title: A better prognosis for Merkel cell carcinoma of unknown primary origin.
abstract: BACKGROUND
  There is limited evidence that Merkel cell carcinoma (MCC) arising from a nodal basin without evidence of a primary cutaneous (PC) site has better prognosis. We present our experience at 2 tertiary care referral centers with stage III MCC with and without a PC site.
  
  
  METHODS
  Fifty stage III MCC patients were identified between 1996 and 2011. Clinical data were analyzed, with primary endpoints being disease-free survival and overall survival.
  
  
  RESULTS
  Of stage III patients, 34 patients presented with a PC site and 16 patients with an unknown primary (UP) site. Treatment strategies varied; of patients with UP vs. PC sites, 25% vs. 44% underwent combined regional lymphadenectomy and radiation, with an additional 25% vs. 15% receiving chemotherapy. The median disease-free survival for a UP site was not reached vs. 15 months for a PC site (hazards ratio = .48, P = .18). The median overall survival for a UP site was not reached vs 21 months for a PC site (hazards ratio = .34, P = .03). Multivariate analysis showed that UP status was a significant factor in overall survival (P = .002).
  
  
  CONCLUSIONS
  Stage III MCC with a UP site portends a better prognosis than MCC with a PC site.
authors.affiliation: Department of Surgical Oncology, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA. Electronic address: Kathryn.chen@fccc.edu.
authors.forename: Kathryn T
authors.initials: KT
authors.lastname: Chen
authors.forename: Pavlos
authors.initials: P
authors.lastname: Papavasiliou
authors.forename: Kyle
authors.initials: K
authors.lastname: Edwards
authors.forename: Fang
authors.initials: F
authors.lastname: Zhu
authors.forename: Clifford
authors.initials: C
authors.lastname: Perlis
authors.forename: Hong
authors.initials: H
authors.lastname: Wu
authors.forename: Aruna
authors.initials: A
authors.lastname: Turaka
authors.forename: Adam
authors.initials: A
authors.lastname: Berger
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Farma
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015266:Carcinoma, Merkel Cell / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009382:Neoplasms, Unknown Primary / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D011379:Prognosis; D012878:Skin Neoplasms / Q000401:mortality* / Q000473:pathology / Q000628:therapy
keywords: Merkel cell carcinoma; Nodal metastasis; Survival; Unknown primary