['Altered cyclin D1 (CD1), a cell cycle regulator, may play an important role in imparting aggressive nature to esophageal adenocarcinoma (EAC). CD1 gene single nucleotide polymorphism G/A870 results in two alternatively spliced transcripts, CD1a and CD1b. CD1b, preferentially encoded by the A870 allele, is putatively oncogenic. We hypothesized that CD1 A870 allele would be associated with higher CD1 protein expression, and increased genomic instability during EAC evolution, leading to more aggressive phenotype.', "One hundred twenty-four archival specimens of EAC, and 39 associated Barrett's esophagus (BE) specimens were examined for CD1 genotype, CD1 protein expression, and chromosome 9 polysomy (representing genomic instability). We correlated CD1 genotypes with CD1 protein expression, genomic instability, age at diagnosis of EAC, and overall survival (OS).", 'The A870 allele was associated with higher levels of CD1 protein expression in EAC (P = .032); in BE (P = .01) where it was associated with concomitant increased chromosome 9 polysomy (P = .002); and with a younger age at diagnosis (P < .001) and poor OS (P = .0003) of EAC patients.'] Is cyclin D1 guanine/adenine 870 polymorphism with altered protein expression associated with genomic instability and aggressive clinical biology of esophageal adenocarcinoma?