TEACHING CASE
Adenocarcinoma arising in gastric inverted hyperplastic polyp: A case report and review of the literature

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Abstract

A 54-year-old man, found to have a submucosal tumor in the stomach by double contrast roentgenography, endoscopy, and endoscopic ultrasonography, underwent a laparoscopic partial gastrectomy. The pathological examination revealed that the lesion, measuring 45 mm×35 mm, was an inverted hyperplastic polyp (IHP) located in the submucosal layer and consisting mostly of columnar cells resembling foveolar epithelium and pyloric gland cells. Notably, adenocarcinoma with adjacent dysplasia was observed in the submucosal glands. Transition from hyperplasia to dysplasia and from dysplasia to adenocarcinoma was noted. The adenocarcinoma component was intensely and diffusely positive for p53 overexpression, while the dysplasia component showed only weak and focal positivity, suggesting a role of p53 mutation in the dysplasia–carcinoma sequence. Gastric IHP is very rare, and only 31 cases (in 29 patients) have been reported. Five of these IHPs coexisted with gastric adenocarcinomas, which had all developed separately from the IHP lesions. Therefore, this is the first case of adenocarcinoma arising within gastric IHP itself.

Introduction

Gastric inverted hyperplastic polyp (IHP), a rare type of gastric polyp, is characterized by downward growth of hyperplastic mucosa into the submucosal layer, usually resembling a submucosal tumor macroscopically [8]. This lesion has previously been described as hamartomatous polyp [4], [5], [10], [14], [15], [16], [17], hamartoma mimicking a submucosal tumor [9], submucosal heterotopia [11], and hamartomatous inverted polyp [13]. The lesion is now termed IHP because of the similarity to its colonic counterpart [8], [12].

Histologically, gastric IHP consists of overlying gastric mucosa and submucosal components, such as proliferating pseudo-pyloric glands, cystic glands, and bundles of smooth muscle. Fundic-type glands, intestinal metaplasia, and neuroendocrine cells can also be present. A total of 31 cases of gastric IHP (in 29 patients) have previously been reported, five of which (16.1%) coexisted with gastric adenocarcinoma [1], [17]. IHP and adenocarcinoma developed separately in all five cases.

Here, we present the first case of adenocarcinoma arising in a gastric IHP and review the previously reported gastric IHP with regard to gastric cancer.

Section snippets

Materials and methods

All specimens were fixed in 10%-buffered formalin and routinely processed. The paraffin-embedded tissue was investigated immunohistochemically using the avidin–biotin complex method for antibodies against MIB1 (DAKO, undiluted) and p53 (CM-1; Novocastra, 1:2000). An antibody against MIB1 recognizes Ki-67 antigen in the nucleus. Adequate positive and negative controls for a respective antibody were mounted on the same slide as the specimen.

Case report

A 54-year-old man, without any particular past or family history, was admitted to Kobe University Hospital for investigation of a submucosal tumor in the stomach. On admission, the physical examination and laboratory data were unremarkable. Double contrast roentgenography revealed a protruding lesion, 4 cm in size, in the anterior wall of the gastric antrum (Fig. 1A). Endoscopic examination also demonstrated a pedunculated lesion that was covered with normal gastric mucosa and that had a small

Histological features

The resected mass, measuring 45 mm×35 mm, was a well-circumscribed, protruding lesion covered with normal gastric mucosa. There was a small dell near its summit. A cross-section revealed a well-demarcated, white tumor with a slit-shaped internal cavity beginning at the dell (Fig. 2A). Microscopically, the lesion was located in the submucosa and was covered with normal gastric mucosa and muscularis mucosae. The muscularis mucosae was interrupted around the dell. The submucosal lesion consisted

Discussion

Gastric IHP is very rare, and only 32 cases (in 30 patients), including the present case, have been reported. The patients were between 8 and 81 years old (average 55.6±18.1), the male:female ratio was 14:16. Fifteen of the 32 gastric IHPs were located in the fornix and 12 in the body of the stomach; only five cases were observed in the antrum. Therefore, gastric IHP seemed to develop preferentially in the upper half of the stomach. The size of the lesion varied from <1 to>11 cm, and six of the

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