Poorly cohesive cell (diffuse-infiltrative/signet ring cell) carcinomas of the gallbladder: clinicopathological analysis of 24 cases identified in 628 gallbladder carcinomas

Signet ring cell carcinoma is an extremely rare type of gallbladder carcinoma: In the gastrointestinal system, carcinomas with single-cell or cord-like infiltration, previously called "diffuse-infiltrative" type or "signet ring cell," are now designated as "poorly cohesive cell" (PCC) type (regardless of with/without signet ring cells) in the World Health Organization 2010 classification. Six hundred twenty-eight primary invasive gallbladder carcinomas were reviewed for the PCC pattern. Twenty-four cases in which classical PCC pattern constituted greater than 50% of the tumor were included in the study. The mean age was 63 (range, 44-84) years. A strong female predominance was present (female/male ratio, 6.3 versus 3.9 for all gallbladder carcinomas). Most cases (79%) had advanced carcinoma (pT3+) in comparison with 51% of usual carcinomas (P < .01). All cases (100%) showed at least focal signet ring morphology (intracytoplasmic mucin), and this was predominant in 50%. Twelve cases (50%) demonstrated a focal invasive glandular component of the usual type. Overlying focal high-grade dysplasia was identified in 11 (46%). Due to block loss, immunohistochemistry could be performed in only 5 cases and revealed a profile similar to upper gastrointestinal carcinomas CK7++/CK20-+/CDX2+-/p53+. E-cadherin was decreased in the PCC component of all cases. The clinical course appeared to be more aggressive than ordinary gallbladder. carcinomas, with median survival of 3.3 months versus 11.8 months, which did not reach statistical significance (P = .06 by log-rank test). In conclusion, PCC carcinoma originating in the gallbladder should be kept in mind for the differential diagnosis of disseminated poorly differentiated carcinomas in the abdomen. (C) 2016 Elsevier Inc. All rights reserved.