linos - update ihc mesenchymal neoplasms jan 2018 · by konstantinos linos md, fcap, fasdp...

1/18/2018

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An update on immunohistochemical markers

in mesenchymal neoplasms

By Konstantinos Linos MD, FCAP, FASDPAssistant Professor of Pathology

Geisel School of Medicine at DartmouthDartmouth-Hitchcock Medical Center

Lebanon, NH, USA

• Book Royalties

Financial disclosures

A general truth!

• Some of these markers may prove to be more useful in clinical practice than others

• With time it is generally appreciated that significant overlap in staining patterns can be seen in different tumor types, some of which share similar biology or can be explained by known biologic mechanisms

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• ERG• PAX7• DUX4/ETV4• BCOR

• Claudin 4• STAT6• MUC4

Outline

ERG• Member of the ETS family of regulatory

transcription factors with diverse biological roles • Regulates endothelial cell differentiation,

angiogenesis, and expression of several endothelial-specific antigens

• Also required for embryonic stem cells to differentiate into endothelial cells

• Regulatory gene of cartilage skeletogenesis• May have crucial role in permanent cartilage

develpment

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ERG in benign vascular tumors

ERG in Hemangioendotheliomas

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ERG in angiosarcoma in comparison with CD31

ERG in non epithelial Mesenchymal, Neuroectodermal and Hematopoietic

tumors

ERG in Epithelial Neoplams

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ERG in nonvascular tumors

A hemorrhagic poorly differentiated carcinoma simulating angiosarcoma

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ERG

• From these studies ERG is positive in >95% of angiosarcomas, with a greater sensitivity compared to CD31 and CD34

• ERG usually shows a diffuse pattern of nuclear staining, which facilitates its interpretation in this context.

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Ewing Sarcoma with EWSR1-

ERG

FLI1

ERG

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Ewing sarcoma with EWSR1-FLI1

EWSR1, FLI1, ERG and their fusion proteins in Ewing Sarcoma

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Leukemia cutis cases

Reactive Leukocytic Infiltrates

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Soft Tissue Chondroma

Convetional Chondrosarcoma

ERG

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FLI1 ERG

Conclusion• ERG is therefore a useful marker for confirming

endothelial differentiation in both benign and malignant neoplasms

• Potentially useful marker to distinguish Leukemia Cutis vs reactive myeloid infiltrates

• Expression can also be seen in a subset of epithelioid sarcomas and a small percentage of Ewing sarcomas, as well as approximately 45% to 50% of prostatic carcinomas.

• ERG can be seen in selected bone and soft tissue tumor with cartilaginous differentiation

• ERG• PAX7• DUX4-ETV4• BCOR


Outline

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• Immunohistochemical detection in tumor cell nuclei of myogenin and MYOD1 currently benchmark for rhabdomyosarcoma diagnosis

• Sensitivity and specificity even in combination is imperfect

• Negative or focal myogenin in a considerable number of embryonal rhabdomyosarcomas

• MYOD1: high background and cytoplasmic staining

PAX7

• PAX7 is a paired box transcription factor required for mammalian skeletal muscle stem cells (aka satellite cells)

• It plays a critical role in mammalian myogenesis

• Controls early lineage specification, whereas MYOG and MYOD1 regulate subsequent lineage commitment

PAX7

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Embryonal Rhabdomyosarcoma

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Embryonal Rhabdomyosarcoma

Alveolar Rhabdomyosarcoma

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PAX7 and Rhabdomyosarcoma

• Potential diagnostic value of PAX7 IHC in the evaluation of rhabdomyosarcoma, especially embryonal rhabdomyosarcoma

• Less sensitive in ARMS • Could be used secondarily in desmin+,

MYOG/MYOD1 - cases

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Ewing Sarcoma

CIC-DUX4

• PAX7 a sensitive marker for Ewing Sarcoma

• Positive in NKX2-2 negative cases

• Also positive in both common and variant forms of Ewing Sarcoma

• PAX7 expression differentiates Ewing Sarcoma from CIC-DUX4 sarcoma

What accounts for the robust PAX7 expression in Ewing Sarcoma?

EWSR1-FLI fusion protein binds at position 5 to the PAX7 promoter

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Undifferentiated small round cell or spindle-cell tumor

• PAX7 positivity: Rhabdo vs Ewing Sarcoma• Positivity for desmin, MYOG, MYOD1 would

strongly favor rhabdomyosarcoma• Rare cases of ES can express myogenic features

• Diffuse membranous CD99 would favor ES• Can be positive in rhabdomyosarcomas

• NKX2.2 would support ES• WT1+, PAX7- would support CIC-DUX4

• To date IHC focused on the aberrant expression of one of the genes involved in the pathogenic translocation• WT1 in DSMRCT (EWSR1-WT1)• STAT6 in SFT (NAB2-STAT6)• FLI1 in Ewing Sarcoma (ESWR1-FLI1)• BCOR in undifferentiated sarcomas

• PAX7 in ES exploits a characteristic transcriptional read-out of the disease-causing translocation

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• ERG• PAX7• DUX4 & ETV4• BCOR


Outline

• Emerging undifferentiated sarcomas resembling but distinct from Ewing Sarcoma• t(4;19) translocation involving CIC-DUX4• t(10;19) translocation CIC-DUX4L

