My Approach to

Diagnosis of Soft Tissue Tumors

Savannah, GA

October 2019

Cyril Fisher MA MD DSc FRCPathConsultant Pathologist,

University Hospitals Birmingham, UK

Professor Emeritus of Tumor Pathology

Institute of Cancer Research

University of London, UK

Soft Tissue Sarcomas

• Rare: sarcomas 1% of all cancers

• 50 per million: Per annum 3600

• Can arise virtually anywhere

• skin, subcutis, deep soft tissue

• organs (i.e. non soft tissue sites)

• Seen in general surgical pathology practice

• >200 subtypes

• Can mimic carcinoma, melanoma, lymphoma

Classification

• By differentiation

• (WHO consensus

2002, 2013)

• Adipocytic

• Fibroblastic/myofibroblastic

• Fibrohistiocytic

• Smooth or skeletal muscle

• Pericytic (perivascular)

• Vascular

• Chondro-osseous

• Neural

• GIST

• Uncertain differentiation

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Liposarcoma

Dedifferentiated

ALT/Well differentiated Pleomorphic

Epithelioid pleomorphic

Myxoid

Myxoid

complex karyotypet(12;16)(q13;p11) FUS-DDIT3

t(12;22)(q13;q12) EWSR1-DDIT3

t(12;16)(q13;p11) FUS-DDIT3

t(12;22)(q13;q12) EWSR1-DDIT3complex karyotype

12q13-15 amplifications

12q13-15 amplifications & others

Uncertain Differentiation

Synovial sarcoma

epithelial

Epithelioid sarcoma

epithelial (part)

Clear cell sarcoma

melanocytic

Ewing sarcoma/PNET

neuroectodermal

Desmoplastic SRCT

?mesothelial

E/S myxoid chondrosarcoma

?

Alveolar soft part sarcoma

?

PEComa

myomelanocytic

Gastrointestinal stromal tumor

?interstitial cell of Cajal

Classification

• By behavior

• (WHO consensus

2002, 2013)

• Benign

• Intermediate

• locally aggressive

• rarely metastasising

• Malignant – sarcoma

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Common Benign Soft Tissue Tumors

Common Benign ST Tumors

• Lipoma

• Myxoma

• Schwannoma

• Leiomyoma

• Hemangioma

• Nodular fasciitis

Locally aggressive

• Atypical lipomatous tumor

• Fibromatosis

• Lipofibromatosis

• Giant cell fibroblastoma

• Kaposiform HE

• Haemosiderotic fibrolipomatous tumor

Intermediate ST Tumors

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Fibromatosis

Fibromatosis

Beta catenin

Dermatofibrosarcoma

Inflammatory myofibroblastic t.

Low grade myofibrosarcoma

Solitary fibrous tumor

Myxoinflammatory fibroblastic

sarcoma

Infantile fibrosarcoma

Plexiform fibrohistiocytic tumor

Giant cell tumor of soft tissue

Intermediate ST Tumors

Hemangioendothelioma

retiform, composite,

papillary, pseudomyogenic

Kaposi sarcoma

Atypical fibroxanthoma

Angiomatoid fibrous histiocytoma

Ossifying fibromyxoid tumor

Myoepithelial tumors

Phosphaturic mesenchymal tumor

Rarely metastasizing <2%

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Sarcomas

• grade 1

• grade 2

• grade 3

Malignant ST Tumors

Soft Tissue Tumor Diagnosis

• Identify differentiation (‘lineage’)

• not from corresponding mature tissue

• cannot define cell of origin (‘histogenesis’)

