seconds for the venous phase. The early arterial acquisition in important for vascular mapping before surgery [4]. IV contrast material with a concentration of 350 mg I/mL is infused at 4 5 ml/s. Gastric lesions can be small and flat, necessitating the use of thin collimation (0.6-mm detector thickness, 3-mm section thickness for axial images, and mm sections for 3D postprocessing). Given the complex anatomy of the stomach, axial imaging alone is limited. Multiplanar reformations (MPRs) or 3D volume rendering are valuable for comprehensive visualization of the entire stomach [5, 6]. Pathology Mucosal Lesions Polyps Usually incidental findings, polyps are present in 2% of patients who undergo gastric endoscopy [7, 8]. The most common is the hyperplastic polyp (70%) (also called inflammatory polyp ), which arises in the setting of gastritis and is not a true neoplasm [7, 9]. Most patients are asymptomatic; however, presentation may include nausea, vomiting, heartburn, or gastrointestinal bleeding [8, 9]. These lesions can regress or increase in size over time [10]. Hyperplastic polyps (Fig. 1) are typically solitary (two thirds of cases) and under 1 cm in size [10]. Despite the traditional teaching that these are benign, research has elucidated that hyperplastic inflammatory polyps have JR:195, December 2010 W415

2 Johnson et al. Downloaded from by on 02/15/18 from IP address Copyright RRS. For personal use only; all rights reserved TLE 1: Site of Origin Within the Gastric Wall for Hypervascular Masses Location in Gastric Wall Mucosa Submucosa Muscularis Lesion Polyp Gastric adenocarcinoma Carcinoid Glomus tumor Metastases Varices Gastrointestinal stromal tumor Fig. 1 Two patients with gastric polyp., 75-year-old woman who presented with anemia; endoscopy disclosed 3-cm antral mass. Sessile enhancing mass (arrow) arising from mucosa of posterior wall of antrum is seen on axial image from IV contrast-enhanced CT. Pathology revealed 2.1-cm hyperplastic polyp., 68-year-old woman who was imaged with CT for hepatitis C surveillance. xial image from IV contrastenhanced CT shows approximately 2-cm polypoid enhancing lesion (arrow) in antrum of stomach. Differential diagnosis included gastrointestinal stromal tumor, carcinoid or glomus tumor, and less likely gastric carcinoma. Upper endoscopy was conducted, confirming 2-cm antral polyp with superficial ulceration and friable mucosa. t pathology, lesion was shown to be hyperplastic inflammatory polyp. Fig year-old woman with history of multiple endocrine neoplasia type 1 with elevated serum gastrin level from gastrinoma. and, xial image () from IV contrast-enhanced CT shows multiple thickened gastric folds with polypoid projections, particularly in antrum. Differential diagnosis includes marked hypertrophy of stomach with lobulations seen in setting of gastrinoma or polypoid gastric neoplasms. dditionally seen on axial section () are small hypervascular masses (arrows) in duodenal wall. Endoscopy showed more than 20 broad-based and pedunculated polyps in stomach and multiple small sessile duodenal polyps. Fundic gland polyps and oxyntic gland dilatation (reflective of hypergastrinemia as typically seen in patients with Zollinger-Ellison syndrome) accounted for findings in stomach; duodenal pathology was multiple foci of gastrinoma. malignant potential, particularly when larger than 2 cm in size [10]. s many as 3% have been found to harbor dysplasia or carcinoma [9]. In addition to an association with the size of the polyp, the risk of malignancy correlates with increasing patient age and location in the more distal stomach [11]. Furthermore, patients with hyperplastic polyps have an increased risk of developing cancer at another location within the stomach [8]. nother common benign gastric polypoid lesion is the fundic gland polyp. Histopathologically, the fundic polyp represents epithelium-lined cystically dilated glands. These may arise sporadically or in association with familial adenomatous polyposis [12] but have been increasing in prevalence owing to widespread use of proton pump inhibitor therapy [7]. Fundic gland polyps also develop in the setting of unopposed gastrin secretion, in which case they are often multiple (Fig. 2). Like hyperplastic polyps, these can regress. Patients with familial adenomatous polyposis have an increased risk that fundic gland polyps harbor dysplasia [10]. More common in countries where gastric cancer is endemic are adenomatous polyps [10]. These are associated with atrophic gastritis and intestinal metaplasia as well as familial adenomatous polyposis [10]. The antrum is the site of origin more commonly than the body. Often in the 3 4 cm range, these are typically larger than hyperplastic and fundic gland polyps [7, 10]. Gastric adenocarcinoma The appearance of gastric adenocarcinoma (Fig. 3) varies according to the size and stage of the tumor. However, enhancement