title: Inflammatory cell distribution in primary merkel cell carcinoma.
abstract: Merkel cell carcinoma (MCC) is an aggressive poorly differentiated neuroendocrine cutaneous carcinoma associated with older age, immunodeficiency and Merkel cell polyomavirus (MCPyV) integrated within malignant cells. The presence of intra-tumoural CD8+ lymphocytes reportedly predicts better MCC-specific survival. In this study, the distribution of inflammatory cells and properties of CD8+ T lymphocytes within 20 primary MCC specimens were characterised using immunohistochemistry and multicolour immunofluorescent staining coupled to confocal microscopy. CD8+ cells and CD68+ macrophages were identified in 19/20 primary MCC. CD20+ B cells were present in 5/10, CD4+ cells in 10/10 and FoxP3+ cells in 7/10 specimens. Only two specimens had almost no inflammatory cells. Within specimens, inflammatory cells followed the same patchy distribution, focused at the edge of sheets and nodules and, in some cases, more intense in trabecular areas. CD8+ cells were outside vessels on the edge of tumour. Those few within malignant sheets typically lined up in fine septa not contacting MCC cells expressing MCPyV large T antigen. The homeostatic chemokine CXCL12 was expressed outside malignant nodules whereas its receptor CXCR4 was identified within tumour but not on CD8+ cells. CD8+ cells lacked CXCR3 and granzyme B expression irrespective of location within stroma versus malignant nodules or of the intensity of the intra-tumoural infiltrate. In summary, diverse inflammatory cells were organised around the margin of malignant deposits suggesting response to aberrant signaling, but were unable to penetrate the tumour microenvironment itself to enable an immune response against malignant cells or their polyomavirus.
authors: School of Cancer Sciences and CR UK Centre for Cancer Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK. r.l.wheat@bham.ac.uk.
authors: Rachel
authors: R
authors: Wheat
authors: School of Cancer Sciences and CR UK Centre for Cancer Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK. jerry.marsden@btinternet.com.
authors: Claudia
authors: C
authors: Roberts
authors: Infection and Cancer Program, DKFZ (German Cancer Research Centre), 69120 Heidelberg, Germany. T.Waterboer@Dkfz-Heidelberg.de.
authors: Tim
authors: T
authors: Waterboer
authors: Human Biomaterials Resource Centre, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK. j.c.steele@bham.ac.uk.
authors: Jane
authors: J
authors: Steele
authors: University Hospitals Birmingham NHS Foundation Trust, New Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, Birmingham, B15 2WB, UK. jerry.marsden@btinternet.com.
authors: Jerry
authors: J
authors: Marsden
authors: School of Cancer Sciences and CR UK Centre for Cancer Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK. jerry.marsden@btinternet.com.
authors: Neil M
authors: NM
authors: Steven
authors: Department of Microbial and Cellular Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK. d.blackbourn@surrey.ac.uk.
authors: David J
authors: DJ
authors: Blackbourn