• Assess malignant potential

• Clinicopathological perspective

➔ predict behavior

➔ guide treatment

➔ assess progress

Approach to Diagnosis

• Clinical features

• Gross findings

• Histology

• Ancillary techniques

• immunohistochemistry

• molecular genetics

• electron microscopy

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STT – Clinical Information

Past Medical History

• Trauma/surgery

• Previous disease

• Previous therapy

• immunosuppression

• lymphoedema

• therapeutic irradiation

Family history

• Cancer predisposition

syndromes

Mass

• Painless

• Painful

Mass effect

• Paraesthesia

• Thrombus

• Obstruction

STT – Clinical Features

• Age

• Sex

• Site

• Duration

• Size

• Depth

• Diagnostic spectrum of

malignancies is different in children

• Different tumor types occur in➔

different age groups in adults

Clinical Features - Age

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Childhood

• Neuroblastoma

• Embryonal RMS

• Acute lymphoblastic

leukaemia

• Wilms tumor

Clinical Features - Age

Adolescent

• Alveolar RMS

• Ewing sarcoma

• Desmoplastic SRCT

• Poorly differentiated

synovial sa

• Mesenchymal chondrosa

• ALL

Clinical Features - Age

Adult

• Small cell carcinoma

• Small cell melanoma

• Small cell lymphoma/leuk.

• Alveolar RMS

• Ewing sarcoma

• Round cell liposarcoma

• Poorly differentiated

synovial sa

• Endometrial stromal sa

Clinical Features - Age

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Site

Depth from surface

• Most benign tumors

occur superficially

• Site and depth relate

to prognosis

• Staging

Clinical Features

Clinical Features

Site

Depth from surface

• Most benign tumors

occur superficially

• Site and depth relate

to prognosis

• Staging

Clinical Features

Site

Depth from surface

• Most benign tumors

occur superficially

• Site and depth relate

to prognosis

• Staging

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Duration and Size

• Sarcoma ➔ longer history, larger

• Nodular fasciitis ➔ rapid growth (self-limiting)

Clinical Features

• Small specimens

• FNAC

• core needle biopsies

• open biopsies

• some resections

• Large specimens

• resections

• amputations

Types of Specimen

Core biopsies

• Embed one core per

cassette

• No levels

➔ maximal use of

available tissue

Lesions <5cm

• Embed in entirety

Small Specimens

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• Weigh, measure (mms)

• Ink margin(s)

• Fresh tissue ➔ freeze

Larger Specimens

Gross description

• Solid, cystic

• Myxoid, fibrous

• Estimate necrosis

• Dedifferentiation

Sample

• 1 block/cm

• Margins

• nearest

Larger Specimens

Intra-abdominal

mass

2019

Review Previous Pathology

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Intra-abdominal

mass

2012

Review Previous Pathology

Tissue plane

• Skin/subcutis/fascia/

muscle

Margin

• Circumscribed, infiltrative

Cellularity

• Sparse/moderate/high

Stroma

• collagenous

• hyalinised

• myxoid

• Inflammatory

Low Magnification

Some tumors resemble

corresponding normal

tissue

Morphology

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Some tumors resemble

corresponding normal

tissue

Morphology

Spindle cell

Small round cell Pleomorphic

Epithelioid

Morphology

Low power:

Patterns

• Sheets

• Nests

• Files

• Fascicles

• intersecting

• sweeping

• alternating

• storiform

• herringbone

• palisading

• Myxoid

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Fibroblasts Myofibroblasts

Smooth muscle Nerve sheath

Synovial sarcoma ‘Fibrohistiocytic’

Benign or Malignant?

• Synthesis of factors

• Pleomorphism

• Atypical mitoses

• Necrosis

• But vary according to lineage!

Symplastic LeiomyomaAtypical Schwannoma

PHAT Atypical Cutaneous FH

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• In complex karyotypic

tumors

• Not in translocation-

associated sarcomas

Pleomorphism/Atypia

LGFMS

SSES

Benign/reactive

• <5/10hpf

• (normal)

• nodular fasciitis

Malignant

• >5/10hpf

• abnormal forms

Mitoses

Per 10 hpf

• Grading criterion

Per 50 hpf

• GIST

• Ossifying fibromyxoid t.

