Cystic thyroid nodules after aspiration mimicking malignancy: sonographic characteristics

J Ultrasound Med. 2010 Oct;29(10):1415-21. doi: 10.7863/jum.2010.29.10.1415.


Objective: The purpose of our study was to provide sonographic findings of cystic nodules, which can mimic malignancies, after fine-needle aspiration (FNA) and to determine the differential points from malignancies.

Methods: We retrospectively reviewed the sonographic findings of 33 lesions in 32 patients who had FNA for predominantly cystic nodules or cysts and showed suspicious findings during sonographic follow-up, as well as findings of 47 surgically confirmed papillary thyroid carcinomas (PTCs) in 45 consecutive patients. We evaluated the size, shape, presence of shadowing and a halo, margin, echogenicity, and presence of echogenic dots for each nodule. The final diagnosis of cystic nodules was confirmed by FNA, surgery, or follow-up sonography.

Results: Of the 33 cystic lesions, 31 (94%) were adequate with benign results, and 2 (6%) were inadequate specimens at the initial FNA. There were no malignancies in the cystic nodules at follow-up. The average interval between the initial FNA and suspicious sonographic findings was 26 months (range, 1-92 months). The average size of the suspicious nodules was 0.8 cm (range, 0.3-1.8 cm). Cystic nodules after aspiration were similar to PTCs in their sonographic findings, but the former frequently showed shadowing and a halo (85% versus 21%; P < .0001). With further follow-up, 29 lesions (88%) showed additional decreases in size.

Conclusions: Benign cystic nodules after aspiration can have suspicious malignant features. However, shadowing and a halo associated with malignant features are characteristic findings of cystic nodule shrinkage. Awareness of these findings and correlation with the FNA history can aid in preventing unnecessary FNA.

MeSH terms

  • Biopsy, Fine-Needle
  • Carcinoma, Papillary / diagnostic imaging
  • Cysts / diagnosis
  • Diagnosis, Differential
  • Humans
  • Retrospective Studies
  • Thyroid Neoplasms / diagnostic imaging*
  • Thyroid Nodule / diagnostic imaging*
  • Thyroid Nodule / pathology
  • Ultrasonography