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Detection of the CD56+/CD45− immunophenotype by flow cytometry in neuroendocrine malignancies
  1. G J Bryson1,
  2. D Lear3,
  3. R Williamson2,
  4. R C W Wong1
  1. 1Division of Immunology, Queensland Health Pathology Services, Royal Brisbane Hospital, Herston, Queensland 4029, Australia
  2. 2Division of Anatomical Pathology, Queensland Health Pathology Services
  3. 3Sullivan Nicolaides Pathology, Taringa, Queensland 4068, Australia
  1. Correspondence to:
 Dr R C W Wong, Division of Immunology, Queensland Health Pathology Services, Royal Brisbane Hospital, Herston 4029, Queensland, Australia;


Aims: Antibodies against CD56 are primarily used in flow cytometric studies to detect natural killer cells. However, they may be useful in the identification of neuroendocrine malignancies, especially if the cells do not express CD45, indicating a non-leucocyte origin.

Methods: A retrospective review was conducted on all solid tissue flow cytometric studies performed between January 1997 and September 2001, to identify all cases with a CD56+/CD45− immunophenotype.

Results: Twelve neuroendocrine malignancies (five metastatic small cell carcinomas, three Merkel cell carcinomas, two metastatic undifferentiated neuroendocrine carcinomas, one metastatic pancreatic neuroendocrine carcinoma, and one neuroblastoma) were identified.

Conclusions: CD56+/CD45− neuroendocrine malignancies are only rarely detected in the flow cytometric analysis of solid tissue samples. However, the recognition of this immunophenotype is important to avoid their misclassification as natural killer cell malignancies. Furthermore, flow cytometry assists in the rapid identification of such cases, so that appropriate immunohistochemical studies can be performed to facilitate their correct diagnosis.

  • CD56
  • CD45
  • neuroendocrine
  • flow cytometry
  • CD, cluster differentiation
  • FITC, fluorescein isothiocyanate
  • NK, natural killer
  • PE, phycoerythrin
  • PECY5, phycoerythrin-cyanin 5 tandem

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