• Glomus tumor

• Deep leiomyoma

Mitotic Index

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Immunohistochemistry

Soft Tissue Tumor Immuno Panels

Spindle

CK

CD34

SMA

Desmin

S100 pr

SOX10

MUC4

STAT6

Small round

CK

Desmin

Myogenin

CD99

FLI-1

WT1

S100 pr

NB84a

NF/NSE

CD45

Tdt

Pleomorphic

CK

SMA

Desmin

S100 pr

CDK4

p16

MDM2

Epithelioid

CK

EMA

CD34

CD31

ERG

SMA

Desmin

S100 PgR

SOX10

HMB45

Melan-A

INI1

‘Specific’ Abs According to Context

• Beta-catenin Fibromatosis

• ALK, ROS1 Inflammatory myofibroblastic tumor

• p16, MDM2 & CDK4 WD/DD liposarcoma

• INI1 Epithelioid sarcoma et al

• STAT6 Solitary fibrous tumor

• MUC4 LG fibromyxoid sarcoma

• SOX10, H3K27me3 MPNST

• CD117, DOG1 GIST

• MYC Angiosarcoma

• FOSB Epithelioid hemangioma

• RB Spindle cell lipoma

• Brachury Chordoma

• NKX2.2 Ewing sarcoma

• ETV4 CIC-DUX4 sarcoma

• CCNB3 CCNB3-BCOR sarcoma

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Immunohistochemistry

• Know purpose of each antibody

• Never rely on a single marker

No marker is 100% sensitive or specific

• Use selected panels

• Specific cellular compartment

• Negative as well as positive finding

Cytokeratin

• Widespread

• carcinoma (organ-

based)

• some sarcomas

• Focal

• synovial sarcoma

Distribution of Immunoreactivity

Beta-Catenin

Positive Negative

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CD34 and Cytokeratin

• Epithelioid sarcoma

• Epithelioid endothelial tumors

• Ectopic hamartomatous thymoma

• Superficial CD34-positive fibroblastic tumor

• SMARCA4-inactivated undiff. thoracic tumor

• Desmoplastic nested spindle cell tumor

• Hepatocellular carcinoma

• NUT midline carcinoma

Useful negatives

• INI1 many

• H3K27Me3 MPNST

• STAT6 not SFT

• TLE1 not synovial sarcoma

• MUC4 not low-grade fibromyxoid sa

Natural History of a New Diagnostic Ab

Highly specific and sensitive for one tumor type

Occasionally positive in similar tumor types

Often positive in different tumor types

Used only as part of a larger panel of Abs

No longer used

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Molecular Diagnostics

• Make or confirm a

diagnosis

• Predictive /

prognostic factors

• Targeted therapy

When to do Molecular Testing

Molecular Abnormalities in STT

• Translocations

• Non-translocational abnormalities

• Somatic mutations• activating – KIT, PDGFRA

• non-activating – SMARCB1, TSC

• Copy number abnormalities

• gene amplification – MDM2

• gene deletion – SDH, SMARCB1, SMARCA4

• Complex unbalanced karyotypes

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Translocation-associated STT

Translocation-associated Sarcomas

• >30% of sarcomas

• Balanced or unbalanced

• non-pleomorphic but mostly G3

• Non-random, leads to new fusion gene

• transcriptional regulators

• tyrosine kinases

• growth factors

Malignant Soft Tissue Tumors

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Malignant Soft Tissue Tumors

Benign Soft Tissue Tumors

Genetics and Morphology

• Different genetic abnormalities can occur in tumors of

the same lineage or morphology

• Fibrosarcoma

• Myofibroblastic tumors

• Small round cell tumors

• Liposarcoma

• The same genetic abnormalities can occur in

completely different tumor types

• EWSR1 gene rearrangements

• ASPCR1-TFE3

• ETV6-NTRK3

• YWHAE-NUT22

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Fluorescence in situ

hybridization (FISH)

• gene rearrangements

• amplification

Reverse transcription

polymerase chain reaction

(RT-PCR)

• specific fusion transcripts

• mutational analysis

Molecular Diagnostic Techniques

FISH

Gene rearrangement Gene amplification

Caveats

FISH break apart

• sensitive but not

specific

Genes can partner

with multiple others

EWSR1

FUS

USP6 etc

FISH Diagnosis

USP6 in nodular fasciitis

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STT with EWSR1 Rearrangement

