Fine-needle aspiration (FNA) of the thyroid gland:Analysis of discrepancies between cytological and histological diagnoses,Feinnadelaspiration (FNA) der Schilddrüse: Analyse diskrepanter zytologischer und histologischer Diagnosen

BACKGROUND: Diagnostic problems of thyroid cytology are frequently discussed, but relevance and causes of discrepant cytological and histological diagnoses are rarely studied in detail.

OBJECTIVES: Investigation of causes and relevance of discrepant diagnoses.

MATERIALS AND METHOD: The analysis includes 297 patients who had thyroid resection after prior fine needle aspiration (FNA) and is based on the cytological and histological reports. In special cases, cytological and histological specimens were re-examined.

RESULTS: Malignant tumors were found in 45 patients (15.1 %). In 5 patients the cytological diagnosis was "false negative". Three of these 5 tumors were papillary carcinomas (PTC) of ≤10 mm, one an obviously nonmalignant papillary proliferation of the thyroidal epithelium and one a malignant lymphoma complicating autoimmune thyreoiditis (AIT). In 11 of the 35 patients with a FNA diagnosis "suspicious of malignancy" or "malignant," 1 AIT, 4 goiter nodules, and 6 adenomas were diagnosed histologically. However, since distinct nuclear atypia was found in three of five false positive diagnoses, there still remains doubt in their benignity.

CONCLUSIONS: Carcinomas of ≤10 mm incidentally detected in the resected thyroid tissue may not be relevant to the patient and do not reduce the high negative predictive value of FNA. The final diagnosis on the resected tissue should include the cytological findings. Discrepant findings should be commented in the report to the clinician.