IMMUNOHISTOCHEMISTRY FOR SOFT TISSUE TUMORS

IMMUNOHISTOCHEMISTRY FOR SOFT TISSUE TUMORS Jason L Hornick, MD, PhD Director of Surgical Pathology Director of Immunohistochemistry Brigham and Women...
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IMMUNOHISTOCHEMISTRY FOR SOFT TISSUE TUMORS Jason L Hornick, MD, PhD Director of Surgical Pathology Director of Immunohistochemistry Brigham and Women’s Hospital Associate Professor of Pathology Harvard Medical School Boston, MA, USA

Immunohistochemistry: Central Role in Soft Tissue Tumor Diagnosis • Until recently, IHC was primarily used to demonstrate line of differentiation • However, most available markers show relatively limited specificity • Few available lineage-specific transcription factors

Conventional Immunohistochemistry Line of differentiation

IHC markers

Myofibroblastic

Smooth muscle actin

Smooth muscle

Smooth muscle actin, desmin

Skeletal muscle

Muscle-specific actin, desmin

Vascular

CD31, CD34

Nerve sheath (Schwann cell)

S100

Cartilage

S100

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Lineage-Restricted Transcription Factors Line of differentiation

IHC markers

Skeletal muscle

Myogenin, MYOD1

Endothelium

FLI1, ERG

Neuroectoderm

SOX10

Notochord

Brachyury

Osteoblast

SATB2

Skeletal Muscle Transcription Factors • Myogenin (MYF4) – Excellent marker for rhabdomyosarcoma – Extent of staining correlates with subtype

• MyoD1 (MYF3) – Older antibodies difficult to optimize – Often showed cytoplasmic background staining – New antibodies improved characteristics

Embryonal RMS

Alveolar RMS

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Embryonal RMS

Alveolar RMS

MYOG

Spindle Cell Rhabdomyosarcoma

MYOD1

MPNST with Heterologous RMS

MYOG

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Endothelial Transcription Factor: FLI1 • Ets family transcription factor • Most common fusion partner in Ewing sarcoma t(11;22) • Expressed in endothelial cells and most vascular tumors • Also positive in some lymphocytes, lymphoblastic lymphoma, subset of many other tumor types

Endothelial Transcription Factor: ERG • Ets family transcription factor • Expressed in normal endothelial cells • Expressed in benign vascular tumors and almost all angiosarcomas and epithelioid hemangioendotheliomas • Also positive in 50% of prostatic adenocarcinomas and 5-10% of Ewing sarcomas (with ERG rearrangements)

Spindle Cell Angiosarcoma

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Spindle Cell Angiosarcoma

ERG

Epithelioid Angiosarcoma

ERG

Spindle Cell Melanoma

ERG

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Neuroectodermal Transcription Factor: SOX10 • Member of the SOX (SRY-related HMG-box) family of transcription factors • Involved in the regulation of embryonic development and determination of cell fate • Important for neural crest and peripheral nervous system development • Relatively specific for neuroectodermal neoplasms: malignant peripheral nerve sheath tumor, clear cell sarcoma, melanoma (including desmoplastic and spindle cell melanoma)

Neurofibroma

SOX10

Schwannoma

SOX10

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MPNST

SOX10

Desmoplastic Melanoma

SOX10

Osteoblastic Transcription Factor: SATB2 • Special AT-Rich Sequence-Binding Protein 2 • Nuclear matrix protein plays a critical role in osteoblast lineage commitment • SatB2 knockout mice display impaired osteoblast differentiation with cranioskeletal defects • Deletion of SATB2 underlies craniofacial malformations and disorders of bone development in the rare human 2q33.1 deletion syndrome

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Dobreva et al. Cell 2006

Osteoblastic Transcription Factor: SATB2 • SATB2 is a sensitive and specific marker of osteoblastic differentiation in bone and soft tissue tumors • Potential utility as diagnostic adjunct in some settings: 1. When histologic features of matrix are equivocal (i.e., osteoid vs hyalinized collagen) 2. When biopsy only samples tumor with undifferentiated appearance

Osteoblastic Osteosarcoma

SATB2

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Metastatic Osteosarcoma

SATB2

Extraskeletal Osteosarcoma

SATB2

Sclerosing Epithelioid Fibrosarcoma

SATB2

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“Next Generation” Immunohistochemistry • Protein correlates of molecular genetic alterations (amplifications, deletions, mutations) • Protein products of gene fusions • Markers identified by gene expression profiling With thanks to Allen Gown

Protein Correlates of Molecular Genetic Alterations in Soft Tissue Tumors

β-catenin MDM2/CDK4 SMARCB1 (INI1) H3K27me3 SDHB/SDHA

β-catenin • CTNNB1 gene • Wnt signaling pathway (with APC) • Mutations in >90% of sporadic desmoid tumors (inherited APC mutation with LOH in patients with FAP) • IHC: aberrant nuclear staining (normal = cell membrane) • Confirm diagnosis of desmoid fibromatosis (small biopsies; recurrence vs scar)

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β-catenin • Moderate sensitivity and specificity for desmoid fibromatosis: – Nuclear staining in 70-90% desmoid tumors – Negative in GIST, smooth muscle tumors – Nuclear staining in subset of other fibroblastic/ myofibroblastic tumors: » Low-grade myofibroblastic sarcoma (30%) » Solitary fibrous tumor (40%)

• Must be interpreted in context of morphology • Negative staining does not preclude diagnosis

Desmoid Fibromatosis

Desmoid Fibromatosis

β-catenin

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Mesenteric Desmoid Fibromatosis

β-catenin

MDM2 and CDK4 • MDM2 and CDK4 on chromosome 12q13~15; role in cell cycle regulation • Amplified in nearly all cases of welldifferentiated and dedifferentiated liposarcomas (MDM2 ~98%; CDK4 ~92%) • Ring and giant marker chromosomes

Courtesy of Paola Dal Cin

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Courtesy of Paola Dal Cin

IHC for MDM2/CDK4 • Highly sensitive for DDLPS, but not entirely specific • FISH more specific • In proper context, can be very helpful in differential diagnosis: –DDLPS vs other pleomorphic/spindle cell sarcomas –Especially in small biopsy or when welldifferentiated component is absent)

Immunohistochemistry MDM2

CDK4

Dedifferentiated liposarcoma

Tumor type

98%

92%

Malignant peripheral nerve sheath tumor

65%

10%

Myxofibrosarcoma

40%

15%

Leiomyosarcoma

5%

1%

Gastrointestinal stromal tumor

0%

0%

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Well-differentiated Adipocytic Liposarcoma

MDM2

Well-differentiated Inflammatory Liposarcoma

MDM2

Dedifferentiated Liposarcoma

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Dedifferentiated Liposarcoma

MDM2

Dedifferentiated Liposarcoma

CDK4

SMARCB1 • Also known as INI1 and SNF5 • Located on chromosome 22q11 • Member of SWI/SNF multi-subunit chromatin remodeling complex • Mobilizes nucleosomes and exposes DNA to transcription factors

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SMARCB1 in Malignant Rhabdoid Tumor • Ubiquitously expressed in normal cells • Tumor suppressor gene • Biallelic inactivation (mutation/deletion) in malignant rhabdoid tumors of infancy (renal, soft tissue, atypical teratoid/rhabdoid tumor of CNS) • Loss of SMARCB1/INI1 protein expression by IHC useful to confirm diagnosis of MRT

Malignant Rhabdoid Tumor

SMARCB1/INI1

Esophageal Adenocarcinoma

SMARCB1/INI1

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SMARCB1 and Epithelioid Sarcoma • Most tumors show homozygous deletion of SMARCB1 locus • Mutations rarely detected • IHC: SMARCB1/INI1 expression lost in ~95% of epithelioid sarcomas • Helpful in differential diagnosis (especially CD34-negative cases) • Metastatic carcinomas and epithelioid vascular tumors (angiosarcoma, EHE) retain SMARCB1 expression

Hornick et al. Am J Surg Pathol 2009

Epithelioid Sarcoma

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Epithelioid Sarcoma

Epithelioid Sarcoma

SMARCB1/INI1

Epithelioid Sarcoma

SMARCB1/INI1

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Proximal-type Epithelioid Sarcoma

Proximal-type Epithelioid Sarcoma

SMARCB1/INI1

SMARCB1 Loss in Other Tumor Types • Not specific for malignant rhabdoid tumor and epithelioid sarcoma