• EWSR1-FLI1, EWSR1-ERG,

EWSR1-many others

• Ewing & similar sarcomas

• EWSR1-WT1

• desmoplastic SRCT

• low grade myoid tumor

• EWSR1-DDIT3

• myxoid liposarcoma

• EWSR1-NR4A3

• e/s myxoid chondrosa

• EWSR1-CREB3L1

• sclerosing epithelioid fibrosa

• EWSR1-TFCP2

• rhabdomyosarcoma

• EWSR1-CREB1, EWSR1-ATF1

• various

• EWSR1-CREM

• myxoid mesenchymal tumor

hyalinising clear cell ca

• EWSR1-POU5F1,EWSR1-PBX1,

EWSR1-PBX3, EWSR1-ZNF44,

EWSR1-KLF17

• myoepithelial tumors

• EWSR1-YY1

• mesothelioma

• EWSR1-SMAD3

• acral spindle cell tumor

Thway 2012; Flucke 2012; Panagopoulos 2013; Gru 2013; Bilodeau 2013; Ud Din 2015; Huang 2015; Antonescu 2017; Kao 2018; Chapman 2018; Watson 2018

(Ewing sarcoma RNA-binding protein 1, 22q12.2)

Caveats

RT-PCR

• specific but cannot detect

uncommon fusions

• problems with RNA

extraction

• ‘promiscuity’ of fusions

Molecular Diagnosis

‘Promiscuous’ Fusions• EWSR1-ATF1

angiomatoid FH, clear cell sarcoma, CCSLTGITmyoepithelial tumor, angiosarcoma, salivary HCCC, CCOC

• EWSR1-CREB1angiomatoid FH, clear cell sarcoma, CCSLTGIT, PPMS

• EWSR1-CREMangiomatoid FH, intracranial myxoid mesenchymal tumor, CCS

• ETV6-NTRK3infantile fibrosarcoma, inflammatory myofibroblastic tumor, mesoblastic nephroma, AML, secretory ca breast,mammary analogue secretory carcinoma of salivary glands

• ASPSCR1-TFE3alveolar soft part sa, juvenile renal cell carcinoma

• TMP3-ALKinflammatory myofibroblastic tumor, anaplastic large cell lymphoma

• YWHAE-NUTM22A/Bendometrial stromal sarcoma, clear cell sarcoma of kidney

• FUS-ERGEwing sarcoma, AML

• BRD4-NUTEwing-like sarcoma, thymic & other carcinomas

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• Always interpret molecular findings in context of

• morphology

• clinical features

Molecular Diagnosis

Additional Approaches

• Gene expression profiling

• new antibodies

• predict behavior

• Comparative genomic hybridization

• copy numbers

• Epigenetics

• DNA methylation, miRNAs, sRNAs

• Protein expression profiling

Next Generation Sequencing

• Identifies molecular events

• Targetable mutations

• single-nucleotide variants,

• small insertions & deletions

• copy number variation

• complex structural variations

• Fusion genes

• Gene Signatures

Jour 2014; van de Rijn 2014

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CINSARC

• Complexity INdex in SARComas

• Gene expression signature (67 genes)

• Frozen tissue in microarray

• NGS - RNA sequencing in paraffin

• Can predict metastasis in

• leiomyosarcoma, UPS, DDL

• synovial sarcoma

• CDCA2 or KLF14

– Small molecule inhibitors

Chibon 2010; Lagarde 2013; Lesluyes 2016

Predicting Behavior - Prognostic Factors

• Age

• Site

• Size

• Grade

• Stage

• Proliferation markers

• Differentiation markers

French Cancer Centers Grading System

• Differentiation score- resembles normal- definite type- pleomorphic or undifferentiated

• Mitotic count (/10hpf)0-9, 10-19, 20+

• Necrosis0, <50%, >50%

• GRADE:2,3 = G1; 4,5 = G2; 6,7,8 = G3

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Caveats

Tumors which are intrinsically

high grade

Rhabdomyosarcoma

Ewing sarcoma / PNET

Soft tissue osteosarcoma

Mesenchymal chondrosarcoma

Epithelioid sarcoma

Clear cell sarcoma

Grade does not always

correlate with

outcome/behavior

Angiosarcoma

MPNST

Grading

Take home messages

• Clinical context

• Methodical approach

• Not everything in soft tissue is mesenchymal

THE END

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