is an important finding that aids in lesion detection both at presentation [2, 13] and in the postoperative stomach [14]. Careful inspection of the gastric wall is essential to identify small masses or subtle variation in the normal multilayered appearance [15]. Early gastric cancer may present as a hyperattenuating polypoid lesion with the submucosa intact, hyperenhancement of the thickened mucosa, or a mucosal defect [16]. Mucosal masses due to gastric carcinoma enhance during the late arterial phase, whereas the margin deep in relation to the tumor will peak in enhancement during the later contrast-enhanced acquisition [2]. This varies according to histology, with most non signet ring lesions appearing as enhancing masses (70% moderate enhancement, 15% strong enhancement) [17]. oth mucinous and signet ring tumors may be hypoenhancing [2, 16]. Postprocessing with MPR (Fig. 3) and virtual gastroscopy improves lesion detection, compared with the use of MPRs or axial sections alone [2]. However, the role of CT goes beyond lesion detection, particularly in the setting of gastric cancer, where determination of depth of invasion and identification of metastases are essential to guiding management [15]. CT has been shown to be accurate for delineating the degree of mural invasion (80 85%), particularly for involvement of the serosa (93%) [15]. Use of MPRs improved accuracy for depth of invasion from 73% to 89% in one study [2]. n area of future research in gastric cancer imaging is measurement of tumor vasculari- W416 JR:195, December 2010

3 CT of Hypervascular Gastric Masses Downloaded from by on 02/15/18 from IP address Copyright RRS. For personal use only; all rights reserved ty because pathologic studies have shown that microvessel count correlates with lymph node involvement, poor outcome, and recurrence in the form of liver metastases [18]. However, preliminary results using 64-MDCT did not produce measurable indicators of advanced disease. Using a 50-mL bolus of 300 mg I/mL IV contrast material infused at 6 ml/s, Yao et el [19] imaged gastric cancer in 58 patients 11 times over a period of 55 seconds. With this technique, the blood volume quantified to the normal stomach was significantly less than with gastric cancer. However, the degree of perfusion, peak enhancement, and blood volume did not correlate with tumor stage or lymph node involvement [19]. Fold thickening in the stomach that mimics adenocarcinoma can be caused by Helicobacter Pylori gastritis (Fig. 4). CT appearance may vary from circumferential thickening of the antrum, a small area of minimal focal wall thickening (most commonly in the antrum), or thickening of the posterior wall [20]. Submucosal Lesions Carcinoid The stomach is an unusual location for carcinoid tumor [21, 22]. Unlike other locations in the gastrointestinal tract, there Fig. 3 Two patients with gastric adenocarcinoma. and, 65-year-old woman with necrotic and friable polyp discovered on esophagogastroduodenoscopy. On CT, axial image () and coronal multiplanar reconstruction () show 1.4-cm soft-tissue nodule (arrow) that is mildly enhancing on early phase imaging. iopsy indicated adenocarcinoma submucosal in situ. C, 57-year-old woman who presented with weight loss, dyspepsia, early satiety, and dysphagia. xial image from IV contrast-enhanced CT shows diffuse wall thickening and hyperenhancement of thickened mucosa, compatible with tumor infiltration. Upper endoscopy revealed adenocarcinoma. Fig year-old woman with weight loss. and, xial image () and coronal volumerendered image () from IV contrast-enhanced CT show markedly thickened, mildly enhancing gastric folds, particularly in fundus and body. Considerations included lymphoma, unusual gastritis, and adenocarcinoma, or alternatively, findings could be seen in setting of Zollinger-Ellison syndrome. Pathology showed active chronic Helicobacter pylori gastritis and superficial necrosis suggestive of ischemia, as can be seen with nonsteroidal antiinflammatory drug use. are multiple variants of gastric carcinoid (Fig. 5). Types 1 and 2 have an indolent course, enlarging slowly, remaining stable, or regressing [21]. The third type may have a more aggressive course depending on tumor size. Type 1 is associated with atrophic gastritis and comprises 75 80% of cases [23]. In this case, multiple small hyperenhancing masses are seen, usually less than 1 cm and almost always less than 2 cm [22, 24]. Hosokawa et al. [25] followed patients with this type of carcinoid for between 1.5 and 10.8 years, reporting no change in polyp size or progression of disease beyond the stomach. The second type of carcinoid tumor includes those that arise in the setting of Zollinger- Ellison syndrome, especially patients with multiple endocrine neoplasia type 1 [26] (Fig. 5). The gastric wall is typically thickened. gain, there are typically multiple masses present but of variable