Idiopathic Hypertrophic Pyloric Stenosis in an Adult, a Potential Mimic of Gastric Carcinoma

Abstract

Primary or idiopathic hypertrophy of the pyloric muscle (IHPM) is a rare entity with uncertain pathogenesis which both clinically and pathologically mimics gastric cancer. We present a rare late-occurring case of IHPM in a 71-year-old Caucasian man with no apparent predisposing factor. Imaging studies demonstrated gastric distension with air fluid levels and no evidence of extrinsic compression. At upper endoscopy, massive gastric distension and no evidence of any ulcer or other mucosal defects were observed. Microscopically, marked hypertrophy of muscularis mucosa with smooth muscle cells arranged in whorls and fascicles was present which gradually transitioned to normal areas. The muscle fibers stained with smooth muscle actin and trichrome stain highlighted fibrosis between the muscle fibers. Although uncommon, IHPM can clinically and histologically mimic other proliferations in the gastric wall, such as gastrointestinal stromal tumor or a spindle cell neoplasm. The recent advances in understanding the pathogenesis of IHPM are discussed.

Adult Idiopathic Hypertrophic Pyloric Stenosis

“…In a case report Zarineh et al 1 stratified the etiological classification of adult idiopathic hypertrophic pyloric stenosis to two main types: primary, which has no underlying pathology, and secondary, which may encompass several causes, including healing of a previous gastric or duodenal ulcer, cancer, postoperative adhesions, and vagus nerve hyperactivity, ultimately leading to hypertrophy of the muscular anatomy. 1,3,7,9,10 In another report, Danikas and colleagues 5 stratified AIHPS to three types. Type 1 was described as a late-stage, infantile, hypertrophic pyloric stenosis.…”

“…1 The literature reports that congenital pyloric stenosis is estimated to have an incidence of 0.2% to 0.5% of all live births. [1][2][3][4] Jean Cruveilhier is thought to be the first to describe AIHPS (in 1835). 5 The most common clinical symptom is abdominal distention relieved by vomiting.…”

Adult idiopathic hypertrophic pyloric stenosis - a common presentation with an uncommon diagnosis

“…The most universally accepted classifications are by Danikas et al and Zarineh et al Danikas et al divided HPS into three types: Type 1, which is infantile HPS diagnosed at a late stage; Type 2, which is the most common type, and which occurs during adult life and is likely secondary to underlying GI pathologies, such as peptic ulcer disease, malignancy, and certain inflammatory diseases; and Type 3, which is idiopathic HPS of adult onset [9]. Zarineh et al divided HPS into primary, which has no underlying cause and under which AIHPS would be classified, and secondary, caused by an underlying disorder like the excessive healing of gastric or duodenal ulcers, malignancy, GISTs, postoperative intraabdominal adhesions, bezoars, and increased vagal activity causing pylorus hypertrophy [10]. The secondary type of HPS has no or mild hypertrophy of the pylorus muscle as compared to the primary type.…”

“…However, it still seems unclear as to the reason of the prolonged asymptomatic period until the age of 30–60 years. Some researchers postulate edema, spasm, or inflammation triggers pyloric occlusion in a predisposed individual [10]. Other possible etiologies include protracted pylorospasm, vagal hyperactivity, and changes in Auerbach’s plexus.…”

“…Currently, there is no evidence of one surgical technique being superior to another. Further research on AIHPS is warranted before a method can be finalized as the standard of care [10,13,21]. …”