Disclosure of Relevant Financial Relationships

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1 Neuropathology Evening Specialty Conference Disclosure of Relevant Financial Relationships The USCAP requires that anyone in a position to influence or control the content of all CME activities disclose any relevant relationship(s) which they or their spouse/partner have, or have had within the past 12 months with a commercial interest(s) [or the products or services of a commercial interest] that relate to the content of this educational activity and create a conflict of interest. Complete disclosure information is maintained in the USCAP office and has been reviewed by the CME Advisory Committee. Cristina Antonescu, MD Department of Pathology No conflict of interest to disclose. Clinical History 66 year old man with a left neck swelling and pain in the left cheek while eating. He had a long history of smoking. Intra operatively the lesion involved the parapharyngeal space and was resected marginally. He received post op radiation therapy but recurred locally and distantly and succumbed of disease one year after the initial diagnosis. Clinical Detail Omitted 45 years ago (age of 20) he received radiation to the neck and chemotherapy for a diagnosis of lymphoma 1

2 CT scan: parapharyngeal mass displacing major vessels around periphery Gross Exam: white tan fleshy mass with areas of hemorrhage & necrosis Histology: Fascicular growth pattern Histology: Monomorphic spindle cells 2

3 Histology: Lower cellularity myxoid component Histology: Areas of chondrosarcoma component Histology: Areas of chondrosarcoma component IHC: S100 protein in the spindle cell component Other IHC: focally positive for CD34, negative for TLE1, CK 3

4 IHC: S100 protein chondrosarcoma component IHC: Loss of H3K27Me3 expression in both components Diagnosis Malignant Peripheral Nerve Sheath Tumor (MPNST) with Chondrosarcomatous Divergent Differentiation, Radiation Induced Outline Diagnostic criteria for MPNST Differential diagnosis of MPNST in the H&N location RT induced MPNST Recent genetic developments in MPNST H3K27me3 loss of expression as an adjunct ancillary tool 4

5 MPNST Background Rare <5% of sarcomas Neuroectodermal rather than mesenchymal lineage Model of tumor progression: Neurofibroma >Atypical Neurofibroma > LG MPNST > HG MPNST Types: 50% NF1 associated 40% sporadic 10% Radiation induced MPNST Radiology & Gross Imaging: heterogeneous contrast enhancement fusiform /globoid Gross: >10 cm infiltrative, unencapsulated cream colored MPNST arising from a Plexiform NF (tibial nerve) in a 24/M NF1 patient MPNST Growth Patterns: Herringbone 5

6 Marbled Appearance Geographic Necrosis MPNST Monomorphic Spindle cell Histology Rare Nuclear Pleomorphism Relaxed Criteria in Diagnosis of NF1 associated HG MPNST Nc Pleom High Mitotic Activity Areas of Anaplasia/ Nuclear Pleomorphism 6

7 MPNST IHC S100 protein: 40 50% SOX10: 50 60% MPNST with Divergent Differentiation 15% of MPNST 60% are associated with NF1 Types: mesenchymal and epithelial Metaplastic plasticity of the neoplastic Schwann cells Other markers: Loss of C terminal Neurofibromin (Reuss DE, Acta Neuropathol 2014) Malignant Triton Tumor Glandular MPNST Chromogranin 7

8 Cranial Nerves/Head and Neck MPNST Spindle Cell Neurotropic Melanoma Frequent nerves: vagus, trigeminal, vestibular Intra cranial MPNST very rare, occur from brain neurovascular bundles Benign precursor: neurofibroma and schwannoma (Scheithauer BW, Amer J Surg Pathol 2009) Differential diagnosis: neurotropic melanoma Preferential in skin, lip, visible mucosa Neurotropic Melanoma Sinonasal MPNSTs distinguished from Biphenotypic Sinonasal Sarcoma Low grade sinonasal MPNST? Sinonasal fibrosarcomas, malignant schwannomas, and Triton tumors. A clinicopathologic study of 67 cases. Heffner DK, Cancer 1992 Sinonasal Triton Tumors? of 13 cases none were NF1 associated Prognostic factors for the malignant triton tumor of the head and neck. Terzic A, Head Neck 2009 Sparring the nerve fascicles 8

