Squamous Morules in Gastric Mucosa

An Immunohistochemical Study of Morules in Endometrioid Lesions of the Female Genital Tract: CD10 Is a Characteristic Marker of Morular Metaplasia

“…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).…”

CD10 is a characteristic marker of tumours forming morules with biotin‐rich, optically clear nuclei that occur in different organs

“…They are not related to human papillomavirus infection 6 and are thus different from both squamous metaplasia and carcinoma 1 . Morules with a characteristic nuclear clearing have been reported in endometria, 1,6–10 ovarian endometrioid tumours, 11,12 colorectal adenomas and carcinomas, 13–15 gastric polyps, 16 gallbladder adenomas, 17 pulmonary blastomas, low‐grade adenocarcinomas of fetal lung type, some papillary lung carcinomas, 18–24 pancreatoblastomas 25,26 and, finally, in the cribriform‐morular variant (C‐MV) of papillary thyroid carcinomas 2–5,27–29 . The so‐called ‘peculiar nuclear clearing’ so frequently found in these morules is due to biotin‐rich intranuclear inclusions which ultrastructurally have the appearance of thread‐like fibrils and consequently should not be misinterpreted as intranuclear cytoplasmic pseudoinclusions or as viral inclusion bodies 2,3,15,19,30,31 …”

“…The morules are immunoreactive for cytokeratin (CK) 8 and CK18, the clone AE1/AE3, neuron‐specific enolase, CA19.9 and Bcl‐2, but show no reaction for CK7 or CK20, the clone 34βE12, epithelial membrane antigen or vimentin 4–6,15,33 . Many unrelated antibodies, 6,10,14–21,24,25,33 mainly including hormone receptors, neuroendocrine markers and oncofetal antigens, have been described as positive in the literature; these results remain inconclusive, as they may have been misinterpreted due to false immunopositivity resulting from the use of detection systems with avidin– or streptavidin–biotin binding, cases of squamous metaplasia, and/or organ‐specific differences.…”