• Renal medullary carcinoma (~100%) • Epithelioid MPNST (67%) • Soft tissue myoepithelial carcinoma (20%)

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Epithelioid MPNST

Epithelioid MPNST

S100

Epithelioid MPNST

SMARCB1/INI1

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Renal Medullary Carcinoma

SMARCB1/INI1

Malignant Peripheral Nerve Sheath Tumor • Arise in patients with NF1, sporadically, or following radiation therapy • Challenging diagnosis • Diagnostic criteria: 1. Origin from a nerve or a neurofibroma 2. Spindle cell sarcoma in a patient with NF1 3. Evidence of Schwann cell differentiation by IHC or EM » S100 protein and SOX10 only 30-50% sensitivity

• Diagnosis in sporadic setting relies on distinctive histology and exclusion of mimics

Polycomb Repressive Complex

Epigenetic modification of chromatin: • PRC2 recruits to chromatin and trimethylates histone H3 at lysine 27 • PRC1 consolidates transcriptional repression Physiologic regulation of cell fate and proper stem cell differentiation Deregulation  cancer development Modified from Sauvageau et al. Cell Stem Cell 2010

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Oct 2014

Nov 2014

Nov 2014

PRC2 and MPNST • PRC2 alterations (SUZ12 or EED mutations) in 85-90% of MPNST • Homozygous mutations result in loss of H3K27me3 (histone H3 lysine 27 trimethylation) in ~65% of MPNST • Rate of H3K27me3 loss depends on grade • IHC for H3K27me3 highly specific diagnostic marker Schaefer et al. Mod Pathol 2016 Prieto-Granada et al. Am J Surg Pathol 2016

Immunohistochemistry for H3K27me3 in Malignant Peripheral Nerve Sheath Tumors Tumor type MPNST (total)

H3K27me3 complete loss

H3K27me3 partial loss

H3K27me3 loss (total)

61%

7%

68%

Low grade

30%

10%

Intermediate grade

60%

7%

High grade

90%

3%

40% 67% 93%

Sporadic

57%

5%

62%

NF1-associated

51%

16%

67%

Radiation-associated

95%

0%

95%

Epithelioid

0%

0%

0%

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IHC for H3K27me3 in Other Neoplasms Tumor type

H3K27me3 loss

Cellular schwannoma

0%

Atypical neurofibroma

0%

Monophasic synovial sarcoma

0%

Leiomyosarcoma

0%

Dedifferentiated liposarcoma

0%

Myxofibrosarcoma

0%

Malignant solitary fibrous tumor

0%

Low-grade fibromyxoid sarcoma

0%

Spindle cell rhabdomyosarcoma

0%

Gastrointestinal stromal tumor

0%

Fibrosarcomatous DFSP

0%

Spindle cell melanoma

0%

Radiation-associated sarcoma NOS

20%

Malignant Peripheral Nerve Sheath Tumor

H3K27me3

Malignant Peripheral Nerve Sheath Tumor

H3K27me3

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Malignant Peripheral Nerve Sheath Tumor

H3K27me3

Cellular Schwannoma

H3K27me3

Monophasic Synovial Sarcoma

H3K27me3

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Leiomyosarcoma

H3K27me3

Melanoma

H3K27me3

Succinate Dehydrogenase Mutations and Tumorigenesis • Familial paraganglioma syndrome – Germline mutations in SDH subunit genes (complex II of electron transport chain/Kreb cycle) – Most common inherited paraganglioma syndrome

• Carney-Stratakis syndrome (paraganglioma + gastric GIST) – Also caused by germline mutations in SDH subunit genes

• Carney triad (paraganglioma + gastric GIST + pulmonary chondroma) – Usually caused by SDHC promoter hypermethylation

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Succinate Dehydrogenase Deficiency • Mutations in SDH subunit genes (or promoter methylation) lead to loss of protein expression • IHC for SDHB: loss of normal staining pattern (irrespective of which gene is mutated) • IHC for SDHB can identify SDH-mutant paragangliomas and GISTs • Similar findings observed in Carney triadassociated, pediatric, and similar adult “wildtype” gastric GISTs (without KIT/PDGFRA mut) • IHC for SDHB is a good screening tool for identifying this clinically distinctive class of gastric GISTs: “SDH-deficient GISTs”

