Fine-needle aspiration uses finer needles (21–27 gauges)
than the large-bore needles of large-needle aspiration (14
gauge). Recently introduced CNB devices have a smaller
bore (usually 18–21 gauge) and spring-activated needles
(18, 44, 45). Large-needle biopsy, performed without US
guidance with a large-bore needle, is not recommended for
The proper CNB needle conditions for thyroid nodules are
the following. First, the entire length of needle should not
exceed 10 cm because the thyroid gland is a superficial
organ. Second, needle thickness, especially inner diameter,
determines the thickness of the specimen. However, there
is still no evidence supporting the choice of needle gauge.
Some studies report the use of 16–22-gauge needles (18,
21, 45-47). Although the use of 18–21-gauge needles is
universal for thyroid nodules, 18-gauge needles have been
mainly used in Korea (18, 19, 48-50). The thinner the
needle, the less damage to normal tissue but the lower the
amount of tissue obtained. CNB needles for thyroid nodules
typically have the following characteristics: diameter,
18–21 gauge; needle length, 6–10 cm; excursion length,
1.1–2.0 cm. However, there is no evidence regarding the
relationship between needle thickness, complication rate
and diagnostic accuracy. Finally, the length of the stylet,
namely, the penetration length, can be selected according
to the size of nodule and is usually 1–2 cm.
Core needle biopsy needles are composed of two needles,
the stylet and the cutting cannula (Fig. 1) (18, 44). The
stylet or inner needle has an approximately 2-mm-long
sharply sloped tip to penetrate tissue and a specimen notch
for holding the sampled tissue. The cutting cannula or the
outer blade is the outer component of the CNB needle and
plays a role in cutting the tissue and placing it on the
specimen notch. CNB needles are divided into two types
according to the mechanism of action: automated and
semi-automated. The automated needle is called a doubleaction
needle because both inner and outer needles are
spring-activated. This type of needle fires the stylet via a
spring action that can more easily penetrate hard tissue.
However, it may be more prone to adjacent tissue damage.
The semi-automated needle is called a single-action
needle because the spring activates just once: the stylet
is manually introduced, followed by the spring-activated
needle. The semi-automated needle enables a relatively safe
procedure, despite the presence of a risky aspect because
operators manually push the stylet into the tissue. There
are various kinds of spring power. Although a device with
a strong spring can better penetrate hard tissues such as
calcifications or fibrosis, it has higher potential for injury
of normal tissue or vessels. The amount of tissue obtained
depends on the needle thickness and the length of the
specimen notch (51).
The guiding needle or coaxial needle is a separate needle
that provides assistance and easy intraneedle passage of the
core needle to the target. It provides a clear path to work
through when performing multiple biopsies in the same
area and can improve accuracy and efficiency. However, the
needle tract is greater because the size is larger than that
of the corresponding biopsy needles.
CNB needle in the nodule
Core of tissue including normal thyroid ,Nodule and the nodule capsule of a microfollicular neoplasm.
Modern CNB devices, particularly 18–21-gauge, springactivated,
core needles, are recommended for the procedure.