size [21, 24]. One primary difference compared with the first category is that these may ulcerate and can metastasize. In addition to these two categories of gastric carcinoid that occur as the result of certain stimuli, carcinoids can arise sporadically in the stomach as they do in the remainder of the gastrointestinal tract. These are generally solitary [22]. In a study by instock et al. [24], sporadic carcinoids measured between 0.5 and 4.5 cm and were more common in men. Ulceration may be seen, and solitary carcinoid has a metastatic potential, particularly when the size exceeds 3 cm [24, 26]. Glomus tumor Included in the differential diagnosis of small, hypervascular gastric masses is the glomus tumor (Fig. 6). These are proliferations of glomus cells intertwined with gastric smooth muscle, encasing vascular channels [27, 28]. Mucosal ulceration is not rare (45%) [28]. The stomach is the most common gastrointestinal location [27, 29]. Glomus tumors can be asymptomatic; however, patients with gastric glomus tumors not uncommonly present with gastrointestinal bleeding or ulcerlike symptoms [28, 30]. series of 32 patients from the rmed Forces Institute of Pathology reported a female predominance (72%) [28]. lthough not absolute, the predilection for an antral location (often along the greater curvature) is apparent in a review of case reports [27, 29]. Glomus tumors of the stomach are usually benign, although rare malignant lesions have been reported with metastatic potential. Factors related to risk of malignancy include tumor size (5 cm or greater) and mitotic activity > 5 per 50 high power field [28]. C JR:195, December 2010 W417

4 Johnson et al. Downloaded from by on 02/15/18 from IP address Copyright RRS. For personal use only; all rights reserved CT characteristics include dense arterial enhancement, which can be peripheral nodular, incomplete, or uniform [27, 29, 30]. Uniform hypervascularity is seen during the venous phase, with persistent enhancement on delayed acquisitions [27, 29, 30]. Metastases Metastatic disease to the stomach is rare. Primary tumors most likely to involve the stomach include melanoma, breast, lung, and esophagus [31 33]. The differential diagnosis narrows if the lesion is hypervascular to include melanoma and renal cell carcinoma. Fig. 5 Two patients with carcinoid tumor., 59-year-old woman with multiple endocrine neoplasia type 1 and history of elevated gastrin and serotonin levels. xial image from IV contrast-enhanced CT shows mildly hypervascular thickened folds, particularly in gastric fundus. Endoscopy revealed extensive linear and nodular neuroendocrine hyperplasia (composed of gastrin and chromogranin-positive G cells), parietal cell hyperplasia in body of stomach, and well-differentiated gastric carcinoid tumorlets in stomach. Tiny carcinoid tumors in this setting are expected to follow indolent course. D, 41-year-old man who presented with weight loss. Endoscopy disclosed multiple gastric polyps and pathologically well-differentiated neuroendocrine carcinoma. lthough identified on axial image (), gastric mass (arrow, and C) is better visualized on coronal multiplanar reformation image (C) from IV contrastenhanced CT. Hypervascular metastasis (arrow, D) was identified in right lobe of liver (axial image). C s an isolated finding, renal cell carcinoma metastatic to the stomach (Fig. 7) is extremely rare [33, 34]. In fact, one study showed that patients with a history of renal cell carcinoma and a new gastric mass are more likely to have primary gastric cancer [31]. Gastric metastases due to renal cell carcinoma are typically identified years after the primary diagnosis (mean, 6.5 years) [31]. The imaging appearance of renal cell metastasis has been described as a submucosal mass or masses that may ulcerate. Occasionally metastatic disease is isolated to the stomach, but Fig year-old man with glomus tumor discovered incidentally during CT for renal calculus. This case shows importance of adequate gastric distention. and, On contrast-enhanced CT performed at outside hospital (), stomach was collapsed. However, on follow-up IV contrast-enhanced CT (), in which stomach was well distended with water, not only is mass (arrow) better visualized but also mucosa draping over lesion reveals submucosal location. D more commonly gastric metastases from renal cell carcinoma are the harbinger of widespread metastases, with 76% having additional sites of metastatic disease in one study [31]. The most common source of gastric metastases, melanoma, can also be a hypervascular tumor. Imaging findings include multiple small nodules (with or without ulceration) or larger isolated masses [35]. Varices Proper characterization of gastric and gastroesophageal varices is essential (Fig. 8). On an arterial phase acquisition, these appear as polypoid masses of soft-tissue densi- Fig year-old man with history of metastatic renal cell carcinoma. xial IV contrast-enhanced CT image shows hypervascular polyp (arrow) that had enlarged since previous examination 2 months earlier (not shown). Isolated metastases to stomach from renal cell carcinoma is extremely rare. t endoscopy, pedunculated 1.5-cm polypoid lesion in distal body of stomach was found; pathology revealed metastatic clear cell carcinoma. W418 JR:195, December 2010