SDH-deficient GISTs • • • • • •

Only arise in the stomach Multinodular/plexiform growth pattern Epithelioid >> mixed morphology Not that rare (~8% of gastric GISTs) Lymph node metastases common Distant metastases common – clinically indolent • Current risk assessment criteria do not predict behavior for this class • No response to imatinib

Frequency of SDH-deficient GISTs

Miettinen et al. Am J Surg Pathol. 2011

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SDH-deficient GIST

SDH-deficient GIST

Stomach

KIT-mutant GIST

58-year-old male

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SDH-deficient GIST

11-year-old female

SDH-deficient GIST

42-year-old female

SDH-deficient GIST

34-year-old female

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SDH-deficient GIST

49-year-old female

SDH-deficient GIST

Metastatic SDH-deficient GIST

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SDH-deficient GISTs: Immunohistochemistry • Similar phenotype as conventional GIST (KIT, DOG1, CD34+) • IHC for SDHB: loss of normal granular cytoplasmic (mitochondrial) staining • IHC for SDHB excellent tool for confirming diagnosis of this clinically distinctive class of gastric GISTs

KIT

KIT

DOG1

CD34

desmin

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IHC for SDHB and Genotype

Doyle et al. Histopathology. 2012

KIT exon 11-mutant GIST

SDHB

SDH-deficient GIST

SDHB

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SDH-deficient GIST

SDHB

SDH-deficient GIST

SDHB

Multinodular architecture in GIST is highly associated with SDH deficiency

Sensitivity

99%

Specificity

99%

Doyle et al. Histopathology. 2012, with updated data

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What about SDHx Mutations in GIST? • Unlike SDH-deficient paragangliomas, only a small subset of SDH-deficient GISTs (25%) harbor mutations in SDHB, SDHC, or SDHD • Mutations in ANY SDH subunit gene lead to loss of expression of SDHB • Recent studies identified common SDHA mutations in SDH-deficient GISTs (35-40%) • Lead to loss of expression of BOTH SDHB and SDHA

SDHA-mutant GIST

SDHA-mutant GIST

KIT

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SDHA-mutant GIST

SDHA

Wagner et al. Mod Pathol. 2013

SDHAmutant GIST

SDHB

SDHA

SDHB

SDHA

SDHBmutant GIST

What about SDH-Deficient GISTs that lack SDHx Mutations? • Nearly all show SDHC promoter-specific CpG island hypermethylation (“epimutation”) and gene silencing • Most GISTs in Carney triad have SDHC epimutation • Leads to loss of expression of SDHB by IHC (similar to tumors with mutations) Killian et al. Sci Transl Med. 2014

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SDH-deficient GIST

Feature

SDH-deficient GISTs

GISTs with intact SDH

Age predilection

Children and young adults

Older adults

Gender distribution

F >> M

F=M

Anatomic site

Stomach

Entire GI tract

Multifocality

Common

Rare

Multinodular architecture

Always

Rare

Cytomorphology

Epithelioid or mixed

Spindle cell >> epithelioid

Prognosis predicted by site, size, and mitotic rate

No

Yes

Lymph node metastasis

Common

Exceptional

Clinical course of metastases

Indolent

Aggressive

Sensitive to Imatinib

No

Most cases

KIT/PDGFRA mutations

None

~95%

SDHx mutations (germline)

~50%

None

Carney-Stratakis syndrome (SDHx mutations)

Neurofibromatosis 1

Syndromic associations

Carney Triad (SDHC promoter hypermethylation)

Familial GIST (germline KIT or PDGFRA mutations)

Protein Products of Gene Fusions WT1 TFE3 ALK and ROS1 STAT6 CCNB3 CAMTA1

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TFE3 • Alveolar soft part sarcoma: – Translocation: t(X;17)

– Fusion gene: – Protein:

ASPSCR1-TFE3 TFE3 (nuclear)

• Xp11 translocation RCC • Small subset of PEComas • Subset of “malignant” epithelioid hemangioendotheliomas Antonescu et al. Genes Chromosomes Cancer 2013

Alveolar Soft Part Sarcoma

Alveolar Soft Part Sarcoma

TFE3

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Epithelioid Hemangioendothelioma with TFE3 rearrangement

