Objective: To determine the value of specific cytopathologic features on fine-needle aspiration biopsies (FNABs) at predicting thyroid malignancy.
Design: Retrospective review of consecutive patients undergoing thyroidectomy between 2005 and 2007 following FNAB of thyroid nodules.
Setting: Two McGill University teaching hospitals in Montreal.
Methods: One hundred forty-seven patients were reviewed and further categorized into two groups (benign vs malignant) based on the final histopathologic diagnosis. The frequency of specific cytopathologic features from the preoperative FNAB samples was recorded for 106 patients from the first hospital and 41 patients from the second.
Results: The presence of atypical cells (30% vs 72%; p = 3.23 x 10(-7)), nuclear grooves (5% vs 23%; p = .002), anisonucleosis (8% vs 36%; p = .00011), variable chromatin staining (10% vs 28%; p = .007), hypochromasia (11% vs 47%; p = 7.19 x 10(-6)), nuclear overlapping/crowding (8% vs 29%; p = .0019), irregular nuclear membranes (15% vs 52%, p = 3.22 x 10(-6)), micronucleoli (15% vs 60%, p = .003), and powdery chromatin (8% vs 47%, p = .004) correlates with an increased risk of malignancy. Alternatively, siderophages (44% vs 23%; p = .007) and honeycomb arrangements (92% vs 60%; p = .012) were more associated with benign processes. HBME-1 staining (n = 53) was positive or focally positive on 61% of the malignant cases (p = .0002), with a specificity of 100%. All biopsies demonstrating intranuclear inclusions, papillary fragments, or atypical architecture were malignant.
Conclusion: Some cytopathologic features are more significantly associated with thyroid malignancy. The cytopathologic features listed in FNAB reports and HBME-1 immunoreactivity are, alone or in combination, additional tools available to the physician to guide management of thyroid nodules.