Special Lecture AP sir- Paediatric round cell tumors copy.pptx

Pediatric round cell tumour

1. Paediatric round cell tumors Presenter – Dr Amrit Pal Singh Guide – SLC Vineet Kotian

2. PAEDIATRIC ROUND CELL TUMORS DEFINITION - Small Round Cell Tumors are a heterogeneous group of malignant neoplasms that share a similar microscopic appearance: they are composed of undifferentiated or poorly differentiated cells that are small, round, hyperchromatic , and have scant cytoplasm . These tumors most commonly affect children and adolescents , and due to their overlapping morphology, immunohistochemistry, cytogenetics, and molecular studies are essential for accurate diagnosis. TYPES Medulloblastoma Retinoblastoma Pineoblastoma Hepatoblastoma Rhabdomyosarcoma DSRCT Ewing Sarcoma Small Cell Osteosarcoma Neuroblastoma Nephroblastoma Clear Cell Sarcoma of Kidney Lymphoma

3. MEDULLOBLASTOMA World Health Organization Grade 4 Most common CNS embryonal tumor that arises in the cerebellum or in the roof of the fourth ventricle It is most common in children but also occurs in young adults; it is rare in patients older than 35 years Signs and symptoms of increased intracranial pressure (headache, nausea, vomiting) It is often associated with isochromosome 17q (one chromosome composed of two long arms of chromosome 17) S preads along CSF pathways, a bout 5% of medulloblastomas metastasize to a systemic location, particularly to bone GROSS - The posterior fossa mass  near the midline of cerebellum  and extending into the  fourth ventricle  above the  brainstem

4. MEDULLOBLASTOMA - MICROSCOPY Classic medulloblastoma - Syncytial arrangement of small round blue undifferentiated cells, Rosettes with cores filled with fibrils (Homer-Wright rosettes) Desmoplastic/Nodular Medulloblastoma - They have both abundant reticulin and crowded, proliferating cells. Segregated by the desmoplasia are pale islands of tissue that lack reticulin and are less crowded with cells (reticulin-free zones Medulloblastoma with Extensive Nodularity - Expanded lobular architecture due to reticulin free nodular zones becoming enlarged and rich in neuropil-like tissue. This variant is associated with favorable outcome. Large cell / anaplastic medulloblastoma - Anaplasia with marked nuclear pleomorphism, high mitotic count and high apoptotic count, Nuclear molding and cell wrapping

5. MEDULLOBLASTOMA IMMUNOHISTOCHEMISTRY The neuronal phenotype of medulloblastoma is demonstrated by positivity of neoplastic cells for synaptophysin Regions of glial differentiation can be noted histologically and confirmed by GFAP expression. Occasional nonglial differentiation, like myogenic, melanocytic, reflects its multipotential nature. Nuclear  SMARCB1 / INI1  and  SMARCA4  are retained

6. MEDULLOBLASTOMA Medulloblastomas can also be subclassified into three distinct molecular subgroups: WNT-activated, SHH-activated, and non-WNT/non-SHH Molecular subgroups Molecular alterations % of occurrence Associated histological subtype Overall 5 year survival WNT activated CTNNB1 mutation Monosomy 6 10% Classic 95% SHH activated If TP53 wild type – Mutation in PTCH1, SMO or SUFU 30% Desmoplastic 75% If TP53 mutated – Amplification of GLI2, MYCN or SHH Non WNT/ Non SHH MYC amplification Isochromosome 17q 60% Classic 50%

7. RETINOBLASTOMA Most frequent intraocular malignancy of childhood, Most occur sporadically, about 30-40% are inherited. Sites - Sporadic retinoblastoma usually unilateral eye, Inherited retinoblastoma often bilateral eyes. Can be trilateral ( pineoblastoma ) or very rarely quadrilateral ( pineoblastoma and suprasellar primitive neuroectodermal tumor ) Average age at diagnosis is 2 years, but some patients may be older than 5 years Biallelic inactivation of RB1 gene, Non heritable RB arises from somatic mutation occurring on both alleles of RB1 gene in the developing retina. Heritable RB arises from inheritance of atleast one germline mutation alongwith an acquired RB1 somatic mutation. Clinically - White pupil (leukocoria), strabismus, decreased visual acuity, glaucoma, or a red and painful eye Grossly - C reamy white with chalky areas of calcification and yellowish necrotic regions. RB may grow inward toward the vitreous cavity (endophytic RB) or outward toward the choroid (exophytic RB), or a mixed pattern. Rarely, RB thickens the retina diffusely without forming a discrete mass (diffusely infiltrative RB)

8. RETINOBLASTOMA MICROSCOPY – Varies with degree of differentiation. Hyperchromatic small round blue cells with scant cytoplasm arranged in sheets, nests and trabeculae Calcification and perivascular ischemic necrosis common Flexner- Wintersteiner rosettes (most common) - Central lumen with basally located nuclei Homer Wright rosettes (less common in retinoblastoma) - Lack of central lumen, t umor nuclei displaced away from eosinophilic center Fleurettes - Tumor cells arranged side by side with central lumen, Resembles fleur de lis Histologic grade: G1: tumor with areas of retinocytoma (fleurettes or neuronal differentiation accounting for more than half of tumor) G2: tumor with many rosettes, Flexner- Wintersteiner or Homer Wright rosettes accounting for more than half of tumor G3: tumor with occasional rosettes, Flexner- Wintersteiner or Homer Wright rosettes accounting for less than half of tumor G4: tumor with poorly differentiated cells without rosettes or with extensive areas of anaplasia

9. RETINOBLASTOMA IMMUNOHISTOCHEMISTRY Positive for SOX2, MAP2, NSE, Synaptophysin, Retinoblastoma associated protein ( pRb ) Negative for CD99, lymphocyte markers ( CD45 ,  CD3 ,  CD20 , etc.), GFAP  (stains reactive stromal astrocytes in background and peritumoral tissue; negative in tumor cells) DIFFERENTIAL DIAGNOSIS Astrocytoma: Generally not small round blue cell pattern, GFAP positive Leukemia /  lymphoma : Calcifications not seen, Necrosis rare, CD45  positive, B cell (e.g.  CD19 ,  CD20 ,  PAX5 ) or T cell (e.g.  CD3 ,  CD5 ,  TdT ) markers positive Massive retinal gliosis : No rosettes or fleurettes, No necrosis or calcifications

10. RETINOBLASTOMA RB may invade the optic nerve & extend along it toward the brain, or individual neoplastic cells may reach the CSF by penetrating into the subarachnoid space surrounding the optic nerve. The extent of RB into the optic nerve is classified as none, anterior to lamina cribrosa, at lamina cribrosa, posterior to lamina cribrosa but not to end of nerve, or to cut end of optic nerve (positive margin). RBs infrequently spread extraocularly through scleral channels Poor prognostic factors include optic nerve involvement, choroid invasion, and extraocular extension. Other histologic features of prognostic significance include tumor size, seeding of vitreous, degree of differentiation, involvement of anterior segment, growth pattern, and involvement of the sclera.

11. PINEOBLASTOMA Pineoblastoma is a malignant supratentorial midline primitive neuroectodermal tumor of pineal gland. Pineoblastoma represents ~30 - 35% of all pineal parenchymal tumors Pineoblastoma typically arise in children / adolescents, with the overall median age of 6 years Sites - Pineal gland, Cerebrospinal fluid (CSF) dissemination in 25 - 30% of patients as well as distant spinal metastases Clinically - Patients typically present with features of increased intracranial pressure and obstructive hydrocephalus (headache, nausea, vomiting, papilledema). If the tumor compresses the superior colliculus, patients may present with Parinaud syndrome (upward gaze palsy) Young patient age, disseminated disease at diagnosis and subtotal surgical resection are important negative prognostic factors

12. PINEOBLASTOMA GROSS - Soft, friable, tan-pink to tan-gray mass, may show areas of hemorrhage or necrosis MICROSCOPY Sheets of crowded, highly pleomorphic, undifferentiated appearing neoplastic cells, manifesting focal nuclear molding, with a high mitotic rate resembling medulloblastoma or embryonal tumors. Homer-Wright rosettes and less commonly Flexner- Wintersteiner rosettes are seen

13. PINEOBLASTOMA IMMUNOHISTOCHEMISTRY Positive for Synaptophysin, Chromogranin A (variable), NSE, Neurofilament (variable), INI1 (SMARCB1), BRG1 (SMARCA4), CRX Negative for GFAP, Olig2, Cytokeratins DIFFERENTIAL DIAGNOSIS Pineal parenchymal tumor of indeterminate malignancy less cytologic atypia and lower mitotic activity, minimal to no rosette formation and no necrosis KBTBD4  mutation, which is absent in pineoblastoma Medulloblastoma Localized in the posterior fossa by definition May harbor alterations in SHH and WNT pathways Lacks CRX immunohistochemical expression Atypical teratoid / rhabdoid tumor Loss of  INI1 (SMARCB1)  expression or  BRG1 (SMARCA4)  expression Variably positive for  GFAP  and  cytokeratins

14. HEPATOBLASTOMA Most common primary liver tumor in children, A rises from primary hepatoblasts or multipotent hepatic progenitor cells. 90% present within first 3 years of life, Adult tumors are very rare, Slight male predominance. Majority (80%) of cases are sporadic. Associated abnormalities (15-20%) include F amilial A denomatous P olyposis ( APC  mutations), Beckwith-Wiedemann syndrome, trisomy 18, horseshoe kidney, renal dysplasia, Meckel diverticulum, cleft palate. Clinically - abdominal mass, pain, anorexia and weight loss may be reported, Jaundice is an uncommon feature. Chromosomal abnormalities – Gain of Ch 2, 8 and 20 & Loss of Ch 18. About 80% of HBs have CTNNB1 mutation, NFE2L2, TERT mutations. GROSS - MC solitary masses (80%), involving the right lobe of liver (60%). Well circumscribed, may be partially encapsulated, are nodular with bulging cut surface. Necrosis and hemorrhage are present in posttreatment specimens, If osteoid is present, the texture is firm and gritty.

15. HEPATOBLASTOMA - MICROSCOPY Classified as epithelial (56%) or mixed epithelial and mesenchymal (44%). Most HBs show a mixture of epithelial patterns but single patterns are found in 20% of cases. Pattern Architecture N:C ratio Nucleolus Pleomorphism Mitosis (per 10 hpf ) Fetal (31%) Trabeculae, 2-3 cell thick, light dark pattern Low Small Minimal < 2 Embryonal (19%) Sheets, ribbons, acini, pseudorosettes High Large Frequent >2 Macro-trabecular (3%) Trabecular, > 10 cell thick Variable Variable Variable Variable Small cell undifferentiated (3%) Discohesive sheets of small uniform cells, + mucoid stroma Highest Variable Minimal >2 Cholangioblastic (rare) Duct embedded in mesenchymal structures High Variable Variable Variable

16. HEPATOBLASTOMA - MICROSCOPY Mixed epithelial and mesenchymal types (44%) Pattern Architecture N:C ratio Nucleolus Pleomorphism Mitosis (per 10 hpf ) Non teratoid (34%) Spindle oval cells, frequent osteoid formation, rarely other differentiated sarcomatous elements High Variable Minimal < 2 Teratoid (10%) Shows multiple lines of differentiation including neural , glial, neuroendocrine, gland formation, mucinous or squamous. Variable Variable Variable -

17. HEPATOBLASTOMA – IHC Pattern IHC Fetal + ve for Hepar1, Arginase, AFP, Negative or weak cytoplasmic staining for Glypican3, Beta Catenin shows scattered nuclear positivity, less than what seen in embryonal pattern Embryonal + ve for Hepar1, Arginase, Glypican3 and AFP, Beta catenin shows nuclear accumulation often with abnormal cytoplasmic staining Macrotrabecular + ve for Hepar1, Arginase, AFP and often Glypican3 Small cell undifferentiated - ve for Hepar1, Arginase and AFP, but Glypican3 can be focal positive. Usually negative for Beta Catenin nuclear accumulation but can be very focally positive. INI should be performed to rule out rhabdoid tumor which can closely mimic HB and shows diffuse loss of nuclear staining Cholangioblastic CK7 and CK19 positive, Nuclear accumulation of Beta Catenin

18. HEPATOBLASTOMA - DDs Hepatocellular carcinoma Resembles pleomorphic fetal pattern and macrotrabecular variant of hepatoblastoma No mesenchymal or fetal components, Uncommon in children Larger, more pleomorphic tumor cells, trabeculae often > 2-3 cell thick No extramedullary hematopoiesis Associated cirrhosis Metastatic tumors More common than hepatoblastoma, primary tumor cells should not resemble hepatocytes Wilms tumor , neuroblastoma, rhabdomyosarcoma, Lymphoma. Rhabdoid tumor Rhabdoid morphology, without the diversity of patterns Positive for  desmin

19. HEPATOBLASTOMA – STAGING & PROGNOSIS PRETEXT (PRE-Treatment EXTent of tumor) staging system is the recommended by the Pediatric Hepatic International Tumor Trial PRETEXT group describes the extent of tumor in the liver and therefore the amount that must be surgically removed Liver is divided into 4 sections: left lateral section ( Couinaud segments 2 and 3), left medial section ( Couinaud segments 4a and 4b), right anterior section ( Couinaud segments 5 and 6) and right posterior section ( Couinaud segments 6 and 7) PRETEXT I: 1 section is involved and the adjoining are free PRETEXT II: 1 or 2 sections are involved and 2 adjoining are free PRETEXT III: 2 or 3 sections are involved and no 2 adjoining sections are free PRETEXT IV: all sections are involved

20. HEPATOBLASTOMA – STAGING & PROGNOSIS Multifocal disease, extrahepatic and unresectable vascular involvement, tumor rupture and metastasis at diagnosis are factors of bad prognosis Age < 1 year (good prognosis) versus age > 6 years (worse prognosis) Normal or low levels of alpha fetoprotein (AFP) are associated with aggressive course Serum AFP reduction during treatment is a good prognosis and indicator of response to treatment Pure fetal pattern with low mitotic activity is related to good prognosis and small cell undifferentiated pattern is associated with bad prognosis Based on staging system, metastases and AFP levels, 5 prognostic groups have been established, with group 1 exhibiting the best prognosis and group 5 the worst GROUP PRETEXT GROUP METASTASIS AT DIAGNOSIS S.AFP LEVELS ( microgm /L) 1 I or II No >100 2 III No >100 3 IV No >100 4 Any Yes >100 5 Any Any Less than/Equal to 100

21. RHABDOMYOSARCOMA Malignant mesenchymal tumor with skeletal muscle differentiation Three subtypes Embryonal – MC children Alveolar – Adoloscents and young adults Pleomorphic – Middle aged to elderly

22. ALVEOLAR RHABDOMYOSARCOMA High grade, cellular, round cell sarcoma with evidence of skeletal muscle differentiation Affects adolescents and young adults, Peak incidence is between 10 and 25 years. M = F Commonly involves deep soft tissue of extremities, typically forearm, Other sites include head and neck, trunk, paraspinal, pelvic, genitourinary regions and retroperitoneum t(2;13)(q36;q14):  PAX3::FOXO1  in 70 - 90%  and t(1;13)(p36;q14):  PAX7::FOXO1  in 10 - 30% GROSS - Soft, fleshy, friable tumor with irregular margins, Gray-white cut surface with variable fibrous tissue, Areas of necrosis and hemorrhage may be present

23. ALVEOLAR RHABDOMYOSARCOMA MICROSCOPY Large clusters, nests, cords and trabeculae of primitive round cells, separated by variably thick fibrovascular septa Loss of cellular cohesion in the center forms alveolar-like, cystic and vague papillary appearance Layer of cells adheres to the periphery of the spaces and fibrous septa Multinucleated tumor giant cells with wreath-like lineup of nuclei are common Positive for Desmin, myogenin (strong & diffuse), MyoD1   &  muscle specific actin (variable)

24. EMBRYONAL RHABDOMYOSCARCOMA M ost common RMS subtype, Derived from the undifferentiated mesoderm and shows phenotypic and biologic features of primitive skeletal muscle Most common in children 0 - 4 years old, but can be identified at any age Most common in the head and neck region (nasal and oral cavities & orbit), paratesticular soft tissues and the genitourinary tract, Extremity involvement is less common (< 9%) GROSS - Poorly circumscribed mass, white, soft or firm, infiltrative. Botryoid variant: resembles cluster of grapes, fleshy nodular polypoid projections of variable size into lumen

25. EMBRYONAL RHABDOMYOSCARCOMA MICROSCOPY Highly cellular neoplasm, cells arranged in loose sheets & small nests. The tumor cells are small to medium-sized with scant to moderate eosinophilic cytoplasm, oval to round nuclei, and finely dispersed chromatin. Areas of myxoid stroma and rhabdomyoblastic differentiation, with tumor cells showing eccentric nuclei and abundant eosinophilic cytoplasm (Strap cells) Botryoid variant frequently shows a cambium layer: a hypercellular zone immediately beneath the epithelial surface Positive for MyoD1  or  myogenin , Desmin &   Vimentin

