title: Merkel cell carcinoma of unknown primary origin.
abstract: BACKGROUND
  Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin. MCC from an unknown primary origin (MCCUP) can present a diagnostic and therapeutic challenge. We describe our single-institution experience with the diagnosis and management of MCCUP presenting as metastases to lymph nodes.
  
  
  METHODS
  After institutional review board approval, our institutional database spanning the years 1998-2010 was queried for patients with MCCUP. Clinicopathologic variables and outcomes were assessed.
  
  
  RESULTS
  From a database of 321 patients with MCC, 38 (12%) were identified as having nodal MCCUP. Median age was 67 years, and 79% were men. Nodal basins involved at presentation were cervical (58%), axillary/epitrochlear (21%), or inguinal/iliac (21%). CK20 staining was positive in 93% of tumors tested, and all were negative for thyroid transcription factor-1. Twenty-nine patients (76%) underwent complete regional lymph node dissection (LND): 3 had LND alone, ten had LND and adjuvant radiotherapy, and 16 underwent LND followed by chemoradiotherapy. Definitive chemoradiotherapy without surgery was provided to six patients (16%), while radiotherapy alone was provided to three (8%). Recurrence was observed in 34% of patients. Median recurrence-free survival was 35 months. Ten patients (26%) died, five of disease and five of other causes. The median overall survival was 104 months.
  
  
  CONCLUSIONS
  Nodal MCCUP is a rare disease affecting primarily elderly white men. Recurrence is observed in approximately one-third of patients, with a 104 month median overall survival after a multimodal treatment approach consisting of surgery along with adjuvant chemotherapy and radiotherapy in the majority of patients.
authors.affiliation: Department of Cutaneous Oncology, Moffitt Cancer Center, Tampa, FL, USA.
authors.forename: Jeremiah L
authors.initials: JL
authors.lastname: Deneve
authors.forename: Jane L
authors.initials: JL
authors.lastname: Messina
authors.forename: Suroosh S
authors.initials: SS
authors.lastname: Marzban
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Gonzalez
authors.forename: Brooke M
authors.initials: BM
authors.lastname: Walls
authors.forename: Kate J
authors.initials: KJ
authors.lastname: Fisher
authors.forename: Y Ann
authors.initials: YA
authors.lastname: Chen
authors.forename: C Wayne
authors.initials: CW
authors.lastname: Cruse
authors.forename: Vernon K
authors.initials: VK
authors.lastname: Sondak
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Zager
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015266:Carcinoma, Merkel Cell / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D009367:Neoplasm Staging; D009382:Neoplasms, Unknown Primary / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate