Value of thyroid FNA test?

To meet diagnostic criteria, each slide must contain ≥ 6 groups of follicular cells, with each group having ≥ 10 cells. However, this quantitative criterion will be waived for the following 3 cases:
The specimen contains atypical follicular cells, even if the number is small, it is still considered to meet the diagnostic criteria. For example, a slide containing only a group of follicular cells forming a papillary structure with the morphological features of papillary thyroid carcinoma is sufficient to be classified as group VI. Specimens containing high levels of lymphocytes (from Hashimoto's thyroiditis), polymorphonuclear leukocytes (acute abscessed thyroiditis), epithelial cells, and macrophages (granulomatous thyroiditis) were still considered diagnostic criteria. diagnosis (group II) even though only few follicular cells were present. A specimen containing all the solid thyroid colloid (from a multinodular thyroid aneurysm) was also considered to meet the diagnostic criteria (group II) even though it contained few follicular cells. The number of aspiration cases falling into group I accounts for about 10-30%, depending on each cytological labor; but once the rate is more than 20%, it is necessary to check the quality of technical stitches (aspiration, fixation and dyeing...) to achieve optimal results. Management attitude for group I is to repeat FNAC for the second time after 3 months under ultrasound guidance; about 60% of second FNAC meet diagnostic criteria.
5.2 Group II - Benign Thyroid pathologies with benign cytological findings are most commonly polygranulomatous thyroiditis, Hashimoto's thyroiditis, granulomatous thyroiditis and acute thyroiditis.
5.3 Group III - Atypia of Undetermined Significance Classified in this group are specimens containing a number of abnormal cells that are not known to be benign or malignant (including follicular cells). thyroid and other cell types) but do not meet the criteria for group IV, V or VI; The patient will be asked to repeat the FNAC after 3 months. The risk of malignancy in group III is 5-15%.
It is necessary to avoid overusing diagnosis of group III because in many cases, atypical cells are caused by technical errors in specimen preparation (slow fixation, drying,...). The prevalence of group III should not exceed 7% of all FNAC cases.
The characteristics of the specimens that can be classified into group III are very diverse, including: (Figure 9)
Beside the 2-dimensional flat clusters, there are small thyroid cysts with equal proportions (50/50); Small thyroid cysts can also be seen in polynodular aneurysms, but usually in less than 10%). The smear is poor in cells but mostly small thyroid cysts. The smear is poor in cells but full of Hürthle cells. The smear is almost entirely benign, but there are few cells with scattered grooved nuclei. The slide contains many lymphocytes and plasma cells with some lymphocytes with atypical nuclei. Cellular abnormalities cannot be classified, eg few cells with large nuclei, enlarged nucleoli. 5.4 Group IV - Suspicious for follicular neoplasm The macroscopic and microscopic images of cystic carcinoma and benign cystic thyroid tumor can be identical; The malignancy of the tumor is determined only by the invasion of tumor cells into the capsule or blood vessels, which cannot be evaluated on cytological specimens.
Therefore, FNAC can only diagnose a suspected nodular lesion of the thyroid gland called a cystic thyroid nodule, but cannot differentiate between benign and malignant. Group IV patients with a risk of malignancy of 15-30%, will undergo a corresponding lobectomy.
5.5 Group V - Suspicious for malignancy accounts for about 2.4-7.9% of thyroid FNAC cases. The cytology specimen of patient
in this group still has normal follicular cells, but some cells have
features that are suspicious of thyroid cancer; Thus, the quantity is not enough to be classified in group VI. Particularly, cases of suspected follicular thyroid tumor or Hrthle cell tumor are not included in this group, but in group IV. Patients with group V have a risk of malignancy from 60-75%, will be operated with cryosection to decide whether to remove only 1 thyroid lobe or to remove the thyroid gland nearly completely.
Suspected papillary thyroid carcinoma Aspiration cytology containing honeycomb-shaped clusters of normal follicular cells; interspersed with a few cells with large oval nuclei, slightly pale, grooved but often do not create papillary structure.
In Hashimoto's thyroiditis and polygranulomatous thyroiditis, some Hürthle cells may have large oval and grooved nuclei, but no inclusions in the nucleus; Therefore, if nodules are seen, papillary thyroid carcinoma should be suspected. (Figure 12)
Suspect medullary thyroid carcinoma when on the slide there are several relatively discrete groups of cells with a high nuclear/cytoplasmic ratio, lateral nuclei, and a slightly salt-and-pepper appearance. The slide matrix may contain several small clusters of amorphous material, whether amyloid or colloid. Suspect thyroid lymphoma when the specimen contains a relatively uniform number of lymphocytes of relatively uniform size and atypical nuclei, in addition to clusters of normal follicular cells. Suspected malignancy, unspecified when the slide contains a few scattered cells, suspected malignancy but cannot be determined to be primary thyroid or metastatic. 5.6 Group VI - Malignant Thyroid diseases with cytological malignancy include papillary thyroid carcinoma, poorly differentiated thyroid carcinoma, undifferentiated thyroid carcinoma, medullary thyroid carcinoma, lymphoma and Carcinomas from elsewhere have metastasized to the thyroid gland. Group VI accounts for about 4-8% of thyroid FNAC cases, the vast majority of which are papillary thyroid carcinomas. Patients with group VI have a malignancy risk of 97-99% and will undergo a total thyroidectomy. Papillary thyroid carcinoma: Papillary thyroid carcinoma is the most common type of follicular cell carcinoma, accounting for 60-80% of primary thyroid cancers. The average age of disease is 40 years old, however, tumors can occur at any age, including children; Females are more susceptible to the disease than males. Fine-needle aspiration cytology has the following features: (Figures 4, 5)
Tumor cells form a 2-dimensional single-layer papillary structure or a 3-dimensional papillary structure containing a vascular axis; however, 3-dimensional papillae are relatively uncommon. Tumor cells have large oval nuclei, light colored superimposed on each other, nuclei have grooves and inclusion bodies. These nuclear features can be found relatively easily throughout the specimen. In addition, squamous tumor cells (with dense cytoplasm), polymorphonuclear macrophages (macrophage origin), zigzag solid colloids, and psammoma bodies (found in 4-20% of cases) can also be seen. papillary thyroid carcinoma).