• Distinct transcriptional signature with poor clinical outcomes

DUX4 IHC

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CD99 WT1 FISH CIC

Ewing Sarcoma Malignant Rhabdoid Tumor

Synovial Sarcoma

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• ETV4 (ETS Variant 4)• Member of the PEA3 subgroup in the ETS

transcription factor family • Upregulation of WT1 and ETV1/4/5 in CIC-

rearranged sarcomas

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ETV4 and round cell sarcomas

• Sensitive but not entirely specific for CIC-rearranged sarcomas

• Diffuse, moderate-to-strong expression in ~90% sensitive and 95% specific



Outline

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BCOR (BCL-6 interacting corepressor)

• A subset of undifferentiated round cell sarcomas:• BCOR-CCNB3• BCOR-MAML3• ZC3H7B-BCOR• YWHAE-NUTM2B• BCOR internal tandem duplication (ITD)

• Clear cell sarcoma of the kidney• Primitive myxoid mesenchymal tumor of

infancy

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BCOR and Synovial Sarcoma

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BCOR

• BCOR IHC is highly sensitive in identifying sarcomas with BCOR abnormality• Triage for further molecular tests• Avoid extensive IHC and molecular workups in

small specimens• Synovial sarcoma should be included in the

DDx of round cell sarcomas with BCOR+

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Outline

Claudin 4 and SWI/SNF complex-deficient tumors

• Claudins are integral components of tight junctions which for barriers in epithelial, endothelial and perineurial cells

• Claudin 4 is expressed in most epithelial cells and carcinomas • Has been validated as a useful marker in the

distinction of mesothelioma (lack of expression) from metastatic adenocarcinoma (consistently +)

• It has been observed:• Epithelial component of biphasic synovial

sarcoma• Subset of Desmoplastic Small Round Cell Tumor

Claudin 4

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• Fundamental role in regulation of gene expression

• Tumor suppressor properties• SMARCB1 (INI-1)• SMARCA2 (BRM)• SMARCA4 (BRG1)• ARID1A

SWI/SNF complex

• SMARCB1 deficiency (INI1 loss)• Malignant Rhabdoid Tumor• Epithelioid Sarcoma• Subset of myoepithelial carcinomas• Epithelioid MPNST

• SMARCA4 deficiency (BRG1 loss)• Nearly all cases of ovarian small cell carcinomas

of hypercalcemic type• ARID1A deficiency

• ~half of ovarian clear cell carcinomas

SWI/SNF complex

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Epithelioid Sarcoma

Epithelioid Angiosarcoma

Epithelioid MPNST

Biphasic Synovial Sarcoma

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Ovarian Clear Cell Carcinoma

Pancreatic Rhabdoid Carcinoma

CecalRhabdoid Carcinoma

INI1-deficient SinonasalCarcinoma

Claudin 4• It may serve as a useful diagnostic adjunct in

the distinction of SWI/SNF complex deficient carcinomas from sarcomas with epithelioid morphology

• Strongly associated with true epithelial differentiation

• However absence of claudin 4 staining does not entirely exclude carcinoma

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Keratin CD34

SMARCA4

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Outline

STAT6 and Solitaty Fibrous Tumor

• STAT6 is a member of the STAT family of cytoplasmic transcription factors, which regulate gene expression by transmitting signals to the nucleus and binding to specific DNA promoter sequences

• NAB2 is a transcriptional corepressor, a regulator of the early growth response 1 (EGR1) transcription factor

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Variable truncation of the repressor domain of NAB2 with replacement by the transcriptional activation domain of STAT6

Subsequent translocation to the nucleus, where it acts as a transcriptional activator resulting in increased proliferation

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Synovial sarcoma

Cellular spindle cell lipoma

STAT6

STAT6

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Dedifferentiated liposarcoma

Pitfall!• Presence of STAT6 expression in

approximately 7% to 15% of dedifferentiated liposarcomas

• The staining pattern in dedifferentiated liposarcoma is variable and may be focal or diffuse, weak or medium to strong in intensity, unlike the generally strong diffuse pattern seen in solitary fibrous tumor

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• Unlike the predominantly nuclear pattern of staining seen in solitary fibrous tumor, both cytoplasmic and nuclear expression is common in dedifferentiated liposarcoma.

• Diffuse expression of MDM2 and CDK4 helps favor a diagnosis of dedifferentiated liposarcoma

• If doubt persists, FISH for MDM2 amplification may also be useful

FISH vs PCR

• Because STAT6 and NAB2 are located close together on the long arm of chromosome 12, FISH to demonstrate rearrangement of the genes is technically challenging and not diagnostically useful



Outline

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MUC4• MUC4 is a useful marker for low-grade

fibromyxoid sarcoma (LGFMS) and sclerosing epithelioid fibrosarcoma

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Sclerosing epithelioid sarcoma

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Monophasic synovial sarcoma and MUC4

Sclerosing epithelioid sarcoma, MUC4 and carcinoma

• Importantly, regarding SEF, in which a poorly differentiated carcinoma may fall into the differential diagnosis

• it should be remembered that MUC4 expression is seen in a variety of different carcinomas, such as pancreaticobiliarycarcinomas, breast carcinoma, and colonic adenocarcinoma.

NEVER FORGET!

• The use of all of these markers requires careful clinical correlation and knowledge of the spectrum of staining in other tumor types, as no one marker is 100% sensitive or specific for a given diagnosis

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• Email: [email protected]

• @ @ KonstantinosLin

linos - update ihc mesenchymal neoplasms jan 2018 · by konstantinos linos md, fcap, fasdp...

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