What's Wrong with FNA of Thyroiddistribute.cmetoronto.ca/LMP1201/10_1000_Borner.pdf · Communication - The Thyroid Bethesda Follicular Lesion of Undetermined Significance Situations

Thyroid Cytology

Scott Boerner MD FRCPC Head, Division Cytopathology, University Health Network

Associate Professor, University of Toronto [email protected]

UNIVERSITY of TORONTO

Presentation Objectives

Review “Thyroid Bethesda” terminology.

Illustrate the cytoarchitecture of the thyroid.

Investigate the diagnostic features of papillary thyroid carcinoma.

Develop an approach to follicular patterned lesions and Hürthle cell (oncocytic) lesions.

Communication - The Thyroid Bethesda

6 tiered scheme Nondiagnostic or Unsatisfactory

Benign

Follicular lesion (Atypia) of undetermined significance

Neoplasm (or suspicious for neoplasm) • Follicular neoplasm

• Hürthle cell neoplasm

Suspicious for malignancy

Malignant


Benign Low risk of malignancy (0-3%)

Subcategories: • “Consistent with benign follicular nodule”

– Nodular goiter, colloid nodule, hyperplastic/adenomatoid nodule

• “Consistent with lymphocytic (Hashimoto) thyroiditis in proper clinical context”

• “Consistent with granulomatous (subacute) thyroiditis”

• Other

At UHN we use the terms: • “Benign thyroid tissue” and “Lymphocytic thyroiditis” and etc.

– “Follicular nodule” is too close to “follicular lesion” and “follicular neoplasm” – confuses the clinicians


Follicular Lesion of Undetermined Significance – This abbreviates as “FLUS”

» I prefer Follicular Lesion of Uncertain Finding (FLUF)

» Or Follicular Lesion of Undetermined Significance, Help! (FLUSH)

Alternative name “Atypia of Undetermined Significance (AUS)

Cytomorphology

• “Not benign” or “not neoplasm” or “not suspicious”


Follicular Lesion of Undetermined Significance

Situations in which it may be used

• I endorse this:

– Samples with technically compromised morphology

» Nuclear morphology is not discernible

» Much of the epithelium is obscured by blood or other artefact

• Of course this means, if it is your lab, you must do something to eliminate the compromising issue.




• I am not a fan of these:

– Microfollicular predominant pattern, but not enough for follicular neoplasm (i.e. in sparsely cellular FNA)

– Predominance of Hürthle cells in sparsely cellular FNA with scant colloid

– Moderate to marked cellularity, exclusively Hürthle cells, yet clinical setting suggests benign Hürthle cell nodule (Hash or multinodular goiter)

– Focal features of papillary carcinoma (grooves, enlarged nuclei, pale chromatin, altered nuclear contour/shape) in an otherwise benign appearing sample

» Especially in Hashimoto or with abundant colloid




• I am not a fan of these:

– Cyst-lining cells with grooves, prominent nucleoli, nuclear elongation and/or intranuclear inclusions (WHAT!!!) in an otherwise predominantly benign appearing sample

– Minor population of follicular cells with nuclear enlargement and prominent nucleoli

– Atypical lymphoid infiltrate, (in which repeat aspirate for flow cytometry is desirable) but not sufficient to consider suspicious for malignancy



Used in approximately 3-18% of reports

• But varies widely

• Recommendations to:

– “Try to limit its use to approximately 7% or fewer of all thyroid FNA”

– Or AUS/malignant ratio between 1.0 to 3.0

Risk of malignancy 5-15%

• Some reports 20-25%

– Variability to be expected, because of the wide variation in definitions used.


Follicular neoplasm / Hürthle cell neoplasm In my opinion, this term is trying to identify follicular-

patterned carcinomas

Things that trigger the diagnosis “follicular neoplasm” • Non-neoplastic

– Hyperplasia / goiter – we should be trying to avoid this

• Benign neoplasia – Adenomas – this is OK, they should come out, need to examine

capsule » I think many follicular adenoma are not recognizable on cytology

• Malignant neoplasia – Follicular variant of papillary carcinoma

– Follicular (Hürthle cell) carcinoma

• Risk of malignancy estimated 15-30%


Suspicious for malignancy

Suspicious for papillary carcinoma

• The bulk of cases will be suspicious for papillary ca

Suspicious for ___________

• Medullary carcinoma

• Lymphoma

• Metastasis

• Others

Risk of malignancy: 50-75%

• I would hope for 85+%


Malignant

Risk of malignancy 97-99%


Nondiagnostic or Unsatisfactory For application to:

• Limited cellularity • Poor fixation and preservation • Cyst contents

– BUT, unsatisfactory with cyst contents to be separated from the unsatisfactory due to low cellularity (but not cystic)

