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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