Desterrando El Término Ewing-Like Sarcoma: ¿Qué Entidades Se Cobijaban Bajo Esa Denominación?

Desterrando el término Ewing-like sarcoma: ¿Qué entidades se cobijaban bajo esa denominación?

Sílvia Bagué Servei de Patologia Hospital de la Santa Creu i Sant Pau Universitat Autònoma de Barcelona #SEOM20 No disclosures Small round cell sarcomas (SRCS) - Group of malignant neoplasms sharing histological similar features - Mainly in children & young adults - High-grade by definition. Often “translocated-sarcomas”

• Ewing sarcoma • “Ewing-like” sarcomas • Desmoplastic SRCT • Alveolar rhabdomyosarcoma • Poorly diff sinovial sarcoma • Mesenchymal chondrosarcoma • High-grade myxoid liposarcoma • Small cell osteosarcoma • Undiff sarcoma with round cell morphology (USRCS)

#SEOM203 Ewing sarcoma • Most common round cell sarcoma • 1st - 2nd decade • 85% diaphysis-metaphysis long bones > pelvis, ribs, chest wall (‘Askin’) • 15% extraeskeletal (adults) • Key morphologic features: uniform monotonous round cells, fine chromatin, inconspicious nucleoli, scant clear to pale cytoplasm • Key immunohistochemical stains: strong and diffuse membranous CD99 expression; NKX2+, PAX7+ • Genetics: fusion between EFT genes (FUS, EWSR1) and TAF15 genes and ETS transcription factor family members (Fli-1, ERG, ETV1, ETV4, FEV, E1AF, ZSG)

85-90% t(11;22)(q24;q12) EWSR1- FLI1 fusion gene 5-10 % t(21;22)(q22;q12) EWSR1-ERG fusion gene

CD99 FISH EWSR1 #SEOM204 Desmoplastic small round cell tumor Clinical history Boy, 12 y-o. Intraabdominal mass

#SEOM205 DSRCT: IHC & genetics Malignant round cell tumor with desmoplastic stroma, poliphenotypic differentiation and translocation t(11;22)(p13;q12) with EWSR1-WT1 fusion gene

WT1 Ker

FISH: EWSR1 + Vim DesminDesmin #SEOM206 STT other than Ewing carrying EWS translocation

Sbaraglia M et al. Virchows Archiv. 2019 7 Human Molecular Genetics, 2006 Vol.15, No.13

Clin Cancer Res, 2009; 15(7): 2259

Nature Genetics, 2012 Vol.44, No 4 #SEOM208 Classification of soft tissue & bone sarcomas

Tumours of uncertain differentiation

Acral fibromyxoma Intramuscular myxoma Juxta-articular myxoma Deep (aggressive) angiomyxoma Atypical fibroxanthoma Angiomatoid fibrous histiocytoma Ossifying fibromyxoid tumour Myoepithelioma, myoepithelial carcinoma, and mixed tumour Pleomorphic hyalinizing angiectatic tumour of soft parts Haemosiderotic fibrolipomatous tumour Phosphaturic mesenchymal tumour Synovial sarcoma Epithelioid sarcoma Alveolar soft part sarcoma Clear cell sarcoma of soft tissue Extraskeletal myxoid chondrosarcoma Malignant mesenchymoma Desmoplastic small round cell tumour Extrarenal rhabdoid tumour PEComa Intimal sarcoma

Undifferentiated/unclassified sarcomas

Undifferentiated round cell EWSR1-non ETS (PATZ1, NFATC2), CIC-DUX4, BCOR Undifferentiated spindle cell sarcoma Undifferentiated pleomorphic sarcoma (UPS)

WHO 2013 #SEOM209 Classification of soft tissue & bone sarcomas

Tumours of uncertain differentiation

Undifferentiated/unclassified sarcomas

... “ theRound number cell EWSR1 of cases-non with ETS such(PATZ1, fusions NFATC2), is, howeverCIC-DUX4,, stillBCOR small and it remains to be Spindleseen wether cell they represent one or more separate entities, or wether they Pleomorphicare (UPS) better classified as variants of Ewing sarcoma...” “Ewing-like sarcomas” WHO 2013 #SEOM2010 Different molecular profile (RNA sequencing data)

