The frequency of malignant disease in cytological group of suspected cancer (ultrasound-guided fine-needle aspiration biopsy of nonpalpable thyroid nodules)

Background. Fine-needle aspiration biopsy is the most important procedure for differentiating benign thyroid nodules from malignant ones. Traditionally, findings of fine-needle aspiration biopsy are divided into four categories: nondiagnostic, benign lesions, suspected cancer, and malignant lesions. Group suspicious for cancer largely involves follicular neoplasms as well as lesions with cytological features of malignancy.
Objective. The purpose of this study was to establish the value of ultrasound-guided fine-needle aspiration biopsy in the diagnosis of nonpalpable thyroid cancer and to assess the frequency of malignant disease in the group of suspected cancer.
Patients and methods. A total of 184 patients with nonpalpable thyroid nodules (less than 1.5 cm in diameter) were examined by means of ultrasound-guided fine-needle aspiration biopsy. Patients were included in the study based on sonographic findings implicating possible malignant nature of nodules.
Results. During 1997–2002, 204 ultrasound-guided fine-needle aspiration biopsies of thyroid nodules were performed; findings were nondiagnostic in 5.9% of cases. In 59.8% of cases, cytological examination revealed benign lesions; in 11.8%, suspected cancer; and in 22.5%, malignant lesions. Eighty-five patients underwent subsequent surgery with histological examination of specimens obtained. In 45 cases, cytological diagnosis of malignant or suspected thyroid cancer was confirmed by histological examination after surgery.
Conclusion. We conclude that ultrasound-guided fine-needle aspiration biopsy has a high accuracy in the diagnostic evaluation of nonpalpable thyroid nodule with cytological features of malignancy. However, fineneedle aspiration biopsy is not effective diagnostic method for differentiating benign thyroid nodules from malignant ones in follicular neoplasm group.