Purpose:To analyze immunohistochemically morules in endometrioid lesions to show that CD10 is a sensitive marker for morular metaplasia. Experimental Design: Immunohistochemical analysis of 53 instances of morular metaplasia comprising 1 cyclic endometrium and 52 endometrioid lesions associated with focal glandular complexity corresponding to 9 polyps, 4 atypical polypoid adenomyomas, 24 complex endometrial hyperplasias (18 with and 6 without atypia), 12 grade 1 endometrioid adenocarcinomas in early clinical stages of both uterus and ovary, and three ovarian adenofibromas. Immunohistochemistry in paraffin sections was done for CD10, h-catenin, estrogen and progesterone receptors, and cytokeratins 5-6, 7, 8, 13, 18, 19, 20, and 34h-E12. Results: Morules were negative for estrogen and progesterone receptors and had h-cateninp ositive nuclei. Cytokeratins 8, 18, 19 were positive; cytokeratins 7 and 20 were negative; and cytokeratins 5-6, 13, and 34h-E12 were weakly positive. All cases revealed strongly positive membranous CD10 staining in morules, which was absent in glands. CD10 positivity allowed easy identification of morules at low power in various types of surgical specimens and in curettings. CD10 also highlighted early morular metaplasia in glandular epithelium. In cases associated with squamous, keratinizing metaplasia, CD10 discriminated between both types of metaplasia. Conclusions: CD10 staining represents a useful marker of morules in endometrioid neoplasms of the female genital tract, permitting identification of lesions usually associated with an attenuated malignancy. Considering the immunohistochemical and genetic similarities of morules in tumors of different organs, it is likely that this marker may be also useful to diagnose morular metaplasia in similar neoplasms of extragenital locations.Morules (1) are nodular structures found in endometrial-type glands formed by a peculiar metaplastic non-keratinizing squamoid epithelium (2). Morphologically similar structures have also been described in neoplastic lesions in other anatomic sites, such as thyroid (3), lung (4, 5), stomach (6), pancreas (7), and colon (8).In both eutopic and ectopic endometrioid tissues, morules are almost invariably associated with the glandular architectural complexity of premalignant and low-grade glandular malignant lesions but are absent in high-grade ones. Thus, it can be said that the presence of morules in the endometrium relates well with an attenuated malignancy.This study deals with the immunohistochemical findings in a series of 53 cases of morular metaplasia from both uterus and ovary, showing for the first time that CD10 staining is a marker of morules, allowing its easy identification in various endometrioid lesions.
Materials and MethodsA total of 53 cases of endometrioid morular metaplasia were collected from the files of the
