This document provides information about fine needle aspiration cytology (FNAC) of the thyroid. It discusses that FNAC is a simple, quick, and inexpensive technique used to distinguish between benign and malignant thyroid lesions. FNAC has high sensitivity and specificity and is the investigation of choice for evaluating thyroid nodules. The document outlines the equipment, technique, indications, contraindications, complications, limitations of FNAC, and the Bethesda system for classifying thyroid cytopathology results and recommended clinical management.

1. FNAC THYROID

2. INTRODUCTION
• Fine Needle Aspiration Cytology(FNAC) is a technique whereby cells are obtained
from a lesion using a thin bore needle and smears are made for cytopathological
diagnosis.
• This technique is based on the fact that tumor cells are less cohesive and are easily
aspirated.
• It is a simple,quick and inexpensive method and is usually performed as an
outpatient procedure.
• Used in the diagnosis of thyroid nodules,breast lumps,liver disease,subcutaneous
soft tissue mass,oral and salivary gland lesions.

3. FNAC THYROID
• FNAC is the investigation of choice for thyroid Nodules.
• As FNAC distinguishes between benign and malignant lesions quite
effectively,its use has markedly decreased the number of unnecessary thyroid
surgeries.
• USG guidance increases the accuracy of FNAC
• Sensitivity: 93.4% ; specificity: 74.9%

4. EQUIPMENTS
• NEEDLE: 22-23 gauge needle; 1.5 inch length
• SYRINGE: 20 ml
• GLASS SLIDES
• FIXATIVES: 95% ethanol
• STAINS: Papanicolaou stain, hematoxylin&eosin stain,Romanowsky stain
• MICROSCOPE

5. TECHNIQUE
• After sterilizing the skin over the palpable mass, 23 gauge needle is introduced
through the skin into the mass.
• Having confirmed the position of the needle within the mass,negative pressure
should be created within the syringe by pulling the plunger.
• The needle should be moved back and froth through the mass in different rotational
directions
• Suction should be maintained throughout the process. By this method,the needle
can cut loose many small pieces of tissue that can be aspirated
• To and fro strokes should be repeated 6-8 times.

6. • After the aspirations ,all suction should be released before removing the
needle from the mass by allowing the syringe plunger to return gently to its
resting position.
• The needle is then withdrawn gently from the mass and a firm pressure
should be applied over the site to limit hematoma formation

9. INDICATIONS OF FNA IN THYROID
LESIONS
1. Evaluation of solitary thyroid nodules (to distinguish benign from
malignant)
2. Evaluation of diffuse thyroid lesions (to distinguish
inflammatory/autoimmune lesions from nodular goiter)
3. Confirmation and categorisation of clinically obvious thyroid malignancy
4. For prognosis

10. CONTRAINDICATIONS
• No contraindications

11. COMPLICATIONS
• Minor hematoma
• Rarely, puncture of the trachea, carotid artery or jugular vein

12. LIMITATIONS
• Cannot differentiate between follicular adenoma and carcinoma
• Needling may convert hot nodule to a cold nodule and vice versa therefore all non-
invasive investigations should be done before FNA
• False positive results:
Hashimoto’s
Graves’s
Toxic nodules

13. BETHESDA SYSTEM
1.NON-DIAGNOSTIC OR UNSATISFACTORY:
• Cyst fluid only
• Virtually acellular specimen
2.BENIGN
• Consistent with benign follicular nodule- adematoid nodule,colloid nodule
• Consistent with lymphocytic (hashimoto’s) thyroiditis
• Consistent with granulomatous (subacute) thyroiditis

14. 3. ATYPIA OF UNDETERMINED SIGNIFICANCE
4.FOLLICULAR NEOPLASM OR SUSPICIOUS FOR FOLLICULAR
NEOPLASM
5.SUSPICIOUS FOR MALIGNANCY

15. 6.MALIGNANT
• Papillary thyroid carcinoma.
• Medullary thyroid carcinoma.
• Undifferentiated (anaplastic) carcinoma
• Squamous cell carcinoma
• Metastatic carcinoma
• Non-Hodgkins lymphoma

16. COLLOID NODULE

17. SUBACUTE THYROIDITIS

18. HASHIMOTO’S THYROIDITIS

19. PAPILLARY CARCINOMA

22. FOLLICULAR CARCINOMA

23. • FNAC cannot differentiate between follicular adenoma and carcinoma as it
depends upon capsular and angioinversion
• Options in follicular ca: Frozen section biopsy

24. MEDULLARY CARCINOMA

25. ANAPLASTIC CARCINOMA

26. BETHESDA SYSTEM FOR REPORTING
THYROID CYTOPATHOLOGY
DIAGNOSTIC CATEGORIES RECOMMENDED
MANAGEMENTS
RISK OF MALIGNANCY
Nondiagnostic or unsatisfactory Repeat FNA with USG guidance -
Benign Clinical followup & repeat FNA if the
lesion increases in size
0-3%
Atypia of undetermined significance or Follicular
lesion of undetermined significance
Repeat FNA 5-15%
Follicular neoplasm or suspicious for a follicular
neoplasm
surgical lobectomy 15-30%
Suspicious for malignancy Near total thyroidectomy 60-75%
Malignant Total thyroidectomy 97-99%

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