Merkel Cell Carcinoma Patients Presenting Without a Primary Lesion Have Elevated Markers of Immunity, Higher Tumor Mutation Burden, and Improved Survival

Clin Cancer Res. 2018 Feb 15;24(4):963-971. doi: 10.1158/1078-0432.CCR-17-1678. Epub 2017 Dec 15.


Purpose: Patients presenting with nodal Merkel cell carcinoma without an identifiable (unknown) primary lesion (MCC-UP) are nearly twice as likely to survive compared with similarly staged patients with known primary lesions (MCC-KP). The basis of this previously reported finding is unclear.Experimental Design: Survival analyses and markers of immunity were evaluated in 123 patients with advanced MCC. Whole-exome sequence data were analyzed from 16 tumors.Results: As in prior studies, patients with nodal MCC-UP had strikingly improved MCC-specific survival as compared with MCC-KP patients (HR, 0.297; P < 0.001). Surprisingly, patients presenting with distant metastatic MCC-UP also had significantly improved survival (HR, 0.296; P = 0.038). None of the 72 patients with MCC-UP were immunosuppressed as compared to 12 of the 51 (24%) patients with MCC-KP (P < 0.001). Merkel polyomavirus oncoprotein antibody median titer was higher in MCC-UP patients (26,229) than MCC-KP patients (3,492; P < 0.001). In addition, the median number of nonsynonymous exome mutations in MCC-UP tumors (688 mutations) was markedly higher than MCC-KP tumors (10 mutations, P = 0.016).Conclusions: This is the first study to our knowledge to explore potential underlying immune-mediated mechanisms of MCC-UP presentation. In this cohort, MCC-UP patients were never immune suppressed, had higher oncoprotein antibody titers, and higher tumor mutational burdens. In addition, we show that nodal tumors identified in MCC-UP patients did indeed arise from primary skin lesions as they contained abundant UV-signature mutations. These findings suggest that stronger underlying immunity against MCC contributes to primary lesion elimination and improved survival. Clin Cancer Res; 24(4); 963-71. ©2017 AACR.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Biomarkers, Tumor / genetics
  • Biomarkers, Tumor / immunology*
  • Biomarkers, Tumor / metabolism
  • Carcinoma, Merkel Cell / genetics
  • Carcinoma, Merkel Cell / immunology*
  • Carcinoma, Merkel Cell / therapy
  • Exome Sequencing
  • Female
  • Humans
  • Immunotherapy / methods
  • Lymphatic Metastasis
  • Male
  • Middle Aged
  • Mutation*
  • Skin / immunology*
  • Skin / metabolism
  • Skin / pathology
  • Skin Neoplasms / genetics
  • Skin Neoplasms / immunology*
  • Skin Neoplasms / therapy
  • Survival Analysis
  • Tumor Burden / genetics
  • Tumor Burden / immunology*


  • Biomarkers, Tumor