title: Collision tumor of the rectum: a case report of metastatic gastric adenocarcinoma plus primary rectal adenocarcinoma.
abstract: Collision tumors are thought to arise from the accidental meeting and interpenetration of two independent tumors. We report here a highly unusual case of a 61-year old man who had a unique tumor that was composed of a metastatic adenocarcinoma from the stomach to the rectum, which harbored a collision tumor of primary rectal adenocarcinoma. The clonalities of the two histologically distinct lesions of the rectal mass were confirmed by immunohistochemical and molecular analysis. Although histologic examination is the cornerstone in pathology, immunohistochemical and molecular analysis can provide evidence regarding whether tumors originate from the same clone or different clones. To the best of our knowledge, this is the first reported case of such an occurrence.
authors.affiliation: Department of Pathology, Dong-A University College of Medicine 1, 3-ga, Dongdaeshin-dong, Seo-gu, Busan 602-715, Korea. msroh@dau.ac.kr.
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Roh
authors.forename: Hyoun-Wook
authors.initials: HW
authors.lastname: Lee
authors.forename: Min-Chan
authors.initials: MC
authors.lastname: Kim
authors.forename: Kyeong-Woo
authors.initials: KW
authors.lastname: Lee
authors.forename: Mee-Sook
authors.initials: MS
authors.lastname: Roh
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology* / Q000556:secondary*; D042822:Genomic Instability; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary; D012004:Rectal Neoplasms / Q000235:genetics / Q000473:pathology* / Q000556:secondary*; D013274:Stomach Neoplasms / Q000235:genetics / Q000473:pathology*