Diagnostic importance of CD56 with fine-needle aspiration cytology in suspected papillary thyroid carcinoma cases

BACKGROUND: Palpable thyroid nodules can be found in 4%–7% of the adult population; however, <5% of thyroid nodules are malignant. Immunohistochemical markers, such as CD56, can be used to make a differential diagnosis between benign and malignant lesions. To increase the accuracy of the diagnosis and distinguish the malignant aspirates from the benign ones, chose to evaluate CD56, which is normally found in benign thyroid tissue. METHODS: A total of 53 fine-needle aspirate samples from patients diagnosed with suspected papillary thyroid carcinoma (PTC) were included prospectively. These aspirates were immunocytochemically stained for CD56. RESULTS: In histopathological examination, the fine-needle aspiration cytopathology specimens suspicious for PTC (after undergoing surgery) showed that 32 (60.4%) were benign and 21 (39.6%) were malignant. Thirty-one of the benign cases (96.87%) were CD56-positive, whereas the last case (3.13%) was CD56-negative. Staining was not seen in any of the malignant cases. CONCLUSIONS: We believe that CD56 is an important marker in the definitive diagnosis of suspected PTC cases, with CD56-positivity being interpreted in favor of benignity.