Gastric adenomyoma in children: A case report

Abstract

BACKGROUND

Gastric adenomyoma (GA) in children is a relatively rare condition, and currently, there is limited knowledge regarding its optimal diagnostic methods and treatment strategies. To improve our understanding GA particularly in children, one case of a 4-month-old boy was reported and existing literature was comprehensively reviewed.

CASE SUMMARY

A 4-month-old boy was admitted to the hospital with a 2-month history of recurrent vomiting of gastric contents. 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. Pathological finding showed that a mass approximately 2.8 cm × 2 cm × 1.5 cm in size and grayish-white in color was detected. 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 low.

CONCLUSION

We report a case of GA in children, successfully treated with laparoscopic surgery. Ultrasound and computed tomography may be helpful in differential diagnosis when detecting low-density septal lesions biased toward one side. We also review the existing literature data regarding GA in children.

Key Words: Gastric adenomyoma; Children; Differential diagnosis; Pathology; Surgery; Case report

Core Tip: The article reported one case of gastric adenomyoma in an infant who was primarily diagnosed with pyloric hypertrophy. We reviewed reported cases and found that gastric adenomyoma was frequently misdiagnosed as other diseases like duplication cyst. Presence of heterogeneous echo in ultrasound and cystic appearance in computed tomography were helpful for differentiating preoperatively. These findings could provide valuable reference for surgeons to improve the preoperative diagnostic accuracy.

INTRODUCTION

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.

CASE PRESENTATION

Chief complaints

A 4-month-old boy was admitted to the hospital with a 2-month history of recurrent vomiting of gastric contents.

History of present illness

The symptoms of vomiting began 2 months ago.

History of past illness

There is no history of past illness.

Personal and family history

There is no personal and family history.

Physical examination

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.

Laboratory examinations

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.

Imaging examinations

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.

Figure 1 Ultrasound findings of pyloric canal (left) and upper gastroenterography (right). The arrow indicates the mass that deviated the pyloric duct to one side.

Figure 2 Laparoscopic surgery. “a” represents stomach and the orange arrow indicates the mass in the pyloric region.

FINAL DIAGNOSIS

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).

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.

TREATMENT

A pyloric canal resection and gastroduodenal anastomosis were performed.

OUTCOME AND FOLLOW-UP

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

DISCUSSION

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].

Table 1 Cases of gastric adenomyoma in children.

Ref.	Gender	Age	Symptoms	Imaging	Preoperative diagnosis	Surgery
Moiseenko[9], 1964	Female	5 months old	Esophageal reflux	Barium swallow indicated esophageal reflux	Esophageal reflux	Nissen fundoplication and mass excision
Takeyama et al[16], 2007	Female	1 month old	Intermittent vomiting free of bile of one week	US demonstrated heterogeneous intramural mass of the pyloric region	Hypertrophic pyloric stenosis	Lesion excision
Min et al[2], 2012	Female	5 years old	Intermittent epigastric pain, vomiting, poor oral intake, irritability, and fever	US and CT demonstrated a thick-walled cystic lesion; UGI showed an extrinsic mass with a lobulated contour without evidence of perforation	Gastric duplication cyst	Distal gastrectomy with gastroduodenostomy
Castain and Rullier[10], 2012	Female	4 months old	Vomiting, weight loss, and abdominal pain	US showed a non-circumscribed heterogeneous mass of the pyloric wall with microcystic features	Hypertrophic pyloric stenosis	Pyloric junction removal
Rhim et al[17], 2013	Male	1 week old	Persistent vomiting	US showed asymmetrical submucosal thickening of the anterior wall of the pylorus and the lesion protruded into both luminal and serosal sides; UGI showed elongation and narrowing of the pyloric canal and shouldering of the antrum	Gastric outlet obstruction	Billroth I anastomosis
Aljahdali et al[11], 2012	Male	13 days old	Progressive nonbilious vomiting	US demonstrated a hyperechoic intramural pyloric mass	Pyloric stenosis	Mass dissection and Graham patch repair
Oviedo Gutiérrez et al[19], 2015	Female	49 days old	Nonbilious vomiting of 48 hours	US showed a nonobstructive nodular lesion in the anterior pyloric wall; MRI suggested a myofibroblastic tumor	Hypertrophic pyloric stenosis	Complete resection of the pyloric tumor
Arslan et al[20], 2018	Female	5 years old	Abdominal pain, poor oral intake, and fever	US showed an intramural hypoechoic heterogeneous nodular mass; CT revealed a cystic lesion	Gastric duplication cyst	Mass excision, double-layer transverse anastomosis
Kamrani et al[18], 2019	Female	15 years old	Nausea and vomiting over a period of two years	CT showed a circumferential prepyloric mass; EGD showed the distal antrum and proximal pylorus contained a frond-like circumferential nearly obstructing submucosal mass	Gastric duplication cyst	Distal gastrectomy with gastroduodenostomy

US: Ultrasound; CT: Computed tomography; UGI: Upper gastrointestinal series; MRI: Magnetic resonance imaging; EGD: Esophagogastroduodenoscopy.

CONCLUSION

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.