Clustering of BCOR-CCNB3 sample (red) with BCOR ITD (orange) and BCOR-MAML3 (purple) into a group, separate from Ess (blue) and CIC-rearranged sarcomas (green) Kao YC et al. Am J Surg Pathol, Vol 42, No 5, May 2018 11 Different molecular profile (DNA methyation)

Koelsche et al. Journal of Cancer Research and Clinical Oncology 2019 #SEOM2012 ‘Transcriptomic definition of molecular subgroups of small round cell sarcomas’

New clinical entities or merely “groups” of patients?

Watson S et al. J Pathol 2018 May;245(1):29-40. doi: 10.1002/path.5053. 13 Classification of soft tissue & bone sarcomas

Tumours of uncertain differentiation

Intramuscular myxoma Juxta-articular myxoma Deep (aggressive) angiomyxoma Atypical fibroxanthoma Angiomatoid fibrous histiocytoma Ossifying fibromyxoid tumour Myoepithelioma, myoepithelial carcinoma, and mixed tumour Pleomorphic hyalinizing angiectatic tumour of soft parts Haemosiderotic fibrolipomatous tumour Phosphaturic mesenchymal tumour NTRK-rearranged spindle cell neoplasm (emerging) Synovial sarcoma Epithelioid sarcoma Alveolar soft part sarcoma Clear cell sarcoma of soft tissue Extraskeletal myxoid chondrosarcoma Desmoplastic small round cell tumour Extrarenal rhabdoid tumour PEComa, including angiomyolipoma Intimal sarcoma Undifferentiated sarcoma

Undifferentiated small round cell sarcomas of bone and soft tissue

Ewing sarcoma Round cell sarcoma with EWSR1-non-ETS fusions CIC-rearranged sarcoma Sarcoma with BCOR genetic alterations WHO 2020 #SEOM2014 CIC - Rearranged Sarcomas

• 3-5% round cell sarcomas adult and pediatric population • 70% of SRCSs lacking EWSR1 or FUS rearrangements • CIC gene fusions: CIC-DUX4 (~95%), other partners (5%): LEUTX, DUX10, NUTM1, NUTM2, FOXO4 ...

• 90% deep soft tissue (extremities and trunk > retroperitoneum, H&N, visceral) • Bone involvement infrequent (< 5% cases) • Children, young adults (2n decade); slight male predominance

• Morphologic features: - Sheets of round cells in a fibrotic to myxoid background - More nuclear atypia, prominent nucleoli “Atypical Ewing sarcomas” - Necrosis (geographic) common. Numerous mitoses - Focal rhabdoid, spindled or epithelioid areas may be present

• IHQ: patchy, weak expression for CD99, NKX2.2 -; WT1+, ETV4+

• Molecular diagnosis is challenging (~20-40% false negative results by FISH/ RT-PCR) • Highly aggressive (poorer outcome than ES and BCOR sarcomas) (5-year OS 43%) WT1 ETV4

Carter CD et al. Surg Pathol Clin.2019 doi: 10.106/j.path.2018.10.008 15 Am J Surg Pathol 2017;41:941-949 Source: Sbaraglia M et al. Virchows Archiv. 2019

• Slight male predominance • Peak in 2nd decade • More common in soft tissue Round cell morphology Epithelioid morphology • Trunk > limbs > viscera > bone • Round cell morphology, spindling, epithelioid, myxoid change • CD99 focal • FOXO4, LEUTX, NUTM1, NUTM2A

Focal spindling Abundant necrosis 16 Source: Le Loarer F et al. Am J Surg Pathol 2019 17 17 BCOR-Rearranged Round Cell Sarcomas

• Uncommon primitive round and spindle cell sarcoma (4% SRCS) • Pediatric and young adult population. Male predominance (85%) • More common in bone (60%). Pelvis, long bones • Various BCOR alterations with different groups/entities:

