Beta-Catenin Nuclear Expression in Squamoid Morules in Colorectal Adenomas: Clinicopathologic Study of Fifteen Cases

Abstract

Abstract Introduction/Objective Squamoid morules are an intriguing finding rarely seen in colorectal adenomas, mimicking foci of microinvasion or neuroendocrine differentiation. Previous observations include mostly case reports and small series, with few examining the squamoid morules in detail. Methods/Case Report We identified fifteen colorectal adenomas with squamoid morules and collected clinicopathological data including age, sex, procedure, location, pathologic diagnosis, and size. A representative block was chosen for immunohistochemistry in each case. The expression of p40, p63, CK5/6, beta-catenin, synaptophysin, chromogranin, and Ki-67 in squamoid morules were examined immunohistochemically. Results (if a Case Study enter NA) The fifteen patients comprised thirteen males and two females ranging in age from 45 to 85 years (average: 60.6 years old). The adenomas were removed by endoscopic resection (n = 7) or surgical resection (n = 8). Nine adenomas were found in the rectosigmoid colon, one in the descending colon, and five in the right colon. Eleven adenomas were tubulovillous adenomas (average: 3.8 cm, ranging 1.0 to 6.0 cm) and four were tubular adenomas (average: 2.6 cm, ranging 1.6 to 3.0 cm). Seven adenomas contained invasive adenocarcinoma. Squamoid morules were randomly distributed in adenomas. All foci of squamoid morules showed beta-catenin nuclear positivity and most (more than 90 %) showed CK5/6 expression. Squamoid morules were focally positive for p63 in three adenomas and focally positive for p40 in one adenoma. In one adenoma squamoid morules are positive for both synaptophysin and chromogranin. In all fifteen adenomas squamoid morules were negative for Ki- 67. Conclusion Squamoid morules are characterized by strong male predominance, association with large adenoma size, beta-catenin nuclear positivity, CK5/6 expression, and no Ki-67 expression. Beta-catenin nuclear expression is helpful in distinguishing squamoid morules from foci of microinvasion.