Squamous morula formation in colorectal adenoma: Immunohistochemical and molecular analyses.

Little is known about the squamous morular component (SMC) in colorectal neoplasms because of its rarity. The aim of the present study is to elucidate the morphological, immunohistochemical and genetic characteristics of SMCs in colorectal adenomas. Five colorectal adenomas having SMCs were resected from five patients endoscopically. On immunohistochemical examination (four cases), all SMCs were positive for cytokeratin 5/6 in their cytoplasm and positive for β-catenin in their cytoplasm and nuclei. A nuclear positivity of p63 was detected in one SMC. All SMCs were negative for p53, chromogranin A, synaptophysin and NCAM. There was no Ki-67 expression in any of the SMCs. We detected none of mutations of β-catenin, KRAS and BRAF by microdissection and polymerase chain reaction-direct sequence in any of the four examined SMCs. SMCs are a rare but problematic finding in colorectal adenomas. Using immunohistochemistry for β-catenin, cytokeratin 5/6, Ki-67, p53, chromogranin A, synaptophysin and NCAM can facilitate the diagnosis of these peculiar cell nests.