5 CT of Hypervascular Gastric Masses Downloaded from by on 02/15/18 from IP address Copyright RRS. For personal use only; all rights reserved ty, mimicking solid masses. The venous phase acquisition is the key to making the correct diagnosis to prevent a potentially catastrophic biopsy [36]. The underlying causes are typically apparent on CT, including cirrhosis and other manifestations of portal hypertension or splenic vein occlusion (may be caused by pancreatic neoplasm or pancreatitis). When the splenic vein is occluded, the gastroepiploic vein coursing outside the greater curvature becomes enlarged. Fig year-old man with history of cryptogenic cirrhosis. and, xial arterial () and venous () images from IV contrast-enhanced CT show polypoid masses (arrows) in distal esophageal and gastric fundus, with soft-tissue attenuation on arterial acquisition. Venous phase imaging is key to show enhancement of varices. Fig year-old woman with hepatitis, being imaged to rule out liver mass. On venous phase coronal multiplanar reformation (MPR) image from IV contrast-enhanced CT, incidentally identified is cm mildly heterogeneous hypervascular mass (arrow) arising from gastric antrum. Exophytic configuration and location deep in relation to mucosa are well shown using coronal MPR. Pathology was epithelioid gastrointestinal stromal tumor. Muscularis The stomach is the most frequent location for gastrointestinal stromal tumors (GISTs), which most commonly originate from the muscularis within the gastric wall [37 40]. Overall, 60 70% arise from the stomach, with the small bowel the second most common location [39, 41]. Within the stomach, the body is a more common location than the antrum [40, 42]. The rate of malignancy correlates with the location, with lesions in the cardia or fundus more likely to be malignant or show progressive disease [40]. Most (70 80%) GISTs are nonmalignant [38]. enign GISTs may appear as small hypervascular masses, similar in appearance to carcinoid tumor [37, 43] (Fig. 9). In a series of malignant GISTs [38], the small bowel was the most common location (49/105, 47%), followed closely by the stomach (43/105, 41%). Malignant masses were large (mean size, 13 cm; usually > 5 cm) and often had central necrosis (67%) but remained well defined (86%). scites was an uncommon finding [38], and GISTs do not typically metastasize to lymph nodes [37]. Liver metastases can be hypervascular on late arterial phase acquisitions [37]. In a comparative study of benign and malignant lesions, findings associated with malignancy included size of the mass and presence of necrosis as well as identification of metastases [39]. oth the appearance of GIST and clinical manifestations vary according to size. Nishida et al. [40] evaluated 271 patients and found that larger masses were associated with bleeding and pain as well as the presence of necrosis at CT. They concluded that masses less than 3 cm are usually homogeneous, with necrosis characteristic of those greater than 6 cm. Pitfalls Occasionally, it can be difficult to determine the exact origin of a mass if it is contiguous with both stomach and liver or pancreas. n exophytic hepatic mass (Fig. 10) may be mistaken for an extraluminal gastric mass, in particular a GIST arising from the wall of the stomach. Multiplanar displays can be useful in aiding accurate localization of these masses. Conclusions The cases presented in this article show the range of gastric abnormalities that can appear as a hypervascular mass at CT. It is important to recognize that many of these lesions have a similar CT appearance. Once identified, consideration of CT findings (i.e., location within the gastric wall, configuration, degree of enhancement) and patient history may aid in narrowing diagnostic considerations because Fig year-old man with left upper quadrant mass incidentally discovered during workup for hematuria. and, xial image () from IV contrast-enhanced CT shows 7-cm exophytic soft-tissue density mass (arrow) with peripherally enhancing vascularity, extending from greater curvature of stomach superiorly, most consistent with diagnosis of gastrointestinal stromal tumor. Prominent vascularity was concerning for malignancy. Surgical resection disclosed exophytic cavernous hemangioma of liver subtle connection (arrowheads) identified retrospectively on coronal volume-rendered image () mimicking mass (M) of gastric origin. JR:195, December 2010 W419

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