Gastric adenomyoma in children: A case report.

A 4-month-old boy was admitted to the hospital with a 2-month history of recurrent vomiting of gastric contents. The symptoms of vomiting began 2 months ago. There is no history of past illness. There is no personal and family history. He was in good nutritional status with a weight of 7.3 kg and a height of 66 cm. The child did not present with pallor or cyanosis of the skin and the abdomen was soft, with no palpable mass. A mass approximately 2.8 cm × 2 cm × 1.5 cm in size and grayish-white in color was detected. An incision was made and a 1.2 cm × 1.2 cm × 0.7 cm cystic cavity was observed. The cystic wall was composed of smooth muscles lined with the gastric mucosal epithelium and a small amount of intestinal epithelium. Scattered glandular epithelium and a small amount of pancreatic tissue were observed in smooth muscle. Immunohistochemistry revealed positivity for gastrin, insulin, and smooth muscle actin, confirming the diagnosis of GA. In addition, the Ki-67 proliferation index was only 5%, indicating that the tumor had low malignant potential. Ultrasound examination demonstrated that the pyloric canal muscle was 3.2 mm in thickness, 14.6 mm in diameter, and 17.6 mm in length. Upper gastrointestinal tract angiography (Figure 1 ) revealed elongation of the pyloric canal, with slow passage of barium. The preoperative diagnosis was congenital hypertrophic pyloric stenosis. During laparoscopic surgery, a mass was noted on the anterior wall of the pylorus and compression of the mass caused pyloric canal stenosis (Figure 2 ). Intraoperative frozen section examination suggested the possibility of GA. Ultrasound findings of pyloric canal (left) and upper gastroenterography (right). The arrow indicates the mass that deviated the pyloric duct to one side. Laparoscopic surgery. “a” represents stomach and the orange arrow indicates the mass in the pyloric region.

The patient’s symptoms, as well as upper gastrointestinal tract angiography and ultrasound, initially suggested a diagnosis of congenital hypertrophic pylorus, which was invalidated during the operation when a mass was observed in the pyloric region. Postoperative pathological examination confirmed the presence of GA. Immunohistochemistry was positive for gastrin, insulin, and smooth muscle actin, confirming the diagnosis of GA. Additionally, the Ki-67 proliferation index was very low, at approximately 5% (Figure 3 ). Pathology images for gastric adenomyoma. A: Hematoxylin and eosin staining, “a” represents intestinal epithelium and “b” indicates ectopic pancreas; B: Representative immunohistochemical staining images of gastrin-positive sections: Gastrin; C: Insulin; D: Smooth muscle actin; E: Ki-67 staining.

The diet was gradually resumed 4 days postoperatively. The patient recovered well and was subsequently discharged from the hospital.

A pyloric canal resection and gastroduodenal anastomosis were performed.

Children with GA mainly present with vomiting symptoms similar to those in congenital hypertrophic pyloric stenosis or gastric duplication. Ultrasound and CT can detect low-density septal lesions in the pylorus, which are biased toward one side, and may be helpful in diagnosis. Currently, radical resection is the preferred treatment modality in children.