Epithelioid Hemangioendothelioma with TFE3 rearrangement

CD31

Epithelioid Hemangioendothelioma with TFE3 rearrangement

TFE3

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ALK • Inflammatory myofibroblastic tumor: – Translocation in 50% of cases – Fusion gene:

ALK-various partners

– Protein:

ALK (usually cytoplasmic)

• Also positive in 50% of anaplastic large cell lymphomas, 5% of lung adenocarcinomas, subset of neuroblastomas, alveolar rhabdomyosarcomas, MPNSTs

Fusion Partners and ALK Staining Pattern Chromosomal location

Tumor type

ALK staining pattern

5q35

ALCL

Cytoplasmic/nuclear/nucleolar

TPM3 (tropomyosin 3)

1q21

IMT and ALCL

Diffuse cytoplasmic

TPM4 (tropomyosin 4)

19p13

IMT

Diffuse cytoplasmic

2q35

IMT and ALCL

Diffuse cytoplasmic

11p15

IMT

Diffuse cytoplasmic

SEC31L1

4q21

IMT

Diffuse cytoplasmic

TFG (TRCK fusion gene)

3q21

ALCL

Diffuse cytoplasmic

CLTC (clathrin heavy chain)

17q23

IMT and ALCL

2q11

IMT

Nuclear membrane

Xq11

ALCL

Plasma membrane

2p22

Adenocarcinoma of lung and IMT

Diffuse cytoplasmic

Gene fusion partner NPM (nucleophosmin)

ATIC (AICAR transformylase/ IMP cyclohydrolase)

CARS (cysteinyl-tRNA synthetase)

RANBP2 (Ran-binding protein 2) MSN (moesin; membraneorganizing extension spike protein)

EML4 (echinoderm microtubuleassociated protein like-4)

Granular/punctate cytoplasmic

Anaplastic Large Cell Lymphoma NPM-ALK

ALK

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Lung Adenocarcinoma EML4-ALK

ALK

Inflammatory Myofibroblastic Tumor

Inflammatory Myofibroblastic Tumor

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Inflammatory Myofibroblastic Tumor TPM3-ALK

ALK

Epithelioid Inflammatory Myofibroblastic Sarcoma

Epithelioid Inflammatory Myofibroblastic Sarcoma RANBP2-ALK

ALK

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Targeted Therapy • Small molecule inhibitors of ALK kinase recently developed

• Clinical benefit for patients with advanced EML4-ALK+ lung adenocarcinomas • Efficacy in ALK+ IMT promising • Clinical trials ongoing

Multifocal Recurrent IMT Treated with ALK Inhibitor Crizotinib

3 months

Butrynski et al. N Engl J Med 2010

ALK-Negative Inflammatory Myofibroblastic Tumors? • Molecular pathogenesis largely unknown • Recent study identified rearrangements of ROS1 (encodes related receptor tyrosine kinase), RET, and PDGFRB in subset of ALK-negative IMTs Lovly et al. Cancer Discov 2014 Antonescu et al. Am J Surg Pathol 2015

• IHC for ROS1 correlates with ROS1 rearrangement in lung adenocarcinoma

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Lung Adenocarcinoma CD74-ROS1

ALK ROS1

Courtesy of Paola Dal Cin

Inflammatory Myofibroblastic Tumor TFG-ROS1

ROS1

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Inflammatory Myofibroblastic Tumor ALK-CLTC

ROS1

Solitary Fibrous Tumor • Anatomically ubiquitous fibroblastic neoplasm (pleura, retroperitoneum, abdomen, head & neck)

• “Patternless” architecture, varying cellularity, prominent stromal collagen, dilated branching (“staghorn”) vessels • “Hemangiopericytoma” synonymous with SFT (uniform hypercellularity) • CD34 positive in 95% of cases, but not specific (many other tumor types positive)

Solitary Fibrous Tumor

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Solitary Fibrous Tumor

Hemangiopericytoma = Solitary Fibrous Tumor

Cellular Solitary Fibrous Tumor

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Malignant Solitary Fibrous Tumor

