CYTOMORPHOLOGIC FEATURES OF THYROID LESIONS

Prof. Dr. İlkser Akpolat, F.I.A.C

Acıbadem University

School of Medicine

PLAN

• General approach to the thyroid fine needle aspiration (FNA) evaluation

• Basic microscopic findings

• The role of basic microscopic findings in the differential diagnosis.

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Cellularity• Low / high

• Cell type• Variable cell types /uniform cells

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios+

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Cell type• Variable cell types /uniform cells

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

BENIGN FOLLICULAR NODULE (BFN)/NEOPLASM

ABUNDANT COLLOID SCANT COLLOID

BFN/NEOPLASM

WATERY COLLOID DENSE COLLOID

WATERY COLLOID

• Watery colloid can be indistinguishable from serum.

• The presence of thyroid follicle cells favors colloid.

WATERY COLLOID

• Colloid can be lost from the glass slide during processing

• Colloid is better retained on PAP stained slides

• But it is easier to see on Romanowsky-stained slides

DENSE COLLOID

• More frequent in neoplasms

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Cell type• Variable cell types /uniform cells

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

BFN/ NEOPLASM

LOW CELLULARITY HIGH CELLULARITY

CELLULARITY

– Depends on skill of the aspirator

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Cell type• Variable cell types /uniform cells

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

BFN/NEOPLASM

HETEROGENEOUS CELLS UNIFORM CELLS

Uniform cells, Hurthle Cells (>%75) To diagnose a follicular neoplasma as oncocytic type more than 75% of follicular cells should be oncocytic

Uniform cells carrying papillary carcinoma

nuclear features

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Cell type• Variable cell types /uniform cells

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

BFN/ NEOPLASM

WELL ORDERED SHEETS DISORDERED ARRENGEMENT

Disordered and overlapped thyroid follicular cells from a

papillary carcinoma.

Follicle size

Follicle size is a key factor in assessing follicular lesions

– Large follicules;

• Usually correlate with goiter, thyroiditis, sometimes with adenomas

• But rarely if ever with follicular carcinoma

– Microfollicules;

• Can occur in any follicular lesion

• But are more numerous in neoplasm

BFN/NEOPLASM

MACROFOLLICULES MICROFOLLICULES

Microfollicles are composed of 6-12 cells and they are rosette or ringed shaped. Can be singly or or occur in repeating patterns within groups of cells.

Microfollicullar complexes; are crowded 3-dimensional, syncytial-like aggregates of microfollicles. They are characteristic for follicular neoplasm, but not specific.

BFN/NEOPLASM

HETEROGENOUS FOLLICLES MICROFOLLICULAR PATTERN

BFN/NEOPLASM

PSEUDOPAPILLAE TRUE PAPILLAE

PAPILLARY STRUCTURESTwo types of papillary structures are important

for papillary thyroid carcinoma diagnosis.

• True Papillae

• are considered pathognomonic for papillary thyroid cancer (PTC)

• Caps

• Probably represent tips of papilla

TRUE PAPILLARY STRUCTURES• Uncommon

• Pseudopapillae can mimic true papillae

• The structure of true papillae is also important.

• Short and nonbranching true papillae usually can occur in many diseases

• Goiters, Hyperplasia , Adenoma, Pregnancy, Thyroiditis, Folicular neoplasia, Medullary carcinoma

True Papillae: pathognomonic form

Branching, 3-dimensional, finger-like projections with

fibrovascular cores

Frequent branching

Avascular, 3-dimensional, rounded, dome shaped aggregates of cells known as “caps”

Caps

CELLULAR SWIRLS

are concentrically organized aggregates

of tumor cells

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Cell type• Variable cell types /uniform cells

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

NUCLEAR FEATURESRound; benign, follicular neoplasia Oval, PTC

Medullary Carcinoma

Spindle cells Plasmacytoid cells

Oval and spindle cells can be present in Cystic lesions. Nuclear/cytoplasmic ratio is normal or low . Nuclear crowding or overlapping is not significant .

BFN/NEOPLASM

Nuclear membrane is smooth Nuclear membrane irregularity

Nuclear Membrane Irregularity

– Nuclear grooves (irregular folds)

– Intranuclear pseudoinclusion (cytoplasmic invaginations (INCIs) )

Nuclear Membrane Irregularity

– Nuclear grooves (irregular folds)

• Are key diagnostic features (most cells, most fields)

• Some papillary carcinomas don’t have nuclear grooves

• Some benign and other malign lesions may have nuclear grooves (focal)

A grooved nucleus should have a deep longitudinal fold, like a coffee bean. But can be as irregular and lobulated as a piece of popcorn.

