Bethesda System of Thyroid

1. Dr. Pankaj Gupta

2. October 2007 meeting was organized at National
Cancer Institute (NCI), Bethesda, to address the
terminology and other issues in thyroid FNA

3. Idea behind uniform reporting system
• Facilitate effective communication among cytopathologist, radiologist,
endocrinologist and surgeon
• Facilitate Histocytological correlation for thyroid disease
• Facilitate research into epidemiology, molecular biology, pathology and
diagnosis of thyroid diseases
• Allow easy and reliable sharing of data from different laboratories for
national and international collaboration studies

4. Format of report
• Each report begin with six general categories
• Some categories have two alternative names as the consensus was
not reached at NCI conference on single name
• Each categories has implied cancer risk ( ranging from 0 to 3% for
benign categories to virtually 100% for malignant)
• Additional descriptive comments beyond such subcategorization are
optinal and left to discretion of pathologist

5. Recommended diagnostic categories
1. Non Diagnostic or Unsatisfactory (ND/UNS)
- Cystic fluid only
- Virtually acellular specimen
- Other (obscuring blood, clotting artifacts)

6. Recommended diagnostic categories
2. Benign
- Consistent with benign follicular nodule
- Consistent with lymphocytic ( Hashimoto’s thyroiditis)
in proper clinical context
- Consistent with granulomatous (sub acute) thyroiditis
- Others

7. Recommended diagnostic categories
3. Atypia of Undetermined significance or Follicular lesion
of undermined significance (AUS/FLUS)

8. Recommended diagnostic categories
4. Follicular neoplasm or Suspicious for Follicular
neoplasm (Specify if Hurthle cell or Oncocytic type)

9. Recommended diagnostic categories
5. Suspicious for malignancy
- Suspicious for Papillary carcinoma
- Suspicious for Medullary carcinoma
- Suspicious for Metastatic carcinoma
- Suspicious for Lymphoma
- Others

10. Recommended diagnostic categories
6. Malignant
- Papillary thyroid carcinoma
- Poorly differentiated carcinoma
- Medullary thyroid carcinoma
- Undifferentiated ( Anaplastic ) carcinoma
- Squamous cell carcinoma
- Carcinoma with mixed features
- Metastatic carcinoma
- Non Hodgkin lymphoma
- Others

11. CATEGORY I (Non Diagnostic or Unsatisfactory)
Causes of Unsatisfactory smears
- Obscuring blood
- Overly thick smears
- Air drying of alcohol fixed smears
- Inadequate number of follicular cells

12. Criteria for adequacy
• At least six groups of benign follicular cells is required with each
group composed of at least 10 cells.
• Any specimen that contain abundant colloid is considered
adequate
• When a specific diagnosis (e.g. Lymphocytic thyroiditis) can be
given or when there is any atypia specimen is by definition
adequate

13. • Specimen containing cyst macrophages only are kept under
ND/UNS
• Unless specified in report specimen is considered adequate

19. Category II ( Benign)
• An adequate cellular specimen composed of varying proportion of
colloid and benign follicular cells arranged in macro follicles or
macrofollicular fragments are considered as benign follicular
nodule
• If nodule shows significant growth or suspicious radiological
features then, a repeat FNA is considered

20. • Other benign categories include Hashimoto thyroiditis,
Granulomatous thyroiditis
• Infections, amyloid, black thyroid, reactive changes can be
mentioned as descriptive diagnosis

24. Category III ( AUS/ FLUS)
Most common scenarios for this categorization are
• Prominent population of micro follicles in an aspirate that does
not otherwise fulfill the criteria for follicular neoplasm
• Predominance of Hurthle cell in a sparsely cellular smear with
scant colloid
• Interpretation of follicular cell atypia is hindered by air drying or
clotting artifacts

25. • A moderately or markedly cellular smear consisting of exclusive
population of Hurthle cells yet clinical setting suggest a benign
Hurthle cell nodule ( Lymphocytic thyroiditis, Multi nodular goiter)
• There are focal features suggestive of Papillary carcinoma
including nuclear grooves, enlarged nuclei with pale chromatin in
an other wise predominantly benign appearing sample. ( these
can be cyst lining cells)

26. • A minor population of follicular cells may show nuclear
enlargement often accompanied by prominent nucleoli
(radioactive iodine, carbamizole, cystic degeneration or
hemorrhage)
• There is atypical lymphoid infiltrate but degree of atypia is not
sufficient to categorize it as Suspicious for malignancy

27. • It is important that only nodules with atypical undetermined
significance should be placed in this category
• Recognizable benign changes like Hurthle cell change, Black
thyroid, Radiation changes should not be classified as AUS
• A moderate or markedly cellular specimen without any significant
nuclear or architectural atypia does not qualify for AUS

28. Category IV (FN/SFN)
• Purpose of this category is to identify a nodule that might be a
follicular carcinoma and triage it for surgical lobectomy
• Term suspicious for Follicular neoplasm is preferred over Follicular
neoplasm because a significant proportion of cases prove out to be
hyperplastic proliferation of follicular cells, most commonly those
of multi nodular goiter.
• Hallmark of this category is disturbed architecture – Follicular cells
predominantly arranges in micro follicles or trabeculae.

29. • Cytological preparations typically have high cellularity and scant to
absent colloid
• Cellular crowding and overlapping are conspicuous and follicular
cells are usually larger than normal
• Nuclear pleomorphism, and mitosis are uncommon
• Cases that demonstrate nuclear features of Papillary carcinoma are
excluded from this category
• If sample is cellular and mostly macro follicles benign interpretation
is appropriate

33. Category V (Suspicious for malignancy)
• If only 1 or 2 characteristics of malignancy are present, if they are
only focal or if sample is sparsely cellular and a malignant diagnosis
cannot be made with certainty

35. Category VI (Malignant)
• This category is used whenever cytomorphological features are
conclusive for malignancy
• Descriptive comments that follow are used to sub classify
malignancy and to summarize the results of special studies if any

37. DIAGNOSTIC CATEGORY RISK OF MALIGNANCY USUAL MANAGEMENT
ND/ UNS 1-4 % Repeat FNA with ultrasound
guidance
Benign 0-3 % Clinical Follow up
AUS/ FLUS 5-15% Repeat FNA
FN/ SFN 15-30% Surgical lobectomy
Suspicious for Malignancy 60-75% Near total thyroidectomy /
Surgical lobectomy
Malignant 97-99% Near total thyroidectomy