Intranuclear cytoplasmic inclusions in cytologically suspicious or malignant thyroid nodules: identification and correlation with echogenicity and size of the nodules.

Intranuclear inclusions (ICI) represent one cytological feature suggestive of malignancy. The aims of this study are (1) to correlate ICI with size and echogenicity of the thyroid nodules that, at fine-needle aspiration cytology (FNAC), are suspiciously malignant (THY4) or malignant (THY5); and (2) to ascertain whether ICI alone or combined with some ultrasonography (US) characteristics would help in predicting malignancy. We studied 90 consecutive thyroid nodules (THY4 n = 60 or THY5 n = 30) from 90 patients, who subsequently underwent thyroidectomy. Prior to thyroidectomy, all 90 nodules were examined by the US-guided FNAC. A cytology/histology correlation was performed. The results showed that 70 nodules were cancerous (82.2 %, THY4 = 73.3 %, THY5 = 100 %). ICI positive (ICI+) were 53/90 nodules (THY4 = 48.3 %, THY5 = 80.0 %), of which three (all THY4) were benign. The maximum diameter was smaller in the 53 ICI +ve than in the 37 ICI -ve nodules (14.2 ± 5.4 vs. 20.0 ± 9.4 mm, P = 0.0001; median volume 1.32 vs. 4.03 ml). In the THY4 smaller hypoechoic nodules, malignancy rate was 95 % with greater probability to detect ICI compared with non-hypoechoic nodules of >20 mm in maximum diameter (31 (75.6 %) vs. 4 (23.5 %), P = 0.0002). Based on the results, we conclude that ICI detection is associated with relatively smaller size and hypoechoic appearance in THY4 or THY5 nodules. In the THY4 nodules, when coupled with these US characteristics, ICI identification selects lesions with high chances of malignancy.