Ed Cibas (AJCP 2009;132:658-665 & Thyroid 2009;19:1159-1165)

• Strong advocate of epithelial quantitation – 6 groups each composed of at least 10 cells

Cytoarchitecture of Thyroid

There are 5 cytoarchitectures in thyroid

Monolayered sheets

Syncytial clusters (aggregates)

Epithelium with transgressing vessels

Microfollicular structures

Papillary structures


Monolayered sheets

Normal thyroid follicle histology

• Variably sized but large (100 to 1,000 epithelial cells)

• Single layer of epithelial cells

• Central colloid

• Separated and supported by a delicate fibrovascular stroma

FNA ruptures the follicle liberating the epithelial cells as variably sized flat sheets

• “Monolayered sheets”


Monolayered sheets = macrofollicles In many cases – but not always

• Macrofollicles are benign – Usually – but not always

Cytology • Simple sheet, composed of one cell layer

• May fold on itself, generating 2 or rarely 3 layers – Folding identified by the distinct layers found when

changing focal planes

• “Honeycomb” appearance may be seen – Cell boundaries often can be resolved

• Nuclei are well spaced with intervening cytoplasm


Monolayered sheets

Sometimes represent denuded papillae

• De-gloving injury to the papillary epithelium

Even when a monolayered sheets truly represents a macrofollicle

• Macrofollicles are occasionally present in neoplasms.


Monolayered sheets are

Usually macrofollicles Benign (usually)

Sometimes papillae Could be malignant

How do you tell?

The monolayered sheet itself is not unique

• Look at the nuclei – for features of papillary carcinoma

• Look for fibrovascular stalks


Syncytial clusters

Represent the disordered growth of the epithelium

• Increased cell layers from the normal 1 cell layer

• Increase N/C ratio in the cells

• Colloid depletion

Neoplastic Character

Neoplastic Character

But may also be seen in reactive conditions - thyroiditis


Syncytial clusters

Cytology

• Disorganized group of nuclei (haphazardly arranged)

– Inconstant distance between nuclei

– Inconstant focal planes in which nuclei are found

• Apparent loss of cell boundaries

• The apparent syncytial nature is not important

– It is the loss of ordered structure that is important


Transgressing vessels Really an extension from the syncytial clusters

Represents • “Neo-vascularization” of thick epithelial structures

• Abnormal vessels occurring in neoplasms

Cytology • Vascular structures (capillary size or larger) with loosely

adherent epithelial cells arranged around the vessels – Appears as if the vessels “transgresses” or course through

the epithelial cells

• Dissociated epithelial cells in background


Transgressing vessels

Originally described as a feature to aid in the distinction of Hürthle nodule from Hürthle neoplasm

• Transgressing vessels Hürthle neoplasm

• No transgressing vessels Hürthle cell nodule

Not restricted to Hürthle cell lesions

• But not generally noted in textbooks


Microfollicular structures Can occur normally or as a neoplastic growth

pattern • Normal macrofollicles & microfollicles

• Neoplastic predominance of microfollicles

It is not the finding of microfollicles that is important

• It is when microfollicles take over the sample!! – Must weigh the microfollicles against the monolayered

sheets


Microfollicular structures

Are not just small follicles!

Cytology

• 6 to 18 epithelial cells radially arranged around small droplet of colloid or a central clear space

I consider microfollicles significant if 30-40% of the epithelium is present in this architecture



I am a rigid pathologist and do not accept what some cytologists call a “papillary structure”

A papillary structure must have a fibrovascular core

• Actually in cytology we usually have denuded or partially denude fibrovascular cores

– True intact papillary structures are less frequent.



Occur in

• Papillary carcinoma (common entity)

• Papillary hyperplasia (rare entity)

To identify that this papilla is from a papillary carcinoma, you must find the nuclear features of papillary carcinoma in the epithelial cells

Papillary Carcinoma

Malignancy defined by a constellation of cytologic findings

Architectural

• Syncytial clusters of epithelial cells

Nuclear

• Enlarged & oval nuclei

• Powdery (fine pale) chromatin

• Nucleoli

• Nuclear grooves

• Intranuclear cytoplasmic pseudo-inclusions

Papillary Carcinoma

Malignancy defined by a constellation of cytologic findings

Architectural

• Syncytial clusters of epithelial cells

Nuclear

• Enlarged oval nuclei

• Powdery (fine pale) chromatin

• Nucleoli

• Nuclear grooves

• Intranuclear cytoplasmic pseudo-inclusions

? Specific to papillary carcinoma ?

