title: Neuroendocrine (Merkel cell) carcinoma of the retroperitoneum with no identifiable primary site.
abstract: BACKGROUND
  Neuroendocrine carcinoma is an aggressive neoplasm that mainly affects elderly Caucasians and typically arises in sun-exposed areas of the skin. The disease is rather rare and only a relatively few cases present with no apparent primary lesion.
  
  
  METHODS
  We report a case of an 81-year-old Caucasian male with neuroendocrine carcinoma, which initially presented as a large retroperitoneal mass. Pathological and immunohistochemical analysis of the transabdominal CT-guided biopsy specimen revealed tissue consistent with neuroendocrine carcinoma. The patient underwent exploratory laparotomy and the mass was successfully excised along with an associated mesenteric lymph node.
  
  
  CONCLUSIONS
  There are currently two possible explanations for what occurred in our patient. First, the retroperitoneal mass could be a massively enlarged lymph node where precursor cells became neoplastic. This would be consistent with a presumptive diagnosis of primary nodal disease. Alternatively, an initial skin lesion could have spontaneously regressed and the retroperitoneal mass represents a single site of metastasis. Since Merkel cell precursors have never been identified within lymph nodes, the latter theory seems more befitting. Moreover, metastasis to the retroperitoneal lymph nodes has been reported as relatively common when compared to other sites such as liver, bone, brain and skin.
  
  
  CONCLUSIONS
  Wide local excision of the primary tumor is the surgical treatment of choice for localized disease. We propose that further studies are needed to elucidate the true efficacy of chemotherapy in conventional as well as unconventional patients with neuroendocrine carcinoma.
authors.affiliation: Department of Surgery, Brooklyn Hospital Center, 121 Dekalb Ave, Brooklyn, New York, NY 11201, USA. vanboghossian@aol.com
authors.forename: Van
authors.initials: V
authors.lastname: Boghossian
authors.forename: Ira D
authors.initials: ID
authors.lastname: Owen
authors.forename: Balakrishna
authors.initials: B
authors.lastname: Nuli
authors.forename: Philip Q
authors.initials: PQ
authors.lastname: Xiao
mesh_terms: D000369:Aged, 80 and over; D001707:Biopsy, Needle; D015266:Carcinoma, Merkel Cell / Q000556:secondary* / Q000601:surgery; D018278:Carcinoma, Neuroendocrine / Q000556:secondary* / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D007150:Immunohistochemistry; D007813:Laparotomy / Q000379:methods; D008198:Lymph Nodes / Q000473:pathology* / Q000601:surgery; D008297:Male; D009367:Neoplasm Staging; D009382:Neoplasms, Unknown Primary / Q000473:pathology*; D012186:Retroperitoneal Neoplasms / Q000556:secondary* / Q000601:surgery; D018570:Risk Assessment; D016896:Treatment Outcome