Histopathologic Findings Related to the Indeterminate or Inadequate Results of Fine-Needle Aspiration Biopsy and Correlation with Ultrasonographic Findings in Papillary Thyroid Carcinomas

Objective: To determine histopathologic findings related to the indeterminate or inadequate result of fine-needle aspiration biopsy (FNAB) in papillary thyroid carcinomas (PTCs) and to correlate histopathological findings with ultrasonographic features of tumors. Materials and Methods: We retrospectively reviewed the medical records of FNAB, histopathologic characteristics, and sonographic findings of the solid portion of 95 PTCs in 95 patients. All cases were pathologically confirmed by surgery. Histopathologic characteristics were analyzed for tumor distribution, microcystic changes, fibrosis, and tumor component. We assumed several histopathologic conditions to be the cause of indeterminate or inadequate results of FNAB, including: 1) an uneven tumor distribution, 2) > 30% microcystic changes, 3) > 30% fibrosis, and 4) < 30% tumor component. Ultrasonographic findings of each PTC were evaluated for echotexture (homogeneous or heterogeneous), echogenicity (markedly hypoechoic, hypoechoic, isoechoic, or hyperechoic), and volume of the nodule. We correlated histopathologic characteristics of the PTC with results of the FNAB and ultrasonographic findings. Results: From 95 FNABs, 71 cases (74%) were confirmed with malignancy or suspicious malignancy (PTCs), 21 (22%) had indeterminate results (atypical cells), and three (4%) were negative for malignancy. None of the assumed variables influenced the diagnostic accuracy of FNAB. Tumor distribution and fibrosis were statistically correlated with ultrasonographic findings of the PTCs (p < 0.05). Uneven tumor distribution was related with small tumor volume, and fibrosis over 30% was correlated with homogeneous echotexture, markedly hypoechoic and hypoechoic echogenicity, and small tumor volume (p < 0.05). Conclusion: No histopathologic component was found to correlate with improper results of FNAB in PTCs. In contrast, two histopathologic characteristics, uneven distribution and fibrosis, were correlated with ultrasonographic findings.