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Misplaced glands in colonic polyps are important to identify and to differentiate from invasive adenocarcinomas. Certain microscopic features are considered helpful to make this distinction. We have examined 650 polyps and found 23 (3%) with misplaced glands. A significant number (17 of 23 cases) lacked the typical previously described microscopic features of misplaced glands. Two distinct growth patterns of the misplaced glands were identified in our series: an infiltrative and a pushing pattern, both lacking stromal desmoplasia. Only six of the 23 polyps showed the previously described associated changes such as hemorrhage and mucin pools. In addition, five of the polyps had high-grade dysplasia in the misplaced glands, four of which showed the infiltrative pattern of growth. Two cases were associated with a synchronous adenocarcinoma of the colon. The recognition of these two patterns of misplaced glands with or without stromal changes, and the association with high-grade dysplasia should be considered in the differential diagnosis between misplaced glands and adenocarcinoma. Int J Surg Pathol 7(2):73-77, 1999
Key words: colon polyps, misplaced glands, pushing and infiltrative microscopic patterns.
Misplaced glands, also referred to as pseudoinvasive glands, is a feature found in some colonic polyps and its significance is due to its microscopic resemblance to invasive carcinoma. Misplaced glands are defined as the misplacement or displacement of glandular epithelium including lamina propria into the submucosa, not continuous with the surface epithelium of the polyp [1,2]. The incidence of misplaced glands has been reported to range from 2 % to 11% in the largest studies [3-5]. Consistent microscopic findings described in cases of misplaced glands include cystic changes of glands with and without mucin pools, absence of desmoplasia, and the presence of stromal hemosiderin or recent hemorrhage. The presence of high-grade dysplasia in misplaced glands presents an even more difficult diagnostic dilemma and has been dealt with in only one individual case study [6]. Over the last few years we have encountered a number of colonic polyps with misplaced glands that do not have any of the previously described microscopic features. Therefore, we decided to review the incidence of misplaced glands in polyps of the entire colon, including their location and size, and microscopic features of the misplaced glands, including their growth pattern and the association...