Endosonographic Features of Gastric Adenomyoma, a Type of Ectopic Pancreas

We read with great interest the article by Chu [1] on an endoscopic ultrasound (EUS) appearance of gastric adenomyoma. He described for the first time the EUS appearance in a case of a 1.5 cm submucosal nodule in the gastric antrum. EUS showed that the nodule was related to the submucosa (the third echo layer), with a cystic center lined with a hyperechoic rim. After the nodule was resected laparoscopically, the resected specimen revealed features of adenomyoma.

Histologically, ectopic pancreas is composed of normal pancreatic acini and ducts, with occasional islets. When smooth muscle and duct-like structures are the only components, the term adenomyoma has been used [2] [3]. Thus, adenomyomas are considered to represent ectopic pancreas without exocrine or endocrine components [2] [3] [4]. Heinrich classified ectopic pancreas into three histological types [5]: type I, with all elements of normal pancreatic tissue; type II, pancreatic tissue without islets; and type III, pancreatic ducts only. Adenomyoma is therefore Heinrich type III.

Despite Chu’s claim to be presenting the first description of the EUS appearance of gastric adenomyoma [1], we previously described the EUS features in two patients with gastric adenomyoma - ectopic pancreas of Heinrich type III - and compared the EUS images with resected specimens [6]. In our study of 10 patients with ectopic pancreas, the EUS appearance of ectopic pancreas was characterized by an indistinct margin, heterogeneous appearance, and location within either the third and fourth echo layers (fusion type), or only in the third echo layer (separate type). These findings correlated very closely with the histological findings. The lobular structure of the acinous tissue produced the indistinct margin pattern. The mainly hypoechoic image (acinous tissue) accompanied by scattered small hyperechoic areas (adipose tissue) contributed to the heterogeneous appearance. A small anechoic area (duct dilatation) and thickening of the fourth echo layer (muscular hypertrophy) were commonly visualized. All lesions of the fusion type were Heinrich type I; the separate type were Heinrich type II or III lesions. The EUS appearances of Chu’s lesion were consistent with our reported EUS features of the separate type without hypoechoic image (acinous tissue).

Most patients with ectopic pancreas are asymptomatic [7] [8] [9] [10] [11], but nonspecific gastrointestinal symptoms associated with pancreatitis [10] [11] [12] [13], cyst formation [7] [10] [14], jaundice [7], abscess formation [9], gastric outlet obstruction [10] [15], or malignant change [16] [17] have been described. Symptomatic ectopic pancreas should therefore be resected [6] [8] [10] [15] [18]. We believe that endoscopic removal of adenomyoma is a better treatment than the laparoscopic resection that was performed in the case reported by Chu, because of its minimal invasiveness and satisfactory postoperative results [6] [18] [19]. EUS provides the most useful information regarding tumor location in the gastric wall, and selects good candidates for endoscopic removal [6] [11] [18] [20]. The EUS image showed that Chu’s lesion was located in the submucosa separate from the muscularis propria - information that allows endoscopic removal of the lesion without major complications.

References

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