Fine needle biopsy of thyroid nodules: the importance of technique

Fine needle biopsy (FNB) is the most accurate method available for the investigation of single thyroid nodules. The exact technique employed, however, varies considerably among clinicians: in our institution the incidence of 'inadequate' specimens produced ranges from only 13 to 62%, depending on the individual performing the biopsy. In a prospective in vivo study, a variety of biopsy techniques employing different gauge needles and differing numbers of passes with and without aspiration were assessed with respect to the quality of cytological specimen produced. Criteria assessed included the number of cells or sheets of cells, cell clumping, blood contamination, amount of colloid, and overall slide quality. Samples obtained with a 21 gauge needle without aspiration consistently gave best individual cell morphology. On the other hand, samples obtained with a 23 gauge needle with five aspirated passes through the nodule gave the highest yield of cells with an acceptable minimal increase in the degree of blood contamination and cell clumping. In order to achieve consistent yields from FNB of thyroid nodules, a combination of these two techniques is recommended.