5% of SFTs are CD34 negative

CD34

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Solitary Fibrous Tumor and STAT6 • NAB2-STAT6 consistent fusion gene • Both genes on chromosome 12q13 in close proximity (overlapping) • Too close together for conventional FISH approaches • Recent studies showed that nuclear STAT6 expression specific for SFT

Doyle et al. Mod Pathol 2014

Solitary Fibrous Tumor

STAT6

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Solitary Fibrous Tumor

STAT6

Malignant Solitary Fibrous Tumor

STAT6

Doyle et al. Mod Pathol 2014

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Dedifferentiated Liposarcoma

STAT6

Doyle et al. Mod Pathol 2014

Monophasic Synovial Sarcoma

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Monophasic Synovial Sarcoma

STAT6

Ewing-like Sarcoma with BCOR-CCNB3

• • • • • •

Children, adolescents, young adults Male predominance Bone >> soft tissue Variably round or spindle cell morphology Paracentric inversion on X chromosome Gene fusion leads to high-level nuclear expression of CCNB3

BCOR-CCNB3 sarcoma

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BCOR-CCNB3 sarcoma

BCOR-CCNB3 sarcoma

CCNB3

Epithelioid Hemangioendothelioma • Originally considered ‘intermediate’ biologic potential • Now recognized fully malignant, albeit less aggressive than angiosarcoma • Most common sites: soft tissue, lung, liver, bone • Presentation and prognosis depend on anatomic site • Soft tissue – usually solitary • Bone, visceral sites – often multifocal

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Epithelioid Hemangioendothelioma

Epithelioid Hemangioendothelioma

Epithelioid Hemangioendothelioma

CD31

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“Malignant” Epithelioid Hemangioendothelioma

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Tanas et al. Sci Transl Med 2011

Immunohistochemistry for CAMTA1 • Nuclear staining in most cases of EHE • Negative in epithelioid hemangioma and epithelioid angiosarcoma • Negative in nearly all carcinomas • Negative in other epithelioid mesenchymal tumors • Useful diagnostic marker for EHE Shibuya et al. Histopathology 2015 Doyle et al. Am J Surg Pathol 2016

Doyle et al. Am J Surg Pathol 2016

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Epithelioid Hemangioendothelioma

CAMTA1

Epithelioid Hemangioendothelioma

CAMTA1

Epithelioid Hemangioendothelioma

liver

CAMTA1

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Epithelioid Hemangioendothelioma

lung

CAMTA1

Epithelioid Hemangioma

CAMTA1

Epithelioid Angiosarcoma

CAMTA1

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Immunohistochemistry for CAMTA1 • CAMTA1 positive in 44 of 48 (92%) conventional EHE • CAMTA1 positive in 7 of 11 (64%) “malignant” EHE • Of 8 CAMTA1-negative tumors, 6 were positive for TFE3 • Overall 97% of EHE cases positive for either CAMTA1 or TFE3 Doyle et al. Am J Surg Pathol 2016

Epithelioid Hemangioendothelioma

CAMTA1

TFE3

Diagnostic Markers Identified by Gene Expression Profiling • DOG1 (ANO1) – Gastrointestinal stromal tumor

• TLE1 – Synovial sarcoma

• NKX2-2 – Ewing sarcoma

• MUC4 – Low-grade fibromyxoid sarcoma – Sclerosing epithelioid fibrosarcoma

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Newer GIST Marker: DOG1 • • • • • •

“Discovered on GIST 1” Also known as ANO1 (anoctamin 1) Calcium-activated chloride channel Expressed in interstitial cells of Cajal Fundamental role in slow wave generation Highly sensitive and specific for GIST Uterine-type retroperitoneal leiomyoma (~10%) Synovial sarcoma (~15%)

• Positive in ~50% of KIT-negative GIST • Monoclonal antibody = K9

KIT-negative GIST

PDGFRA mutation

DOG1, a diagnostic marker for GIST

Discovered on GIST1

Courtesy of Matt van de Rijn

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KIT

DOG1

DOG1

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PDGFRA mutation

KIT

PDGFRA mutation

DOG1

Courtesy of Matt van de Rijn

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TLE1 • Transducin-like enhancer of split1 • Transcriptional corepressor inhibits Wnt signaling • Repression of differentiation • Gene expression profiling: TLE1 excellent discriminator of synovial sarcoma from other sarcoma types

