Bethesda thyroid

Dr. Pankaj Gupta

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

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

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

Recommended diagnostic categories

1. Non Diagnostic or Unsatisfactory (ND/UNS)

- Cystic fluid only

- Virtually acellular specimen

- Other (obscuring blood, clotting artifacts)


2. Benign

- Consistent with benign follicular nodule

- Consistent with lymphocytic ( Hashimoto’s thyroiditis) in proper clinical context

- Consistent with granulomatous (sub acute) thyroiditis

- Others


3. Atypia of Undetermined significance or Follicular lesion of undermined significance (AUS/FLUS)


4. Follicular neoplasm or Suspicious for Follicular neoplasm (Specify if Hurthle cell or Oncocytic type)


5. Suspicious for malignancy

- Suspicious for Papillary carcinoma

- Suspicious for Medullary carcinoma

- Suspicious for Metastatic carcinoma

- Suspicious for Lymphoma

- Others


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

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

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

• Specimen containing cyst macrophages only are kept under ND/UNS

• Unless specified in report specimen is considered adequate

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

• Other benign categories include Hashimoto thyroiditis, Granulomatous thyroiditis

• Infections, amyloid, black thyroid, reactive changes can be mentioned as descriptive diagnosis

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

• 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)

• 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

• 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

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.

• 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

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

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

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

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Bethesda thyroid