Nuclear GrooveMalignancies

• Papillary thyroid Ca

• Medullary thyroid Ca

• Hürthle Cell Neoplasia

Benign lesions

• Cystic lesion

• Lymphocytic thyroiditis

Cystic lesions

– Atypical cyst-lining cells can have nuclear grooves, prominent nucleoli, elongated nucleus and cytoplasm

– If these are present in a predominantly benign sample, can be diagnosed as AUS.

– If these changes are worrisome and diffuse, can be diagnosed as suspicious for PTC.

Lymphocytic thyroiditis

– Cells may show focal mild atypia. Atypical cells can have nuclear enlargement, grooves and chromatin clearing

– If there is cytomorphologic evidence of LT,

• the diagnostic threshold for PTC should be rised slightly

– If the diagnosis of LT is not definite,

• depending on degree of nuclear atypia, you can diagnose as AUS or suspicious for malignancy.

Nuclear Membrane Irregularity: INCIs

• One real INCI is a recommendation for surgery.

• Nuclear membrane encloses a portion of cytoplasm

Intranucler Cytoplasmic Invaginations (INCIs)

• PTC, % 50-100

• Other malignancies: Medullary thyroid Ca, Poorly differentiated Ca , Anaplastic (undifferentiated) Thyroid Ca

• Benign lesions: Goiter, Follicular Adenoma, Lymphocytic thyroiditis

INCIsCompletely within the nucleus. Are round with smooth margins, are sharply demarcated. They are outlined by a rim of dark chromatin.

INCIs should be large enough to differantiate it from bubble. INCIs tend to cluster in groups of cells

INCIs can be small and multiple in a nucleus.

Artefacts, such as bubbles, overlying red blood cells can mimic INCIs.If every cell has INCIs, it is an artefact.

Erythrocytes can be misleading. INCIs must be completely within the nucleus Extension from nuclus is a hint for differentiation.

BFN/NEOPLASM

Nucleoli are inconspicuous to invisible.

Nucleoli can be prominent in benign,

hyperplastic, repair (single)

Multiple nuceloli suggest malignancy

Marginated nucleoli suggest PTC .

Prominent , central nucleoli suggest follicular neoplasia.

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Cell type• Variable cell types /uniform cells

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

BFN/NEOPLASM

Dense/ picnotic/ vesicular/open. Powdery fine, PTC

Salt and pepper chromatin, Medullary thyroid Ca

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Cell type• Variable cell types /uniform cells

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

BFN/NEOPLASM

Cell borders are not prominent. Dense cytoplasm with well definedcell borders , PTC

Squamoid (dense ,waxy) cytoplasm

Hürthle cells

Medullary Ca, cytoplasmic granules

Neurosecretory granules

– Are seen as a fine red (metachromatic) cytoplasmic granules (Romanowsky )

– Are highly characteristic of medullary carcinoma but not pathognomonic and not required for diagnosis

– Can also occur rarely in other thyroid tumors

• Follicular neoplasm neoplazi

• Anaplastic Ca

• Parathyroid tumors

• Paragangliomas

Thyroid Cytopathology Evaluation Steps

• Is there Colloid ?• Scant /abundant

• How is the quality of colloid?• Watery/dense

• Cellularity• Low / high

• Arrangement• Well ordered/disorganisation of follicules/papillary structure/microfollicles /swirl

• Cell type• Variable cell types /uniform cells

• Nuclear features• Oval/spindle/irregular nuclear contour/nükleol/INCI/grooves

• Chromatin• - Pycnotic/pale,powdery/salt and pepper

• Cytoplasm• Location of the nucleus/ skuamoid/granules/ nuclear/cytoplasmic ratios

• Other background changes• Lymphocytes/giant cell/histiocytes/amyloid

BACKGROUND FEATURES

• Amyloid;

– Resembles dense colloid

– The texture ranges from hyaline to cloudy to fibrillary

– Stains metchromatically (Romanowsky ) but does not always.

– Special stains are used to confirm the presence of amyloid (Congo red).

BACKGROUND FEATURES

• Psammoma bodies

– Are concentrically laminated, calcified structures

– Are highly characteristic of PTC but not pathognomonic

• Colloid, dystrophic calcification and oxalate crystals can mimic psammoma bodies

Concentrically laminations are needed for psammoma diagnosis.

Clear and colorless in Romonowsky stains, rose to dark purple in PAP

They can be fragmented. These fragments are not adequate for definite diagnosis.

