Ultrasound helps reveal vascular patterns in thyroid cancer

Thyroid nodules with dominant central vascularization have a greater chance of being malignant. The vascularization of thyroid nodules can be a complementary criterion in indication of the nodule for fine-needle aspiration, according to studies presented at the 2005 European Congress of Radiology meeting.

Dr. Maria Cristina Chammas and colleagues from the Medical University of São Paulo in Brazil evaluated 177 nodules by B-mode scanning, power Doppler, and spectral analysis. They related the results to the cytological findings of ultrasound-guided fine-needle aspiration.

Nodular analysis with color Doppler was classified in five vascular patterns:

• I: no vascularization

• II: perilesional vascularization

• III: perilesional vascularization greater than or equal to central vascularization

• IV: central vascularization greater than perilesional vascularization

• V: only central vascularization

Spectral analysis considered the resistive index (RI), and univariate and multivariate logistic regression analysis were performed.

The echogenicity parameter did not present significant statistical association at the univariate analysis. Only at the multivariate analysis was it really identified as significant.

Two malignant nodules showed pattern III, six showed pattern IV, and five showed pattern V. These results suggest that the incidence of malignancy is larger where central vascularization is predominant. This parameter showed statistically significant correlation with cytological results, according to Chammas, who presented the study at the 2005 European Congress of Radiology.

Spectral analysis demonstrated that nodules with an RI greater than 0.77 are at high risk of malignancy. The multivariate analysis showed that to select malignant nodules, the vascular patterns and RI are enough and significant.

The nodules with high risk showed patterns IV and V, independent of RI. The nodules with other vascular patterns (II/ III) demonstrated high risk when the RI was greater than 0.77. The sensitivity of this model was 92.3%, and specificity was 88%.

Dr. Rafal Z. Slapa and colleagues from the Center of Oncology in Warsaw used volume-rendered 3D power Doppler to establish features characteristic for thyroid carcinoma. They presented three conclusions at the ECR:

• Papillary thyroid carcinoma can present with different patterns of vessels - in most cases peripheral-central and only rarely peripheral or central.

• There is a large overlap of vascularity patterns between papillary carcinomas and benign nodules.

• Thyroid nodule vascularization can be used in conjuction with other criteria to determine the need for fine-needle aspiration.

Slapa and colleagues evaluated 57 thyroid nodules (10 papillary thyroid carcinomas and 47 benign). A dedicated 3D ultrasound machine with automatic linear transducer was applied, and vessel configuration was evaluated interactively in volume mode within a thin slab of tissue. The pattern, regularity, and density of vessels were evaluated.

Three cancers had no central vessels, while five had a few central vessels with a peripheral-central pattern. Vessels with spoke-and-wheel alignment were observed in six cancers.

In one cancer, chaotic vessels were observed with a central pattern. This configuration was not observed in benign nodules. In one follicular-type papillary cancer that was devoid of classical B-mode suspicious features, moderately increased peripheral-central vessels with spoke-and-wheel alignment were the only features suggesting fine-needle aspiration. Vessels with spoke-and-wheel alignment were observed in 82% of benign nodules.

In another study, Dr. Cristina Avigo and colleagues from the University of Brescia in Italy analyzed the follow-up of patients with a thyroid nodule and an inadequate cytologic diagnosis. They determined that ultrasound follow-up is necessary.

During a four-year period, researchers subjected 93 patients to fine-needle aspiration cytology of a thyroid nodule, in two sessions (at least one month apart) with inadequate cytologic diagnosis. They were followed up by ultrasound periodically, for an average of 24 months.

Eighty nodules remained unchanged in size and structure. Of the 13 that increased in volume, nine were submitted to surgical operation and four to fine-needle aspiration cytology repetitions (all four were benign).

Surgery revealed four malignancies: one follicular carcinoma, two papillary carcinomas, and one medullar carcinoma.

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