title: Gastric medullary carcinoma, a distinct entity associated with microsatellite instability-H, prominent intraepithelial lymphocytes and improved prognosis.
abstract: OBJECTIVE
  To determine the clinicopathological and molecular features of gastric medullary cancer.
  
  
  RESULTS
  Clinicopathological review and microsatellite instability (MSI) analysis were carried out on 17 gastric medullary and 64 non-medullary cancers. In addition to characteristic histopathology, gastric medullary cancers had certain prominent features: (i) the average survival time was longer in medullary and low-grade non-medullary cancers than in high-grade (P = 0.004); (ii) serosal involvement was less common in medullary cancers (29.4%, 5/17) than in non-medullary cancers (9.4%, 6/64) (P < 0.05) while pushing borders were more common in medullary cancers (70.6%, 12/17 versus 17.2%, 11/64, P = 0); (iii) the presence of intraepithelial lymphocytes (IELs) in medullary and non-medullary cancers was 2380/10 high-power field (HPF) and 147/10 HPF (P = 0), respectively. Both peritumoural infiltrating lymphocytes (pTIL) and a Crohn's-like reaction were more common in medullary cancers than in non-medullary (pTIL 35.3%, 6/17 versus 3.1%, 2/64; a Crohn's-like reaction 70.6%, 12/17 versus 32.8%, 21/64; P < 0.05); (iv) medullary and high-grade non-medullary cancers were more associated with reduced ECD expression in comparison with low-grade cancers (P < 0.05); (v) higher MSI-H (Bat26+) rate was observed in medullary cancers (41.2%, 7/17) than in non-medullary (1.6%, 1/64) (P = 0).
  
  
  CONCLUSIONS
  Gastric medullary cancer has distinct clinicopathological features and genetic alterations. Two subtypes of gastric medullary cancers, Bat26+ and Bat26-, might have prognostic implications, thus analysis of Bat26 may be of clinical value.
authors.affiliation: Department of Anatomical & Cellular Pathology, the affiliated Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China.
authors.forename: B-J
authors.initials: BJ
authors.lastname: Lü
authors.forename: M
authors.initials: M
authors.lastname: Lai
authors.forename: L
authors.initials: L
authors.lastname: Cheng
authors.forename: J-Y
authors.initials: JY
authors.lastname: Xu
authors.forename: Q
authors.initials: Q
authors.lastname: Huang
mesh_terms: D018276:Carcinoma, Medullary / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D005260:Female; D042822:Genomic Instability; D006801:Humans; D008214:Lymphocytes / Q000473:pathology; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D011379:Prognosis; D013274:Stomach Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*