26. EMBRYONAL RHABDOMYOSARCOMA DIFFERENTIAL DIAGNOSIS Alveolar rhabdomyosarcoma : Diffuse and strong nuclear staining for  myogenin  and  MyoD1 ; show  PAX-FOXO1  fusion gene product in approx 85% of cases Desmoplastic small round cell tumor : Tumor nodules on serosal surfaces, strongly  keratin + and  EMA +, may be  desmin + but  w ill not display  myogenin  or  MyoD1  positivity Ewing / PNET : Another round cell tumor, often displays Homer Wright rosettes, Nuclei are far more uniform and pale, not dense and hyperchromatic;  CD99 +,  desmin -,  MyoD1 -,  myogenin -, Look for characteristic rearrangements including t(11;22) or t(12;22) Large cell lymphoma : CD45 +, B / T cell markers present,  desmin -,  myogenin -,  MyoD1 -,  muscle specific actin - Myxoid liposarcoma : Very similar background matrix that is loose and lightly basophilic, more bland histology and more uniformity when compared to ERMS

27. DESMOPLASTIC SMALL ROUND CELL TUMOR Highly aggressive malignant mesenchymal neoplasm composed of small round tumor cells associated with prominent stromal desmoplasia, polyphenotypic differentiation Usually affects children and young adults (first to fifth decades), with peak incidence in the third decade of life, with a striking male predominance, T ypically present with abdominal pain, distension, and, occasionally ascites. Recurrent t(11;22)(p13;q12) translocation leading to formation of the  EWSR1-WT1  fusion gene, which generates a chimeric protein with transcriptional regulatory activity Large tumor masses involve the abdominal cavity, pelvis, and retroperitoneum, with multiple peritoneal implants. Paratesticular and pleural presentations are rare presentations GROSS - multiple tumor nodules, Cut surface is firm and grayish white, with foci of necrosis and hemorrhage

28. DESMOPLASTIC SMALL ROUND CELL TUMOR Histologically, DSRCT is composed of tight, variably sized nests of round cells with hyperchromatic nuclei, fine chromatin, indistinct nucleoli, and scant cytoplasm, embedded in an abundant desmoplastic stroma. Occasional cases contain rhabdoid cells; spindle cell or epithelioid morphology is rare. Some nests contain central necrosis; gland or rosette formation may rarely be identified. FIGURE

29. DESMOPLASTIC SMALL ROUND CELL TUMOR By IHC, DSRCT shows a distinctive pattern of polyphenotypic differentiation, with a combination of epithelial, neural, and muscle markers. Positive stains WT1  (C terminus) Desmin  (dot-like and perinuclear cytoplasmic staining pattern) Keratin  (dot-like cytoplasmic expression is seen occasionally) Vimentin  (dot-like cytoplasmic expression is seen occasionally) GFAP , neurofilament protein,  synaptophysin ,  NSE Negative stains WT1  (N terminus) S100 Myogenin , MyoD1 and Smooth muscle actin Chromogranin

30. DESMOPLASTIC SMALL ROUND CELL TUMOR DIFFERENTIAL DIAGNOSIS Blastemal predominant Wilms tumor : Focal triphasic elements and glomeruloid bodies, WT1  positive (both the amino terminus and carboxy terminus) Ewing sarcoma : CD99 and  NKX2.2 positive, WT1  (C terminus) negative R habdomyosarcoma : Mogenin  and  MyoD1  positive, WT1  (C terminus) negative Lymphoma : Positive for  CD45 , B cell and T cell markers, WT1  (C terminus) negative Small cell carcinoma : TTF1 ,  CD56 ,  synaptophysin  and  chromogranin  positive, WT1  (C terminus) negative PROGNOSIS Despite multimodal treatment, DSRCT is associated with dismal outcomes Approximately 60 - 70% of patients die due to disease progression, usually within 3 years after diagnosis Residual macroscopic disease after resection correlates with increased risk of mortality