9 PAX3 MAML3 Biphenotypic Sinonasal Sarcoma monomorphic spindle cell tumor with dual neural and myogenic phenotypes PAX3 NCOA1 variant Biphenotypic Sinonasal Sarcoma IHC: S100 + Actin pos; SOX10 neg Differential diagnosis: Cellular schwannoma Synovial sarcoma MPNST Triton Tumor MyoD1 Myogenin Wang X, Nat Genet 2014 Scattered rhabdomyoblasts Huang SC, Amer J Surg Pathol 2016 Post radiation HG MNPST Location: most occur in trunk or axial location Poor prognosis (intrinsic vs location) Smaller tumor size compared to NF1/sporadic MPNST Main Reasons for Diagnostic Problems in MPNST No hx of NF1 Cannot demonstrate a nerve origin No pre existent neurofibroma identified Atypical histologic features: nuclear pleomorphism Non specific immunoprofile (negative S100, SOX10) LaFemina J, Ann Surg Oncol

10 MPNST outside NF1 setting diagnosis of exclusion Undifferentiated phenotype, shared by other tumors (synovial sarcoma, fibrosarcoma, spindle cell melanoma) Lack pathognomonic IHC and Molecular markers (limited if any) schwannian differentiation by IHC and EM High inter observer variability, even among experts Genetics in NF1 related NF & MPNST Neurofibroma: NF1 biallelic inactivation (germline and somatic) other mutations are rarely found Atypical neurofibromas (presumed MPNST precursors) additional CDKN2A deletions (Beert E, Genes Chr Cancer 2011) MPNST: NF1 inactivation CDKN2A(p16/p14) homozygous deletions (50%) Loss of Function Somatic Alterations in PRC2 complex PRC2: polycomb repressive complex 2 EED SUZ12 (JJAZ1) EZH1/2 Role: chromatin impaction and gene silencing di/tri methylation of Lys27 of histone H3 (H3K27me2/3) Mutations in EED & SUZ12 occur in 80% of HG MPNST NF1 EED SUZ12 CDKN2A TP53 Lee W, Nature Genetics 2014 Lee W, Nature Genetics 2014; Zhang M, Nature Genetics 2014; De Raedt T. Nature

11 Mutations in EED & SUZ12 in HG MPNST Incidence varied with the MPNST type 70% NF1 associated 92% Sporadic 90% RT induced PRC2 deficient MPNST complete loss of H3K27me3 H3K27me3 is the effector of the PRC2 pathway H3K27me3 IHC correlates with PRC2 genetic status: Anti H3K27me3 rabbit polyclonal Ab (Millipore) Co existed with abnormalities in NF1 (72%) CDKN2A (p16)(81%) Lee W, Nature Genetics 2014 Lee W, Nature Genetics 2014 Loss of H3K27me3 ancillary marker in MPNST? Am J Surg Pathol 2016; 40: Prieto Granada, Amer J Surg Pathol 2016 Anti H3K27me3 monoclonal Ab: clone C36B11 Cell Signaling MPNST cohort with known NF1/CKDN2A/PRC2 genetic alterations Sensitivity in MPNST subsets Specificity with other spindle cell neoplasms Schaefer, Modern Pathol 2016 Anti H3K27me3 rabbit polyclonal Ab Millipore Sensitivity in MPNST subsets Specificity with other spindle cell neoplasms Modern Pathology 2016; 29:

