title: Isolated carcinoid tumor metastatic to the thyroid gland: report of a case initially diagnosed by fine needle aspiration cytology.
abstract: BACKGROUND
  Neuroendocrine tumor metastatic to the thyroid gland is rare and may be difficult to differentiate from primary thyroid neuroendocrine tumors, such as medullary thyroid carcinoma (M/ITC). This report describes an unusual case of bronchial carcinoid metastatic to the thyroid diagnosed by fine needle aspiration cytology (FNAC).
  
  
  METHODS
  A 42-year-old woman with an undiagnosed bronchial carcinoid tumor presented to our clinic with a solitary nodule in the thyroid gland. FNAC of the nodule showed loosely cohesive groups of cuboidal tumor cells with scant, slightly granular cytoplasm; centrally located nuclei with a coarsely granular, salt-and-pepper chromatin pattern and inconspicuous nucleoli. Immunocytochemically the tumor cells were positive for neuron-specific enolase, chromogranin and synaptophysin and negative for thyroglobulin, calcitonin and carcinoembryonic antigen. The cytologic diagnosis of a metastatic neuroendocrine carcinoma was confirmed histologically.
  
  
  CONCLUSIONS
  Metastasis to the thyroid gland may pose a diagnostic problem, particularly with tumors of neuroendocrine origin, as these have similar cytologic features in various organs. The correct preoperative cytologic diagnosis of metastatic carcinoid tumor in patients without a prior history of cancer and differential diagnosis with MTC are crucial because prognosis, workup and treatment are different in each.
authors.affiliation: Department of Pathology, Hadassah University Hospital, Jerusalem, Israel. maly_bella@yahoo.com
authors.forename: Alexander
authors.initials: A
authors.lastname: Maly
authors.forename: Karen
authors.initials: K
authors.lastname: Meir
authors.forename: Bella
authors.initials: B
authors.lastname: Maly
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000378:metabolism; D044963:Biopsy, Fine-Needle; D001984:Bronchial Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D002276:Carcinoid Tumor / Q000175:diagnosis* / Q000378:metabolism / Q000556:secondary; D002466:Cell Nucleolus / Q000378:metabolism / Q000473:pathology; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D002843:Chromatin / Q000378:metabolism; D005260:Female; D006801:Humans; D013961:Thyroid Gland / Q000378:metabolism / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology / Q000556:secondary
chemical_list: D014408:Biomarkers, Tumor; D002843:Chromatin