An association of hypertrophic pyloric stenosis and pyloric inflammatory myofibroblastic tumor-like lesion: A rare case of an infant with gastric outlet obstruction

We report a 1-month-old male infant with an association of hypertrophic pyloric stenosis (HPS) and inflammatory myofibroblastic tumor (IMT)-like lesion at the pylorus. The infant exhibited vomiting at a postgestational age of 17 days, and was diagnosed with HPS. Pyloric ultrasound showed anterior wall thickness of 10 mm and posterior wall thickness of 5 mm. Medical treatment could not relieve his symptoms, so an operation was performed. Pyloric muscle hypertrophy and a small tumor-like lesion at the pyloric anterior serosa were found. The tumor-like lesion was enucleated, and pyloromyotomy was performed. Histological examination during the operation indicated IMT-like lesion, although the suggestion of a histological diagnosis of IMT continued subsequently. Endoscopic biopsy for pre-pyloric mucosa showed eosinophilic gastritis. The postoperative course was uneventful. On an ultrasound 6 months after the operation, the muscle hypertrophy had disappeared and no tumor lesion was found. The symptoms of our patient could have been derived from muscle hypertrophy, which was induced by HPS and aggravated by IMT-like lesion and eosinophilic gastritis. Eosinophilic gastritis can also be related to the pathogenesis of IMT-like lesion.