1. BCOR fusion sarcomas: 90% BCOR-CCNB3 Others: BCOR-MAML3; ZC3H7B-BCOR (HG-ESS, ossifying fibromyxoid tumor) 2. BCOR ITD: Primitive myxoid mesenchymal tumor of infancy / infantile URCS

• Morphologic overlap. Key morphologic features: - Delicate branchig capillary network - Myxoid matrix - Mixed round to spindle cells (12% purely spindle. lacking round cells features)

• IHC (non-specific): BCOR, BCL-6, cyclin D1, TLE1, SATB2. Overlap with SS!! WT1_ve. CCNB3 (nuclear) in tumors with BCOR-CCNB3 fusion • Treatment? Prognosis: 5-year OS ~ 75% • Better outcome than ES and CIC 18 BCOR-Rearranged Round Cell Sarcomas

• Peak in 2nd decade • Male predominance (85%) • More common in bone (2/3) Round cell morphology Spindle cell morphology • Round to spindle cell morphology (between ES and SS)

Biphasic morphology BCOR Source: Sbaraglia M et al. Virchows Archiv. 2019 19 BCOR-Rearranged Round Cell Sarcomas

BCOR better outcome than ES and CIC

Am J Surg Pathol, Vol 42, No 5, May 2018 20 RCS with EWSR1-non ETS fusions

EWSR1/NFATc2-rearranged sarcomas • Extremely rare! (56 published cases) [Perret R et al. Modern Pathology 2020] • Strong male predilection (5:1) • 4th decade (older than ES) • Long bones > soft tissue (4:1) • Histology: two patterns A/ cords and clusters of small to medium round cells in a myxohyaline to fibrous matrix (“myoepithelioma- like”) B/ poorly differentiated round cell pattern • CD99 +, CK +, NKX2.2 +,ETV4 -,WT1 -/+ FUS-NFATc2 • Long bones EWSR1–PATZ1 • Deep soft tissue and CNS. Sclerotic. Myogenic markers

Source: Sbaraglia M et al. Virchows Archiv. 2019 21 Source: Perret R et al. Modern Pathology 2020#SEOM20 22 Genetics of Ewing sarcoma and “Ewing-like” sarcomas

Sbaraglia M et al. Virchows Archiv. 2019 23 ES & “Ewing-like” sarcomas

Substantial morphologic overlap... 24 ES CIC

BCOR

NFATc2

...but IHC, molecular and clinical differences 25 Clinicopathologic features of round cell sarcomas

Davis JL et al. Curr. Treat. Options in Oncol 2020 #SEOM2026 Outcome and common treatment paradigms for round cell sarcomas

Davis JL et al. Curr. Treat. Options in Oncol 2020 #SEOM2027 Distribution of gene fusions in Ewing sarcoma and Genes Chromosomes Cancer 2020;59:525–534. round cell sarcoma with EWSR1-non-ETS fusions 28 Clinical data + imaging FNA, CNB Specimen work up

FNA CNB H&E Frozen tissue em_sample (biobanking, trials) IHC

CD99 TFE3 Molecular pathology

Final diagnosis FISH RT- PCR 29 NGS and Sarcomas

. Validation of classification - accurate diagnosis provides appropriate clinical decision making . Identification of new (more solid) diagnostic markers - only in context with morphology - same genetic alterations in unrelated entities . Identification of new tumor entities - i.e. novel gene fusions in round cell sarcomas . Identification of new potential targets - patients recruitment for trials

30 Key points

. CIC/BCOR & non-ETS-fused round cell sarcomas currently no more classified as “Ewing-like” sarcomas . Exceedingly rare . Now recognized as independent morphologic/molecular entities . Morphologic clues pointing toward their diagnosis include cell spindling, nuclear atypia, and stromal changes (subtle) . CIC worse outcome . BCOR more indolent clinical course . Not very good response to Ewing-type chemotherapy . Referral to expert rare cancer centers / networks (molecular confirmation) . Undifferentiated / unclassified SRCS still exist !! 31

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