ANATOMY AND HISTOLOGY
• Thyroid glands are located in the anterior part of neck
in front of trachea and inferior to larynx.
• The gland is composed of two lobes, which are
connected by central part known as isthmus.
• The thyroid gland is covered by thick fibrous septae.
• The fibroconnective tissue has divided the lobes into
multiple smaller lobules.
• Follicles are the basic structural unit of thyroid gland.
• Each follicle contains homogenous eosinophilic colloid
• Follicles are lined by low cuboidal to columnar cells.
• Thyroid follicular cells liberate tri-iodothyronine (T3 ) and
thyroxine (T4 ) hormone.
• Due to some unknown reason, thyroid follicular cell may
undergo Hurthle cell change.
• These are large cells with abundant eosinophilic cytoplasm
and central round nuclei.
• Parafollicular cells are present in the periphery of the follicles
as small cluster.
• These cells are three to four times larger than the follicular
• They have pale moderate amount of cytoplasm with central
• Parafollicular cells secrete calcitonin hormone that takes
important role in calcium homeostasis.
• Calcitonin hormone inhibits bone resorption by osteoclasts
and, thereby helps to lower the calcium concentrations in
FINE NEEDLE ASPIRATION OF
CYTOLOGY OF THE THYROID
INDICATIONS OF FINE NEEDLE ASPIRATION OF
• Any palpable nodule of thyroid
• Thyroid nodule of less than 10 mm diameter with clinical or
suspicious features in USG (ultrasonography)
• Predominantly solid nodule in USG
• USG guided FNAC could be done in solid area of a cystic
nodule and from a nonpalpable nodule.
• The patient should be kept in supine position with a small
pillow under his neck to make the thyroid region prominent.
• The technique of FNAC in the thyroid gland is essentially
• After cleaning the area of thyroid, the gland is hold in between
the two fingers so that the thyroid will be prominent.
• Depending on the aspirator’s choice, FNAC or nonsuction fine
needle sampling (FNS) can be done.
• As the thyroid is a vascular organ so FNS is preferable in
small swelling of the thyroid gland.
• However, in case of a cystic lesion, FNAC is preferable as
there is a chance of spillage by FNS technique.
• It is recommended to do three to five passes of needle in each
• Multiple smears should be made immediately from the
aspirated material and both air dried smear and alcohol fixed
smears should be kept.
• If necessary, the material should be taken for cell block and
other ancillary investigations.
• The thyroid nodule is hold in between two fingers and gentle
suction is done.
• FNS is preferable in thyroid as the material is free from blood.
• Thyroid swelling is hold tightly in between the two fingers so
that the thyroid will be prominent.
• Now, the needle is moved gently to and fro within the lesion.
• Material comes to the needle hub with the help of capillary
• The needle is gently withdrawn and the syringe is attached
with the hub.
• The material in the needle is spread on the slide.
• The FNAC material can also be collected for cell
block and flow cytometry to do ancillary technique.
a) Colloid: Gross appearance of colloid is thick to thin
• The MGG stained cytology smear shows a pale blue
pale blue thin colloid material
b) Thyroid follicular cells:
• Follicular cells are present in small clusters and
• The cells are round with scanty cytoplasm
and round monomorphic nucleus.
• Nuclear chromatin is homogeneously
c) Foam cells : The foam cells show abundant foamy
cytoplasm with small monomorphic nucleus.
1) COLLOID GOITER –
a) Nodular colloid goiter is the commonest diseases of
Cytology of nodular goiter
• Abundant colloid
• Discrete or flat sheet of thyroid follicular cells
nodular goiter in a young female
Abundant thick and thin colloid along
with scattered benign thyroid follicular
cells in colloid goiter
b) Adenomatoid hyperplasia or hyperplastic nodules
• Cellular smear
• Dissociated and microfollicular arrangement
• Hurthle cells
• Foamy macrophages
• Scanty colloid
Multiple follicles and thin colloid
c) Diffuse toxic goiter (Grave’s disease)
• Scanty watery colloid
• Enlarged cell with vacuolated cytoplasm
• Prominent nucleoli
• Fire flares appearance
a) Acute Thyroiditis- Acute thyroiditis patient presents
with fever, tachycardia, and sudden painful enlargement
• Polymorphs and lymphocytes
• Degenerated thyroid follicular cells.
b) Subacute Granulomatous Thyroiditis
• Dirty background formed by cellular debris and
• Epithelioid cell granulomas
• Multinucleated giant cells
• Lymphocytes and plasma cells
• Benign thyroid follicular cells with paravacuolar