CHICAGO — Solid thyroid nodules smaller than 1 cm in diameter tend to carry a greater risk of papillary carcinoma than do larger nodules, Dr. Nagesh Ragavendra reported at the annual meeting of the Radiological Society of North America.
The results of this study using fine-needle nonaspiration need to be confirmed in larger investigations as the study was too small to prove statistical significance. But the trend was marked, Dr. Ragavendra said.
The risk was 16% for thyroid nodules 1 cm or less in diameter compared with 8% for nodules 1.1 cm or more.
Surprisingly, the study also found that capsular invasion is relatively common in solid thyroid nodules, said Dr. Ragavendra, professor of radiology and chief of the ultrasound section at the University of California at Los Angeles. Five of the larger-sized nodules had capsular invasion; two had nodal metastases.
Biopsies were performed under ultrasound guidance on 598 focal thyroid nodules in 466 consecutive patients using the fine-needle nonaspiration technique with on-site cytologic examination.
With this technique, cells are extracted with a 25-gauge needle that is repeatedly and rapidly advanced into and withdrawn from the nodule. The needle is not connected to external suction, as is the case with traditional fine-needle aspiration.
Neither technique has proved superior in the cytopathologic studies of thyroid nodules. But it is suggested that fine-needle nonaspiration provides specimens with larger numbers of cells and better preserved cytomorphology, Dr. Ragavendra said.
The sample tends to be less blood tinged with nonaspiration than with aspiration fine-needle biopsy, Dr. Ragavendra added. Further, nonaspiration allows continuous monitoring of the position of the needle tip, thus ensuring proper sampling of the area of interest.
Of the 511 nodules that were 1.1 cm in diameter or larger, histology revealed that 448 (88%) were benign, 39 (8%) were papillary carcinoma, and 24 (5%) were other tumors.
Of the 87 nodules 1 cm or less, 67 (77%) were benign, 14 (16%) were papillary carcinoma, and 6 (7%) were other tumors.
The findings of the investigation do not settle the long-standing debate as to which thyroid nodules should be biopsied. But those with some cystic components tend to be benign, Dr. Ragavendra said. At UCLA, all solid nodules, whether hypoechoic or isoechoic, are candidates for fine-needle biopsy.
