title: CD56 expression of neuroendocrine neoplasms on immunophenotyping by flow cytometry: a novel diagnostic approach to fine-needle aspiration biopsy.
abstract: BACKGROUND
  CD56 antigen or NCAM (neural cell adhesion molecule) has an established role in the diagnosis of non-Hodgkin lymphoma (NHL)-natural killer cell type and other hematologic malignancies. Therefore, it is included routinely in the panel of antibodies for flow cytometric (FC) analysis of suspected lymphomatous tissue specimens obtained from fine-needle aspiration biopsy (FNAB). The authors evaluated the role of CD56 expression on FC of neuroendocrine (NE) tumors. An initial diagnosis of NHL was suspected based on an on-site FNAB evaluation.
  
  
  METHODS
  Ten FNABs were identified from the cytopathology files at The Johns Hopkins Hospital, Baltimore, MD (2000-2001). Flow cytometric analysis was negative for NHL but revealed a CD56-positive nonlymphoid cell population. An FNAB evaluation was performed on air-dried Diff-Quik-stained smears and FC analysis used a fixed panel of 12 antibodies (B-cell markers, T-cell markers, CD33, CD56, and CD71). Immunoperoxidase staining (IPOX) was performed on the cell block sections from four of the tissue specimens using epithelial and NE markers, CD56, desmin, and O13 antibodies. Sites of FNAB included the lung (five cases), liver (one case), lymph node (three cases), and peritoneum (one case). Only one patient had a history of cancer at the time of FNAB.
  
  
  RESULTS
  All cytologic diagnoses were confirmed by histopathologic follow-up on resection or biopsy or both. Diagnoses included small cell carcinoma (eight cases), Merkel cell carcinoma (one case), and primitive neuroectodermal tumor/Ewing sarcoma (one case). All tissue specimens that underwent IPOX stained strongly with NE markers, with one tissue section staining only with O13.
  
  
  CONCLUSIONS
  CD56 expression by FC in the presence of negative immunostaining with lymphoid markers represented a unique yet highly specific method for the diagnosis of NE tumors by FNAB. This procedure eliminated the need for further IPOX studies on the already limited cytologic sample and provided a timely and accurate diagnosis.
authors.affiliation: Department of Pathology, The Johns Hopkins Hospital, Baltimore, Maryland, USA.
authors.forename: Maryam A
authors.initials: MA
authors.lastname: Farinola
authors.forename: Edward G
authors.initials: EG
authors.lastname: Weir
authors.forename: Syed Z
authors.initials: SZ
authors.lastname: Ali
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D001707:Biopsy, Needle; D019002:CD56 Antigen / Q000032:analysis* / Q000096:biosynthesis*; D003937:Diagnosis, Differential; D005260:Female; D005434:Flow Cytometry; D005819:Genetic Markers; D006801:Humans; D016130:Immunophenotyping; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000235:genetics*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D019002:CD56 Antigen; D005819:Genetic Markers