31. EWING SARCOMA S econd most frequent bone sarcoma in children and young adults and has a slight male predominance 80% of patients are younger than 20 years. The tumor is more common in Caucasians Ewing sarcoma predominantly affects the diaphysis or the metaphyseal-diaphyseal portion of long bones but can also affect other bones or occur in soft tissue (10%-20%) Most common translocation is t(11;22)(q24;q12), resulting in  EWSR1-FLI1  fusion (~85 - 90%) , Second most common is t(21;22)(q22;q12), resulting in  EWSR1-ERG  fusion (~5 - 10%), Rare fusions (< 1%) involve  ETV1  (7p22),  ETV4  (17q21) and  FEV  (2q35-36)  Clinically - Localized pain and swelling, Painful enlarging mass, Associated pathologic fracture sometimes present Radiographically, an ill-defined, most often osteolytic lesion is seen, frequently accompanied by permeative bone destruction, periosteal reaction, and soft-tissue extension

32. EWING SARCOMA GROSS: Gray-tan mass with infiltrative borders, Intramedullary mass with soft tissue involvement, Areas of hemorrhage and necrosis frequent MICROSCOPY : Classical - Undifferentiated uniform small round cells in sheets with round nuclei and fine chromatin. C ytoplasm is scant and contains glycogen, which can be demonstrated using periodic acid –Schiff (PAS) Atypical Ewing sarcoma - Nuclear enlargement, Irregular nuclear contours, Vesicular or coarse chromatin, Prominent nucleoli Adamantinoma like Ewing sarcoma - Nests of basaloid cells, Peripheral palisading and cording, Prominent myxoid, fibromyxoid or hyalinized stroma, Focal keratin pearl formation

33. EWING SARCOMA Ewing sarcoma of soft tissue resembles the primary bone neoplasm. Nu clei are evenly spaced and remarkably uniform with dispersed chromatin and a finely granular quality The tumor cells are distributed in broad sheets and lobules, which are frequently separated by thick fibrous septa. Occasional examples of Ewing sarcoma show neural differentiation in the form of rosettes (tumors formerly known as PNET)

34. EWING SARCOMA IHCs (Positive) NKX2.2  (high specificity) CD99  (strong, diffuse membranous expression in ~90 - 95%) FLI1  (nuclear staining with  EWSR1-FLI1  fusion, ~90%) ERG  (nuclear staining with  EWSR1-ERG  fusion) Vimentin  (80 - 90%) Cytokeratin, p63 or  p40   (diffuse in adamantinoma-like variant) NSE  (~50%) IHCs (Negative) LCA / CD45, TdT , SATB2, WT1, Desmin, Myogenin , ETV6, CIC, BCOR, NUT1, Chromogranin, S100 (~30%), Synaptophysin (~30 - 40%), NCAM (CD56)  (~30%) P rognosis (Favourable): complete pathologic response to neoadjuvant chemotherapy, small tumor size, superficial location, easily resectable P rognosis (Unfavourable): early relapse, presence of metastases, anatomic location in trunk / pelvis

35. EWING SARCOMA DIFFERENTIAL DIAGNOSIS Small cell osteosarcoma : Tumor osteoid / matrix present, SATB2  positive Mesenchymal chondrosarcoma : Areas with hyaline cartilage differentiation, Hemangiopericytoma-like vasculature Alveolar rhabdomyosarcoma : Desmin  positive, Myogenin  and  MyoD1  positive Primary bone lymphoma : CD45  positive, TdT  positive Poorly differentiated synovial sarcoma : CK  variably positive, Biphasic type has gland-like epithelial structures CIC rearranged sarcomas : CD99  patchy positive, NKX2.2  negative, ETV4  and  WT1  positive BCOR rearranged sarcomas : Round to spindle cell morphology, Variable myxoid stromal change Desmoplastic small round cell tumor : WT1  positive, CD99  negative High grade neuroendocrine carcinoma (adamantinoma-like variant) : Synaptophysin  and  chromogranin  positive, CD99  negative

36. SMALL CELL OSTEOSARCOMA Rare & aggressive variant of osteosarcoma, composed of undifferentiated small blue round cells with a variable degree of osteoid production. Bimodal, 10-25years and > 40 years, M:F = 1.5:1.0 The small cells have round-to-oval nuclei and scant cytoplasm. Osteoid production is the key to the diagnosis and is found among sheets or nests of tumor cells. It has a lacelike pattern and should be distinguished from fibrin deposits that can be seen in Ewing sarcoma CD99 can also be positive in small cell osteosarcoma, whereas FLI1 is negative and SATB2 is positive, which may help in the distinction. EWSR1 rearrangements are absent. Other positive IHCs – Vimentin, osteonectin , osteocalcin, cytokeratins . BCOR -rearranged sarcoma also displays strong SATB2 positivity and can show bone deposition; molecular analysis is required to make the distinction N onneoplastic, osteoclast-type giant cells scattered throughout the tumor characterize the giant cell–rich variant, whereas large polyhedral tumor cells are the hallmark of the epithelioid variant

