2026-10-23T22:58:01Zhttps://gumushane-rdlopen.rawdatalibrary.net/oai/request

oai:gumushane-rdlopen.rawdatalibrary.net:gumushane/161382026-10-23T18:25:57Zopenairedrivercom_gumushane_10000col_gumushane_10001

DIAGNOSTIC CHALLENGE OF PRIMARY COLONIC POORLY COHESIVE ADENOCARCINOMA EXHIBITING GASTRIC-TYPE IMMUNOHISTOCHEMISTRY PROFILE AND FOCAL SIGNET-RING DIFFERENTIATIONISSiN, GizemTok, MerveÇAgATAY, Diren VuslatGökçe, Oruc NumanAytekin, Faruk Onderprimary colonic poorly cohesive adenocarcinomagastric-type immunophenotypesignet-ring cell differentiationMLH1/PMS2 deficiencyPD-L1 expressionColorectal adenocarcinoma infrequently exhibits a diffuse, poorly cohesive architecture and a gastric-type immunophenotype, closely resembling diffuse-type gastric carcinoma and posing a formidable diagnostic challenge. This report describes a 65-year-old woman who presented with non-specific abdominal discomfort and was found by colonoscopy to have a 6.5 cm ulceroinfiltrative lesion in the hepatic flexure. Histologically, the tumor comprised discohesive cells with focal signet-ring morphology, accompanied by extensive lymphovascular and perineural invasion, necrosis, and a marked peritumoral lymphoid response. Immunohistochemical analysis demonstrated a gastric-type profile (CK7+, CK20-, SATB2-, CDX2 weak/focal, MUC5AC+, MUC2-), whereas panels excluding breast, urothelial, M & uuml;llerian, neuroendocrine, and hematolymphoid differentiation were uniformly negative. Comprehensive imaging and endoscopic evaluation excluded an extra-colonic primary malignancy/ carcinoma. Mismatch repair testing revealed loss of MLH1/PMS2 expression with preserved MSH2/MSH6. This case underscores that, in such uncommon colorectal variants, reliance on immunophenotype alone may mislead, and that definitive diagnosis necessitates integrated clinicopathologic correlation, exhaustive sampling, and exclusion of alternative primaries/primary malignancies/carcinomas to confirm a primary colonic poorly cohesive adenocarcinoma with focal signet-ring differentiation.VESALIUS UNIV MEDICAL PUBL2025Articlehttps://rdlopen.rawdatalibrary.net/r/gumushane/16138https://doi.org/10.5114/pjp.2025.1592801233-9687enPOLISH JOURNAL OF PATHOLOGYinfo:eu-repo/semantics/openAccessinfo:eu-repo/semantics/articlehttps://gumushane-rdlopen.rawdatalibrary.net/tr/items/gumushane/16138