TLE1 • IHC: strong, diffuse nuclear TLE1 sensitive and relatively specific for synovial sarcoma

• Can be helpful in differential diagnosis: – Positive in 80-90% of synovial sarcoma

– Positive in 10-20% MPNST (usually weak) – Positive in 5-10% of SFT (usually weak) – Negative in Ewing sarcoma

Monophasic Synovial Sarcoma

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Poorly Differentiated Synovial Sarcoma

Biphasic Synovial Sarcoma

TLE1

Monophasic Synovial Sarcoma

TLE1

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Poorly Differentiated Synovial Sarcoma

TLE1

Malignant Peripheral Nerve Sheath Tumor

TLE1

NKX2-2 • Homeobox transcription factor involved in neuronal development and glial/ neuroendocrine differentiation • Gene expression profiling: NKX2-2 downstream target of EWSR1-FLI1 fusion • NKX2-2 required for oncogenic transformation

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NKX2-2 • IHC: diffuse nuclear NKX2-2 sensitive marker for Ewing sarcoma (90-95%) • Also positive in Ewing sarcoma with EWSR1-ERG and “atypical” Ewing sarcoma • Imperfect specificity: mesenchymal chondrosarcomas often positive (also olfactory neuroblastomas)

Hung et al. Mod Pathol 2016

Ewing Sarcoma

NKX2-2

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Ewing Sarcoma EWSR1-FLI1

NKX2-2

Ewing Sarcoma EWSR1-ERG

NKX2-2

“Atypical” Ewing Sarcoma

NKX2-2

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CIC-DUX4 Sarcoma

NKX2-2

BCOR-CCNB3 Sarcoma

NKX2-2

Mesenchymal Chondrosarcoma

NKX2-2

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MUC4 • High-molecular-weight transmembrane glycoprotein • Expressed in colonic epithelium, among others • Gene expression profiling: MUC4 excellent discriminator of low-grade fibromyxoid sarcoma from histologic mimics

MUC4 in Low-Grade Fibromyxoid Sarcoma • IHC: MUC4 highly sensitive and specific marker for low-grade fibromyxoid sarcoma • Can be helpful in differential diagnosis: –Positive in almost 100% of LGFMS –Negative in soft tissue perineurioma, MPNST, myxofibrosarcoma, solitary fibrous tumor, desmoid fibromatosis, intramuscular myxoma

Low-grade Fibromyxoid Sarcoma

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Low-grade Fibromyxoid Sarcoma

Low-grade Fibromyxoid Sarcoma

Soft Giant Tissue Collagen Perineurioma Rosettes

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Soft Tissue Perineurioma

LGFMS

Low-grade Fibromyxoid Sarcoma Up to 80%

EMA

Low-grade Fibromyxoid Sarcoma

MUC4

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Low-grade Fibromyxoid Sarcoma

MUC4

Soft Tissue Perineurioma

MUC4

Intramuscular/Cellular Myxoma

MUC4

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Sclerosing Epithelioid Fibrosarcoma • Aggressive sarcoma that may mimic metastatic carcinoma • Composed of cords of epithelioid cells in densely hyalinized stroma • Until recently, no diagnostic markers • Some cases of sclerosing epithelioid fibrosarcoma are associated with LGFMS • Gene fusions overlap with LGFMS (EWSR1-CREB3L1 >> FUS-CREB3L2)

MUC4 in Sclerosing Epithelioid Fibrosarcoma • MUC4 strongly, diffusely positive in 90% of sclerosing epithelioid fibrosarcomas • MUC4 positive in nearly all hybrid tumors with both LGFMS and SEF components • Can be helpful in differential diagnosis: – Negative in nearly all other epithelioid soft tissue tumors – Positive in glandular component of biphasic synovial sarcoma

Sclerosing Epithelioid Fibrosarcoma

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Sclerosing Epithelioid Fibrosarcoma

MUC4

Sclerosing Epithelioid Fibrosarcoma

MUC4

Biphasic Synovial Sarcoma

MUC4

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Summary • Rapid evolution in understanding of genetics of soft tissue tumors • Molecular genetic findings lead to “next generation” IHC markers • Gene expression profiling provides novel markers to discriminate among classes of histologically similar tumors • Should lead to more reproducible, accurate diagnosis of rare tumor types

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