[745] Gastric Chief Cell Adenomas: Proposal for a New Entity

Stuti Shroff, Melissa Taggart, Asif Rashid, Taofic Mounajjed, Tsung-Teh Wu, Susan Abraham. MD Anderson Cancer Center, Houston; Mayo Clinic, Rochester

Background: Chief cell predominant adenocarcinoma (CCP-AD) is a rare type of gastric carcinoma characterized by phenotypic and immunophenotypic differentiation toward chief cells. These tumors demonstrate low proliferative rates, lack of p53 overexpression, and less aggressive behavior as compared to usual gastric carcinomas. CCP-AD has only recently been described and its morphologic precursor is unknown.
Design: We studied 16 polyps from 10 patients who underwent gastric biopsy (n=7) or resection (n=3). Cases were collected prospectively because of their unusual histology (cytologic dysplasia and architectural atypia of chief cell predominant deep fundic glands). Age, gender, polyp size, morphology, multiplicity, concomitant adenocarcinoma, other gastric polyps, and results of immunohistochemistry for Ki67 and p53 were recorded.
Results: Lesions were centered in the basal aspect of oxyntic mucosa and comprised primarily of chief cells with moderately enlarged nuclei. Involved glands were mildly dilated with budding/anastomosing architecture (n=8), cribriforming (n=1), multilayered cells (n=14), luminal apoptotic debris (n=2), and inspissated basophilic secretions (n=2). In 6 cases, glands were admixed with splayed muscularis mucosae and 2 extended into superficial submucosa. Four lesions also had foveolar dysplasia and one of these abutted a submucosally-invasive CCP-AD. Ki67 immunostaining demonstrated abnormal extension of the proliferative zone down into the deep glandular compartment, although the proliferative rate was low (≤5%). p53 was negative.

Chief Cell Adenomas

Age	Sex	No. polyps	Size	Other lesions
49	M	3	Largest 0.5 cm	FGPs x7
50	F	1	0.3 cm	No
36	M	1	1.7 cm	Chief cell predominant adenocarcinoma
66	M	1	0.2 cm	FGPs x2
77	M	1	0.2 cm	FGP
73	M	1	0.8 cm	FGPs x3
80	M	3	Largest 0.7 cm	No
71	M	5	Largest 0.45 cm	Foveolar adenoma and dysplastic FGP
73	M	1	0.1 cm	No
69	F	1	0.3 cm	No

FGP, fundic gland polyp




Conclusions: We describe a novel gastric polyp and propose the name "chief cell adenoma" based on the presence of cytologic dysplasia of chief cells, architectural atypia, and abnormal Ki67 labeling of deep fundic glands. The occurence of foveolar dysplasia in a subset of these lesions, and one patient with associated CCP-AD, suggest that chief cell adenomas might represent a precursor of CCP-AD.
Category: Gastrointestinal

Monday, March 19, 2012 1:00 PM

Poster Session II # 100, Monday Afternoon