Frequently, but not always a marker of a follicular epithelial neoplasia

Papillary Carcinoma

Nuclear enlargement

Enlargement is asymmetrical resulting in ovoid nuclei

Results in increased N/C ratio, manifest as:

• Nuclear crowding

• Nuclear overlapping

• Syncytial architecture of epithelial tissue fragments

– i.e. syncytial clusters

Papillary Carcinoma

Changes in chromatin texture

More pale with increase granularity

Prone to areas of chromatin clearing

• Appear as “holes” in the nucleus

– Must differentiate from inclusions

Susceptible to development of “Orphan Annie” or optically clear nuclei if:

• Formalin fixed

• Air-dried, rehydrated and UltraFast Pap stained

• Not evident in most cases of routinely prepared FNA

Papillary Carcinoma

Nucleoli

Usually of micronucleoli variety and not macronucleoli

Eosinophilic

Frequently multiple, but may be single

Often eccentrically place along nuclear membrane

“Bare” nucleoli found

• Clearing of chromatin around nucleolus

– Appears as if it is sitting within a hole in the nucleus

Papillary Carcinoma

Nuclear irregularities

Nuclear membranes in papillary carcinoma are variable

• Fairly smooth contoured

• Minor wavy or saw tooth nuclear membrane irregularities

• Profoundly irregular membranes (raisinoid)

Reflect deranged nuclear skeletal elements

• Also predisposes to development of

– Nuclear grooves

– Intranuclear inclusions

Papillary Carcinoma

Nuclear Grooves

Multiple names

• Lineage chromatin ridge, nuclear crease, nuclear fold, etc.

Represents linear invagination of nuclear membrane parallel to the long axis of the nucleus

• Seen as a “line” running along the axis of the nucleus

• If nuclear orientation optimal

– Forms a “notch” as the groove crosses over the nuclear horizon.

Papillary Carcinoma

Nuclear grooves Visualization is dependent on nuclear orientation

• As is true of any nuclear cleft

Nuclear grooves occasionally lead to debate • “Is it real or not?”

• The notch is very evident and not a feature open to challenge

The groove must be within an epithelial cells • Histiocytes have elongated and “groove” nuclei that may

be mistaken as abnormal epithelial cells

Papillary Carcinoma

Nuclear grooves

Are seen in air dried Romanowsky stained material

• “Finger nail scratches” across surface of nucleus

I find them more difficult to appreciate than alcohol fixed material

Papillary Carcinoma

Intranuclear inclusion

Full name:

• Cytoplasmic intranuclear pseudoinclusion

• Shortened to “intranuclear inclusion”

A profound invagination of cytoplasm into the nucleus

• Kind of an exaggerated nuclear groove

Papillary Carcinoma

Intranuclear inclusion

Cytologic criteria

• Diameter of the inclusion must be at least ¼ of the nuclear diameter

• Edges of the inclusion must be sharply defined

– As sharply defined as the remainder of the nuclear membrane

• Inclusion must be round and regular

• Inclusion must look the same as the cytoplasm

– In colour and density – it contains cytoplasm after all

• Inclusion must be found in an epithelial cell

Papillary Carcinoma

Intranuclear inclusions

The same criteria for intranuclear inclusions are applied to:

• Alcohol fixed pap stained material

– Direct smears

– ThinPrep

– Cytocentrifuge preps

• Air-dried, Romanowsky stained material

Papillary Carcinoma

Intranuclear inclusions Mimics of intranuclear inclusions:

• Air drying induced “hole” – Tend to be small

– Fuzzy edges

– Spherical (the same as a true inclusion)

– Appear empty (white)

– Any cell type

• Chromatin pallor – Variable size, often small

– Fuzzy edges

– Irregular outline, not spherical

– Appear pale (similar to a true inclusion)

– Usually epithelial cells

Papillary Carcinoma

Specificity of grooves

Nuclear grooves are not specific to papillary carcinoma

• Seen in a number of conditions, notably lymphocytic thyroiditis

Weak relationship between the number of grooves and papillary carcinoma

• More grooves – more likely to be papillary carcinoma

Be cautious with grooves alone

Papillary Carcinoma

Specificity of inclusions Much greater specificity than grooves, but not

pathognomic

May also be seen in • Medullary carcinoma

• Lymphocytic thyroiditis – I question this. How have we established it is not

carcinoma? – usual answer – an expert’s opinion.

• Hyalinizing trabecular tumour

Must not be seen in papillary hyperplasia

Papillary Carcinoma

“Unique” features of papillary carcinoma

Nuclear grooves

Nuclear inclusions

Are NOT unique or specific to, nor pathognomic of papillary carcinoma

Papillary Carcinoma

Can you have a papillary carcinoma that does not have intranuclear inclusions?

Yes – but be cautious

• Intranuclear inclusions are an excellent predictor that the surgical pathology will be called papillary carcinoma.