GA is a rare benign tumor composed of smooth muscle, duct, and glandular structures. However, controversy exists regarding the pathological nomenclature and classification of GA. Some studies suggest that GA should be classified as type III ectopic pancreas pathologically[ 1 ], given that the pathological characteristics of GA are similar to those of type III ectopic pancreas, including glands with clear capsules and corresponding duct structures. Most scholars believe that smooth muscle hyperplasia associated with GA is not a simple reactive change caused by epithelial displacement but a hamartoma containing incompletely differentiated pancreatic tissue components[ 2 ]. Therefore, GA is occasionally referred to as adenomyoma, myoepithelial hamartoma, adenomyoma hamartoma, adenomyomatous hamartoma, or adenomyosis. GA and type III ectopic pancreas have been reported to coexist[ 3 ]. Currently, some imaging findings can help distinguish GA from other lesions. For instance, GA is often localized to the pylorus on ultrasound and presents with uneven or nodular changes. In the present case reported in this article, ultrasonography revealed that the mass was biased toward the pylorus. The ultrasound image of congenital hypertrophic pyloric stenosis demonstrated a strong echo band (mucosal layer) in the center surrounded by a thickened, uniform, low-echo muscle layer. On computed tomography (CT) scans, GA is characterized by low-density cystic lesions with enhanced diaphragms composed of glandular or fibrous tissue, whereas congenital hypertrophic pyloric stenosis is characterized by soft tissue density around the pylorus[ 4 ]. If ectopic gastric mucosa in a gastric duplication is present, the cyst may exhibit an enhanced appearance. However, distinguishing GA from gastric stromal tumors using preoperative imaging is challenging. Endoscopic ultrasound examination allows doctors to view the internal structure of the mass clearly and determine its specific location[ 5 ]. Endoscopic ultrasound-guided fine-needle aspiration can be used for early histological diagnosis of masses larger than 2 cm in diameter before surgical resection[ 6 , 7 ]. However, due to the large diameter of the ultrasound endoscope, performing this operation on young infants can be challenging. The radical cure for GA is surgical resection through the gastroduodenal anastomosis (Billroth I procedure). As lesions in children are usually small, gastroduodenal anastomosis can be performed in a single stage after complete resection of the tumor, which is beneficial for reducing the risk of recurrence. Endoscopic submucosal dissection (ESD) is a surgical technique that has garnered attention over the last two decades. A single-center retrospective study analyzed more than 500 patients who underwent ESD over 7 years and discovered that the postoperative pathology in 15 patients with a mean age of 46 years demonstrated GA[ 8 ]. Among them, 14 were located in the gastric submucosa and one in the superficial muscle layer of the gastric wall. The tumor diameter was less than 3 cm, and all tumors were successfully removed without obvious recurrence or metastasis within 1-5 years. We recommend that all patients undergo endoscopic examinations to evaluate the feasibility of ESD. Preoperative endoscopic ultrasound microprobe examination can aid in determining the location of lesions in the gastric wall. However, GA in children may involve the muscular or submucosal layer and due to the thin gastric wall, the adenomyoma tends to be relatively large. Currently, no reports focus on children undergoing ESD for the management of this condition. GA is generally a benign lesion; however, some studies have suggested that it may be associated with tumors or malignant transformations. Although no cases of recurrence after resection have been reported, documented cases of GA coexisting with gastric adenocarcinoma are available[ 9 - 11 ]. Ng et al [ 12 ] reported on an eight-week-old infant with symptoms of intestinal obstruction accompanied by pseudomyxoma peritonei. Therefore, once a child is diagnosed with GA, the scope of the examination should be expanded appropriately. To further explore patient characteristics, management considerations, and outcome in patients with GA, PubMed and Embase databases were searched using the search term “gastric adenomyoma” until December 2024. All article types published between 1960 and 2024 were included. The language or location was not limited, and each relevant text was thoroughly reviewed and examined. Cases were excluded from the analysis if the full paper was inaccessible, if the article was not a case report or case series, or if the article did not report on pediatric patients. Diagnosis of GA was based on pathological evidence. Relevant information, including author, year of publication, basic case information (number of cases and age), pathology, surgical conditions, and postoperative follow-up, was extracted from the literature. This study did not require approval from an ethics committee. Nine relevant articles were included, encompassing seven female and two male patients, with a mean age of 34 months (1 week to 15 years). Moreover, the median age in the study was 4 months. Vomiting was the most frequently reported clinical manifestation in seven out of nine cases. One patient presented with the symptom of gastroesophageal reflux. Other non-specific symptoms included abdominal pain, fever, poor food intake, and weight loss. Preoperative physical examinations and laboratory tests revealed no abnormal results. Ultrasound was the principal diagnostic imaging modality and revealed the presence of a heterogeneous mass or cystic lesion within the pyloric wall in eight cases. Regarding upper gastrointestinal tract angiography, two patients exhibited gastric outlet obstruction, and one patient suggested gastroesophageal reflux. CT scans (2 out of 9) detected cystic masses in the pylorus, but in one case, the magnetic resonance findings demonstrated inflammatory myofibroblasts. Considering age, symptoms, and auxiliary examinations, the preoperative diagnoses were congenital pyloric hypertrophy (3/9), gastric duplication cyst (3/9), pyloric stenosis (2/9), and gastroesophageal reflux (1/9). Notably, none of the preoperative and postoperative diagnoses were consistent. Surgical exploration was performed in all nine cases. During surgery, masses with an average diameter of 19 mm were detected in the gastric pylorus. The surgical procedures adopted were partial pylorectomy in one case, distal gastrectomy combined with gastroduodenostomy in three cases, lesion resection (unspecified surgical details) in three cases, mass dissection and patch repair in one case, and pyloric junction resection in one case. Pathological examination demonstrated that the mass was composed of glands and smooth muscles with infiltrating inflammatory cells. However, an ectopic pancreas was only identified in four cases. No studies reported any postoperative complications or recurrence. To date, no more than 60 cases of GA have been reported in children or adults[ 1 ]. The age of onset ranged from 1 week to 82 years, with the main age group being 40-60 years old[ 5 ]. Approximately 90% of GA cases occur in the gastric antrum[ 13 ]. The clinical manifestations of GA depend on the location, extent, and depth of the lesion infiltration. GA in adults usually presents with nonspecific clinical symptoms, including nausea, vomiting, abdominal pain, with occasional hematemesis, melena, and even secondary perforation peritonitis[ 14 , 15 ]. In pediatric cases, vomiting is the main clinical symptom (Table 1 ), which is often misdiagnosed as other conditions that may cause gastric outlet obstruction: Hypertrophic pyloric stenosis, gastric duplication malformation, or gastric tumor[ 2 , 16 - 18 ]. The main treatment method was still surgical removal of the mass and reconstruction of the digestive tract. Table 1 summaries some cases of gastric adenomyoma in children[ 2 , 9 - 11 , 16 - 20 ]. Cases of gastric adenomyoma in children US: Ultrasound; CT: Computed tomography; UGI: Upper gastrointestinal series; MRI: Magnetic resonance imaging; EGD: Esophagogastroduodenoscopy.

Gastric adenomyoma (GA) is rare, with an especially low incidence in pediatric patients, making it a relatively unfamiliar entity in pediatric gastroenterology. Differentiating GA from lesions such as pyloric hypertrophy before surgery can be difficult because clinical manifestations and imaging features of GA often overlap with others. Therefore, GA can be easily misdiagnosed. This article reports a case of infantile GA and thoroughly examined the clinical course, diagnostic work-up, and treatment outcomes. It also provides a detailed literature review with the aim of improving the understanding of this disease in the pediatric population.