Thyroid Nodule FNA



Diagnostic categories
Thy 1 - non-diagnostic
(inadequate or where technical artefact precludes interpretation; adequate smears usually contain six or more groups of over 10 thyroid follicular cells, but the balance between cellularity and colloid is more important)
Thy 2 - non-neoplastic
(with the descriptive report documenting the features consistent with a colloid nodule or thyroiditis). Cysts may be classified as Thy2 if benign epithelial cells are present.
Thy 3 - follicular lesion/suspected follicular neoplasm
. Rarely, cases that do not quite fit into Thy2 and Thy 4.
Thy 4 - suspicious of malignancy
(suspicious, but not diagnostic, of papillary, medullary or anaplastic carcinoma, or lymphoma).
Thy 5 - diagnostic of malignancy
(unequivocal features of papillary, medullary or anaplastic carcinoma, lymphoma or metastatic tumour).
Action required
Thy 1 - non-diagnostic
Repeat, unless cyst in which case USS or clinical follow-up may be adequate
Thy 2 - non-neoplastic
Two 3-6 months apart usually exclude malignancy, though one may be enough, and some high risk patients require surgery even with a benign FNA.
Thy 3 - follicular lesion/suspected follicular neoplasm
Usually lobectomy with completion thyroidectomy if malignant.
Thy 4 - suspicious of malignancy
Surgery usually indicated.
Thy 5 - diagnostic of malignancy
Surgery usually indicated.

Summary from Brigham & Women's - Frates et al, Yassa et al


Results of FNA cytology and histology of subsequent surgical specimens
Percentage of initial aspirates in each category; percentage of final aspirates (including repeats); percentage of histological malignancy in patients going for surgery in each category
FNA diagnosis Initial
aspirate
Final
aspirate
Histological
malignancy
Malignancy 5% 5% 97%
Suspicious papillary 8% 9% 60%
Suspicious follicular 8% 9% 28%
Atypical undetermined 6% 4% 24%
Insufficient 13% 7% 10%
No malignancy 60% 66% 0.3%
Likelihood of malignancy of a thyroid nodule
Diagnosis based on histological surgical specimens after suspicious FNA cytology
Gender Women Men
Nodule composition Punctate
calcifications
Coarse or rim
calcifications
No
calcifications
Punctate
calcifications
Coarse or rim
calcifications
No
calcifications
Solitary nodule
Completely solid 32.7 26.1 14.3 47.8 39.9 23.9
Predom. solid 25.2 19.6 10.3 38.7 31.4 17.8
Mixed 15.7 11.9 6.0 25.9 20.3 10.7
Predom. cystic 6.4 4.7 2.3 11.3 8.5 4.2
Comp. cystic 0 0 0 0 0 0
One of multiple nodules
Completely solid 17.9 13.7 7.0 29.1 23.0 12.3
Predom. solid 13.1 9.9 4.9 22.1 17.1 8.9
Mixed 7.7 5.7 2.8 13.6 10.2 5.1
Predom. cystic 3.0 2.2 1.0 5.4 4.0 1.9
Comp. cystic 0 0 0 0 0 0

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