– It is as much a predictor of a surgical pathologist’s behavioural pattern as it is a predictor of a specific pathologic entity.

Suspicious for PTC

I usually use in the context of:

All the cytologic features of papillary carcinoma, but lacking definitive intranuclear inclusions

• Look very hard before you say there are no inclusions

• Most are follicular variant of PTC, in which intranuclear inclusions are less frequent

• Occasionally a benign mimic of PTC

The presence of psammoma bodies without epithelium or epithelium lacks the features of PTC.

Psammoma bodies

Calcified, concentrically laminated, spherical bodies Calcospherites

• “Naked” psammoma bodies

Psammoma bodies • Calcospherites surrounded by cells

May coalescence into concretions and lose their spherical structure

They are NOT the tombstone of dead cells / infarcted papillae

Psammoma bodies

Mimics of psammoma bodies

Inspissate (dense) colloid

• Lacks laminations

Amyloid


• May appear fibrillary and / or waxy

Dystrophic calcifications


• Irregular masses

Psammoma bodies

Diagnostic significance

Literature states 50% positive predictive value

• I think this is an under-estimate

A 50% PPV indicates the nodule must be examined

• Diagnosis: Suspicious for papillary carcinoma

Caveat

• Look carefully at the epithelium present

– It likely has nuclear features of papillary carcinoma

Follicular Neoplasms

Unlike papillary carcinoma, follicular neoplasms do not have “unique” nuclear features

They do have “neoplastic” nuclei

• Enlarged, somewhat ovoid nuclei

• Increased N/C ratio (syncytial clusters)

• Altered chromatin structure

• Increased prominence of nucleoli

Follicular Neoplasms

The clue to diagnosis:

Altered cytoarchitecture

• Syncytial clusters

• Transgressing vessels

• Microfollicular structures

Exclusion of nuclear features of PTC

Hürthle Cell Neoplasm

What are Hürthle cell neoplasms?

In my mind, they are the same as their “follicular” counterparts except that they show Hürthle cell differentiation

I think the most common lesion called a “Hürthle cell neoplasm” on FNA turns out to be:

• A Hürthle cell (oncocytic) variant of papillary carcinoma.

– Look hard at the nuclei of Hürthle cell neoplasms for intranuclear inclusions

Hürthle Cell

What is a Hürthle cell?

Large cell (larger than normal follicular epithelial cells)

Abundant cytoplasm

• Cyanophilic cytoplasm

• Numerous cytoplasmic granules (mitochondria)

– Eosinophilic, imparting eosinophilic tinge to cytoplasm

• Moderate to marked cytoplasmic vacuolation

• Eccentrically placed nucleus

– Enlarged, but round nucleus

– Regular, smooth nuclear membranes

– Increased chromatin chromaticity and more granular

– Prominent (single) eosinophilic nucleolus

Hürthle Cell

What is a Hürthle cell?

Normal Hürthle cells maintain a monolayered sheet architecture in FNA

• Syncytial clusters are concerning

• Transgressing vessels very disturbing

The presence of nuclear grooves is of little predictive value

The presence of intranuclear inclusions is very disturbing

Hürthle Cell Lesion?

Are Hürthle cells evil?

No - Hürthle cells can be your friend

• The combination of Hürthle cells and regular follicular cells represent a “polyclonal” population – benign

Hürthle cells are common and almost expected in most cases of thyroiditis


Are numerous Hürthle cells evil?

I do not like any cell when they seem to “gang-up” on me, but…

• A predominance of Hürthle cells is NOT a strong predictor of a Hürthle cell neoplasm

– It is something to precipitate careful examination to try to determine if the lesion is neoplastic

How do you tell if it is a Hürthle cells lesion / neoplasm?


I try at all costs to avoid “Hürthle cell lesion”, I will use Hürthle cell neoplasm

Look at the cytoarchitecture of the Hürthle cells

• Monolayered sheets Benign

• Syncytial clusters Neoplasm

• Transgressing vessels Neoplasm

Look for intranuclear inclusions

• Must exclude a papillary carcinoma, knowing it is the most common Hürthle cell neoplasm I will see

My Approach to Hürthle Cells

Nuclear Features of papillary carcinoma present

Yes

Hürthle cell variant papillary

carcinoma present

No

Complex Architectural Features*

Yes

No

Hürthle cell neoplasm

Benign thyroid tissue

* Transgressing vessels, microfollicular dominance, complex syncytial aggregates

Documents

What's Wrong with FNA of Thyroiddistribute.cmetoronto.ca/LMP1201/10_1000_Borner.pdf · Communication - The Thyroid Bethesda Follicular Lesion of Undetermined Significance Situations