Background: The need to perform fine-needle aspiration biopsy (TFNAB) on subcentimeter thyroid nodules is less clear than for larger nodules. We compared the ultrasonographic features of thyroid nodules less than and greater than one centimeter and correlated this information with the cytological results for TFNAB and the final histopathological diagnosis in selected patients.
Methods: We evaluated 520 thyroid nodules (247 subcentimeter [group 1], 273 supracentimeter [group 2]) in 426 patients. Ultrasonography-guided fine-needle aspiration biopsy was performed on all nodules. Surgery was recommended for patients with TFNAB results that were read as malignant or suspicious. The results of ultrasonography, TFNAB, and histopathology were compared between the groups.
Results: Out of 426 patients, 337 had one nodule, 84 had two, and five had three. There was indeterminate cytology in 20 cases, 10 from each group. Inadequate cytology was obtained in 41/247 (16.6%) nodules in group 1 and 61/273 (22.3%) nodules in group 2, and the difference in rate was not significant (p = 0.067). The malignancy rate as determined by TFNAB was 4.9% in group 1 and 1.5% in group 2 (p < 0.025). In patients who underwent surgery for thyroid nodules the malignancy rate was 6% in group 1 and 2.9% in group 2 (p = 0.08). Hypoechoic pattern, microcalcification, and a long axis/short axis ratio (LA/SA) of < 1.5 were associated with malignancy in subcentimeter thyroid nodules (group 1), while only a hypoechoic pattern was associated with malignancy in supracentimeter thyroid nodules (group 2).
Conclusions: The incidence of cancer in thyroid nodules < 1 cm does not appear to be lower than in larger nodules and may even be higher. Physicians should consider obtaining biopsy samples from subcentimeter hypoechoic nodules that contain microcalcification and have a relatively round shape (LA/SA < 1.5).