12 Loss of H3K27me3 Expression in NF1 associated MPNST N= 60% of cases Loss of H3K27me3 Expression in MPNST retained in adjacent Neurofibroma (NF) H3K27me3 loss is not seen in NF or atypical NF PRC2 inactivation may occur in the progression to HG MPNST MPNST Prieto Granada, Am J Surg Pathol 2016; 40: NF Prieto Granada, Am J Surg Pathol 2016; 40: Retained H3K27me3 Expression in NF1 MPNST N= 40% of cases Loss of H3K27me3 Expression in Sporadic MPNST N=95% selected independent to the genetic abnormalities typical morphology (monomorphic spindle, fascicular growth) compatible IHC? Additional genetic alterations are required for tumor progression 12

13 Loss of H3K27me3 Expression in RT associated MPNST N=91% selected independent to the genetic abnormalities typical morphology (monomorphic spindle, fascicular growth) compatible IHC MPNST with Divergent Differentiation Heterogeneity in H3K27me3 expression MPNST HG MPNST with leiomyosarcomatous divergent differentiation Loss of H3K27me3 Expression in MPNST Prieto Granada (69%) vs Schaefer (51%) studies Loss of H3K27me3 Expression is related to MPNST grade Prieto (n=68) Monoclonal Ab Schaefer (n=100) Polyclonal Ab NF NF1 MPNST Sporadic RT induced 0 60% 95% 91% 0 70% 49%* 100% Schaefer et al (equally divided among 3 tier grade) 29% LG MPNST 59% Intermediate grade MPNST 83% HG MPNST MSKCC/Prieto Granada selected independent to the genetic abnormalities typical morphology (monomorphic spindle, fascicular growth) compatible IHC Brigham/Schaefer *MPNST Tier 1 / Tier 2 based on the diagnostic confidence level, supporting IHC profile Prieto Granada et al (95% were HG MPNST, 2 tier system) 1/3 (33%) LG MPNST 72% HG MPNST 13

14 Epithelioid MPNST No association with NF1 Strong S100 protein expression, INI1 loss Distinct genetic abnormalities from conventional MPNST, lacking NF1/CDKN2A/PRC2 loss (Lee W, Nature Genetics 2014) S100? Different Pathologic Entity Retained H3 expression Loss of H3K27me3 Expression Appears Specific to MPNST Prieto Granada, Amer J Surg Pathol 2016 Melanoma Pure desmoplastic (n=37) Mixed desmoplastic (n=11) Spindle (n=5) Synovial sarcoma (n=113) GIST (n=120) DDLS (n=44) Myxofibrosarcomas (n=63) Schaefer, Modern Pathol 2016 Spindle cell melanoma (n=20) Synovial sarcoma (n=20) Leiomyosarcoma (n=20) Mg SFT (n=20) GIST (n=10) Spindle cell RMS (n=10) FS DFSP (n=10) RT induced sarcoma (n=20) 10% loss of H3 RT induced HG MPNST with nuclear pleomorphism Loss of H3K27me3 expression Summary Combined inactivation of NF1/CDKN2A/PRC2 is critical for the pathogenesis of most HG MPNST Loss of H3K27me3 expression is a useful marker in challenging MPNST diagnoses, outside the NF1 These recent genetic advances of shared PRC2 inactivation across NF1 related, post Radiation and sporadic MPNSTs support a single pathologic entity 14

15 Summary H3K27me3 expression is associated with tumor grade, being lost preferentially in HG MPNST and retained in LG lesions NF1 related MPNST had the lowest rate of PRC2 genetic abnormalities suggesting alternative genetic events that cooperate with NF1/CKDN2A Epithelioid MPNSTs do not share the PRC2 inactivation and retain H3K27me3 expression, in keeping with a different pathogenesis James Woodruff ( ) Bernd Scheithauer ( ) 15

16 James Woodruff (2001) Differential Diagnosis Immunoprofile S100 SOX10 H3 FISH/NGS HG MPNST +/ +/ lost NF1 CDKN2A SUZ12, EED MSS retained SS18 Spindle cell melanoma retained NF1 16

17 Robert Erlandson and James Woodruff 17