title: Microsatellite instable vs stable colon carcinomas: analysis of tumour heterogeneity, inflammation and angiogenesis.
abstract: BACKGROUND
  Microsatellite instability (MSI) accounts for 15% of all colorectal tumours. Several specific clinicopathologicals (e.g., preference for the proximal colon over the distal colon, improved prognosis and altered response to chemotherapeutics) are described for this subset of tumours. This study aimed to analyse morphological, inflammatory and angiogenic features of MSI vs microsatellite stable (MSS) tumours.
  
  
  METHODS
  Twenty-seven MSS and 29 MSI, TNM stage matched, colorectal tumours were selected from the archive of the Department of Pathology, UZ Leuven. Morphology was analysed on haematoxylin-eosin sections. Immunohistochemistry for CD3, CD4, CD8, CD20 and CD68 was used to map tumour infiltration in both a digital and traditional microscope-based manner for all distinct morphological components of the tumour. CD31 immunostains were performed to assess angiogenesis.
  
  
  RESULTS
  Morphological tumour heterogeneity was a marked feature of MSI tumours, occurring in 53% of the cases as compared with 11% of the MSS tumours (P<0.001). Digital immune quantification showed an increased number of tumour-infiltrating cytotoxic T-lymphocytes (CD8+) in MSI compared with MSS tumours for both the tumour (P=0.02) and peritumoural area (P=0.03). Traditional microscope-based quantification confirmed these results (P<0.001 for both) and, in addition, revealed large numbers of CD68+ macrophages in the peritumoural area of MSI cancers (P=0.001). Moreover, traditional microscope-based analysis was able to distinguish between lymphocytes directly infiltrating the tumoural glands (intra-epithelial) and those infiltrating only the neoplastic stroma around the glands (intratumoural). Quantification showed high numbers of intra-epithelial CD3+, CD4+, CD8+, CD20+ and CD68+ cells in MSI compared with MSS cancers (P<0.001, P=0.01, P<0.001, P<0.001 and P=0.006, respectively). Higher microvessel density (MVD) was observed in MSI tumours compared with their MSS counterpart.
  
  
  CONCLUSIONS
  Mixed morphology, reflecting tumour heterogeneity, is an important feature of MSI tumours and may have both diagnostic and therapeutic impact. The inflammatory reaction also presented with significant differences in MSI vs MSS colorectal tumours. MSI cancers showed mainly infiltration by cytotoxic T-cells in both the tumour and the close border around the tumour, as well as increased intra-epithelial infiltration in contrast to MSS tumours. The type of immune cell and the compartment it resides in (intratumoural or intra-epithelial) depend both on MSI status and morphology. Finally, MSI tumours showed a higher angiogenic capacity represented by an increased MVD, hinting for possible therapeutic consequences.
authors.affiliation: Translational Cell and Tissue Research Unit, Department of Imaging and Pathology, KU Leuven, Minderbroedersstraat 12 blok Q bus 1032, 3000 Leuven, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: De Smedt
authors.affiliation: Department of Pathology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Lemahieu
authors.affiliation: Translational Cell and Tissue Research Unit, Department of Imaging and Pathology, KU Leuven, Minderbroedersstraat 12 blok Q bus 1032, 3000 Leuven, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Palmans
authors.affiliation: Translational Cell and Tissue Research Unit, Department of Imaging and Pathology, KU Leuven, Minderbroedersstraat 12 blok Q bus 1032, 3000 Leuven, Belgium.
authors.forename: O
authors.initials: O
authors.lastname: Govaere
authors.affiliation: 1] Translational Cell and Tissue Research Unit, Department of Imaging and Pathology, KU Leuven, Minderbroedersstraat 12 blok Q bus 1032, 3000 Leuven, Belgium [2] Department of Pathology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: T
authors.initials: T
authors.lastname: Tousseyn
authors.affiliation: Digestive Oncology Unit, Department of Oncology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Van Cutsem
authors.affiliation: Digestive Oncology Unit, Department of Oncology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Prenen
authors.affiliation: Digestive Oncology Unit, Department of Oncology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Tejpar
authors.affiliation: Department of Human Genetics, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Spaepen
authors.affiliation: Department of Human Genetics, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Matthijs
authors.affiliation: 1] DIAPath-Center for Microscopy and Molecular Imaging (CMMI), Rue Adrienne Bolland 8, Gosselies 6041, Belgium [2] Laboratories of Image, Signal Processing and Acoustics, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, Brussels 1050, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Decaestecker
authors.affiliation: 1] DIAPath-Center for Microscopy and Molecular Imaging (CMMI), Rue Adrienne Bolland 8, Gosselies 6041, Belgium [2] Department of Pathology, Erasme Hospital, Université Libre de Bruxelles, Route de Lennik 808, Brussels 1070, Belgium.
authors.forename: X
authors.initials: X
authors.lastname: Moles Lopez
authors.affiliation: Department of Pathology, Erasme Hospital, Université Libre de Bruxelles, Route de Lennik 808, Brussels 1070, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Demetter
authors.affiliation: 1] DIAPath-Center for Microscopy and Molecular Imaging (CMMI), Rue Adrienne Bolland 8, Gosselies 6041, Belgium [2] Department of Pathology, Erasme Hospital, Université Libre de Bruxelles, Route de Lennik 808, Brussels 1070, Belgium.
authors.forename: I
authors.initials: I
authors.lastname: Salmon
authors.affiliation: 1] Translational Cell and Tissue Research Unit, Department of Imaging and Pathology, KU Leuven, Minderbroedersstraat 12 blok Q bus 1032, 3000 Leuven, Belgium [2] Department of Pathology, University Hospitals Leuven, Herestraat 49, Leuven 3000, Belgium.
authors.forename: X
authors.initials: X
authors.lastname: Sagaert
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003110:Colonic Neoplasms / Q000098:blood supply / Q000235:genetics / Q000276:immunology / Q000473:pathology; D005260:Female; D018740:Genetic Heterogeneity; D006801:Humans; D007249:Inflammation / Q000235:genetics* / Q000473:pathology; D008297:Male; D053842:Microsatellite Instability; D018895:Microsatellite Repeats / Q000235:genetics*; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000235:genetics*