W5L6 - Thyroid FNA Flashcards
Basic Histology of Thyroid Gland
Follicles are lined by uniform cuboidal cells, which synthesise and secrete T3, T4
Hormones are stored with thyroglobulin (“colloid”) in follicles
Active - small follicles
Inactive - distended follicle
Thyroid Nodule: FNAB
The best test
Major purpose is to differentiate malignant from benign disease
Technique:
- US guided 99%, direct 1%
- cyto attended vs non-cyto attended
- non-aspiration vs aspiration
- direct aspiration with or without suction, usually with a 23g needle
- one direction, never multi-directional and no rotation
- speed is the most important factor (i.e. 1, 2, 3 out NOT 1 and 2 and 3 out)
Slide Prep
Air-dried preferred
Lens shaped smears not touching sides (remove excess blood with 19G drawing up needle)
Cyto attended - not necessary to stain all slides on location
Non-cyto attended - dry completely before packaging
Cell blocks
- all suspected neoplasms, previous indeterminate
- separate entire needle pass(es)
Slide Prep - Detecting and Avoiding Artefacts
Formalin vapour artefact
- damages all cells on all smears
- BNF containers for cell blocks or biopsies must be in separate plastic bag from glass slides
Slow air drying artefact
- causes marked cellular enlargement, occurring with fluid or blood-stained samples
- use hair dryer at 30 cm on cool/low heat to dry quickly
Traumatisation artefact
- cells will disrupt if any pressure is used when making smears
- the weight of the glass slide should be the only pressure applied
Ultrasound gel
- obscures cells
- consider using chlorhexidine 0.5% in 70% alcohol instead
Local anaesthetic artefact
- lignocaine toxic to cells
- avoid aspirating the anaesthetic field
Approach to Cytodiagnosis
Presence/amount of thin colloid Cellularity - dominant pattern: sheets vs groups - mixed patterns - repetitive small rounded groups - cytoarchitecture Cell morphology Lymphocytes, fire-flares, giant cells, paravacuolar granules, calcium, debris
New Australian Classification of Thyroid Smears - Non-diagnostic, Benign, Indeterminate
It is non-diagnostic (~10-20%) if: - cyst - insufficient cells - poor preservation - risk of malignancy < 5% It is benign (~40-60%) if: - colloid nodule/MNG - autoimmune thyroiditis - De Quervain thyroiditis - parathyroid cyst - lymph node esp isthmus It is indeterminate (possibly a DDx of 15-20%) if: - colloid nodule vs follicular neoplasm - thyroiditis vs follicular neoplasm - some cysts, miscellaneous (risk of malignancy 5-13%)
New Australian Classification of Thyroid Smears - Suggestive of Follicular Neoplasm, Suspicious of Malignancy
Suggestive of follicular neoplasm (~10%)
- follicular and Hurthle cell neoplasm
- follicular patterned neoplasm w/o clear papillary features (risk of malignancy 21-26%)
Suspicious of malignancy (2-3%)
- must be strongly suggestive of malignancy
- mainly PTC, some MTC, lymphoid lesions, marked pleomorphism
- risk of malignancy 90%
Diseases of the Thyroid
Non-neoplastic - nodular goitre - graves disease - autoimmune thyroiditis - sub acute and Riedel's thyroiditis Neoplastic - benign, malignant
Diseases of the Thyroid - Benign Disease
Makes up 60% of cytology Benign nodules - colloid nodules - nodular colloid goitre with hyperplastic (adenomatoid) nodules - nodules of Grave’s & autoimmune thyroiditis - follicular adenomas Grave's Thyroiditis Benign cysts Others
Colloid Nodules
Not very cellular
Macroscopically shiny, varnish sort of look (like nail polish)
Scattered follicular cells, variable, honeycomb sheets, occasional micro follicles
Cystic macrophages
Types of Thyroiditis
Lymphocytic/Hashimoto’s (autoimmune thyroiditis) - hypothyroidism
Sub-acute - rare, thought to be due to a viral infection
Acute/suppurative - due to bacterial infection
Riedel’s - a rare chronic inflammatory disease characterised by dense fibrosis that replaces normal thyroid parenchyma
Lymphocytic/Hashimoto’s Thyroiditis
Clinically patients present with a goitre/hypothyroidism - fatigue - weight gain - depression - cold intolerance - excessive sleepiness - constipation Radiology - diffusely enlarged thyroid with heterogenous architecture - presence of hypoechoic micronodules - occasional increase blood flow Lab investigations: - thyroid function studies - serology
Lymphocytic/Hashimoto’s Thyroiditis - Cytology
Inflammatory cells - lymphocytes - plasma cells +/- - histiocytes +/- - multinucleated cells +/- Background - blood and scant colloid Epithelial cells: - variable regular follicular cells - Hurthle cells
Graves Disease
Overproduction of thyroid hormones Symptoms: - anxiety and irritability - fine tremor of hands or fingers - weight loss despite normal eating habits - bulging eyes - erectile dysfunction - low TSH levels inc T3/T4
Graves Disease - Cytology
Flat sheets, loose groups
Abundant delicate/foamy cytoplasm
Flame cells – ‘fire flares’ marginal cytoplasmic vacuoles with red-pink frayed edges
Micro follicles and colloid is depleted