PSAMMOMA BODIES

• Occur rarely in other malignancies and very rarely in benign thyroid conditions

– Medullary Ca

– Mucoepidermoid Ca, metastasis

– Hashimoto thyroiditis

– Graves

– MNG

BACKGROUND FEATURES

• Lymphocytes

– Normal thyrocyte nucleus is about the size of lyphocytes. Bare follicular nuclei are easily mistaken for lymphocytes !

– Auotoimmune thyroiditis

– PTC (Warthin like)

Thyrocyte Lymphocyte

Lymphocytes can be crushed easily. Crushedartefact is a sign of lymphoid cells.

Hashimoto thyroiditisLymphoplasmacytic infiltrate with follicular germinal center formation

Florid lymphoid phaseThe cytology resembles an aspirate of reactive lymph nodeMajor differantial diagnosis is malignant lymphoma

BACKGROUND FEATURES

• Multinucleated giant cells

– Giant cells with foamy vacuolated cytoplasm occur in goiter, Hashimoto thyroiditis occasionally in neoplasms

– Epitheloid giant cell histiocytes characteristic of granulomatous conditions

– Epitheloid giant cell histiocytes with dense epitheloid cytoplasm are common in papillary carcinoma

Granulomatous Thyroiditis, De Quervain (subacute) Thyroiditis:Giant cells engulfing colloid with 50 to more than 200 nuclei can be either foreign body type or Langhan typeAcute and chronic inflamation, dense, scant colloid

Granulomas and scant dense colloid

Follicular epithelium tends to be sparse but reactive .Hurthle cells and numerous follicular center lymphocytes which are typical for Hashimato thyroid can not be seen

Thyroid FNA Summary• FNA of thyroid nodule is benign until proven

otherwise.

• Most thyroid nodules are benign – Most of benign nodules are colloid nodules

– Most colloid nodules can be diagnosed by cytology.

• Most malignant nodules are PTC. – Most PTCs can be diagnosed by FNA.

• Most other thyroid cancers can be diagnosed by FNA.

• Most other nonneoplastic conditions can be diagnosed FNA (Hashimoto).

• FNA is useful in the diagnosis for most of the thyroid lesions.

– It is safe for benign lesions.

– It is succesful for the PTC diagnosis which is the commonest thyroid malignancy.

Thyroid FNA SummaryMost diagnostic problems are related to highly

cellular follicular lesions.

– Most cellular follicular lesions are benign.

• Follicular carcinomas cannot be diagnosed or excluded with certainly by FNA.

• Hurthle cell lesions can not be diagnosed by FNA.

• Most aggresive follicular carcinomas can at least be suspected by FNA.

Thyroid FNA Summary

• FNA is a useful screening test for nodules with high malignancy suspicion.

• The main aim is to identify all potential follicular carcinomas.

Features Suggest Follicular Carcinoma

• MARKED ARCHİTECTURAL ABNORMALİTİES

• Crowded, 3d groups

• İrregular microfollicles

• İncreased single cells

• 2) MARKED CYTOLOGIC ATYPIA

• Nuclear enlargement

• Pleomorphism

• Abnormal chromatin

• Prominent or multiple nucleoli

• Atypical mitotic figures

• Necrosis

Hurthle Cell Nodule

• A thyroid lesion exclusively Hurthle cells on FNA has about 75% chance of being neoplastic.

• If neoplastic there is 33% chance of being malignant

• Overall risk of malignancy is 25%

• Therefore, a cytodiagnosis of “suspicious for Hurthle cell neoplasm” is appropriate which requires surgery.

• Inflamation can reduce but does not eliminate the risk of malignancy

Follicular lesions

• Both the cytologic and histologic diagnosis suffer from problems with reproducibility and this affect cytologic and histologic correlation.

3 KEY FEATURES OF PTC

1) PAPİLLARY FORMATİONS;

• true papillae

• caps

2)IRREGULAR MEMBRANES;

• grooves (most cells, most fıelds)

• INCIs (even one good one)

3)SQUAMOID CYTOPLASM (some cells)

When all three features are present PTC can be diagnosed with confidence.

PTCs lacking classical nuclear features are difficult to imposibble to diagnose.

CLUES FOR PTC

• 3-dimensional tissue fragments

• Nuclear grooves and INCIs

• Powdery chromatin

• Conspicuous micronucleoli

• Squamoid cytoplasm

• Psammoma bodies

Findings requiring surgery in FNA

• HARD FINDINGS (Surgery usually indicated)

– INCIs

– Psammoma bodies

– True papillae

– Atypical mitoses

• SOFT FINDINGS (Evaluate in clinical context)

– Hurthle cells without lymphocytes

– Hypercellular with microfollicules

– Nuclear grooves

– Mitoses

THANKS

ilkserakpolat@yahoo.com