37. NEUROBLASTOMA Embryonic neoplasms with proliferation of immature cells of neural crest origin Median age at presentation 23 months, peak 0-4, Slightly more common in boys (1.2:1) years SITES - adrenal gland (MC), followed by connective/subcutaneous/soft tissue, retroperitoneum, mediastinum Radiologically - Irregularly shaped, lobulated, +/- calcification / necrosis / hemorrhage, usually heterogeneous on contrast-enhanced CT Urine biochemistry for catecholamines or their metabolites (dopamine, vanillylmandelic acid, homovanillic acid) Nonspecific markers: increased ferritin, neuron-specific enolase, lactate dehydrogenase GROSS – Vary in size from < 1cm to those that completely fill the abdomen or thorax, soft and white to gray pink, circumscribed, ovoid mass to multilobated tumor More differentiated tumors have yellow tan appearance to firm consistency. With increasing size, undergo hemorrhage, necrosis, cyst formation and calcification.

38. NEUROBLASTOMA

39. NEUROBLASTOMA Small round blue cell tumor Neuroblasts Undifferentiated:  small to medium, salt and pepper chromatin, elongated shape, may contain distinct nucleoli, thin rim of cytoplasm, vague cytoplasmic borders Differentiating  (toward ganglion cells): synchronous differentiation of nucleus (enlarged, eccentric nucleus with vesicular chromatin and single prominent nucleolus) and abundant, eosinophilic / amphophilic cytoplasm May have anaplastic, pleomorphic, spindled, rhabdoid variants May form Homer-Wright pseudorosettes surrounding delicate, eosinophilic neuropil

40. NEUROBLASTOMA M itosis karyorrhexis Index (MKI) A n important component of the histologic assessment of NBs The number of cells undergoing mitosis and karyorrhexis is expressed as a percentage of 5000 cells and is assessed on high power (×400) MKI is designated as low, intermediate, or high based on counts of less than 100 (<2%), 100 to 200 (2%-4%), and more than 200 (>4%) mitotic and karyorrhectic cells The MKI, along with patient age and grade of NB, is used to assign NBs to favorable-histology and unfavorable -histology categories

41. NEUROBLASTOMA IMMUNOHISTOCHEMISTRY Positive IHCs PHOX2B (nuclear) distinguishes undifferentiated NBs from other round cell tumors like EWS, RMS, DSRCT & MB S100, SOX10 highlights schwanian stroma but neuroblast are negative NSE, Chromogranin, Synaptophysin, Secretogranins , CD56 (NCAM), CD57, protein gene product 9.5 (PGP 9.5), Neurofilament protein, Microtubules (MAP1 & MAP2), Ganglioside D2, NB84. Negative IHCs Desmin , myogenic markers ( myogenin ,  Myo-D1 ),  EMA ,  cytokeratin ,  vimentin ,  HMB45 ,  WT1 ,  CD99 ,  CD45 DIFFERENTIAL DIAGNOSIS Desmoplastic small round cell tumor Ewing's sarcoma/primitive neuroectodermal tumor (PNET) Ganglioneuroblastoma : especially nodular variant Ganglioneuroma Lymphoma Malignant rhabdoid tumor Melanoma Schwannoma / neurilemmoma  with neuroblastoma-like features

42. NEUROBLASTOMA Genetic Alterations Description Prognostic Significance MYCN amplification ~20% of cases Strongest predictor of poor outcome (rapid tumor progression) 1p36 deletion Short arm of chromosome 1 Associated with MYCN amp & high-risk disease 11q deletion Long arm of chromosome 11 Linked to poor prognosis, independent of MYCN 17q gain Gain of distal long arm Common in high-risk tumors ALK mutations Activating mutations in ALK gene (esp. familial cases) Targetable but often high-risk TERT rearrangements Telomerase gene activation Associated with immortalization of tumor cells ATRX mutation/loss Seen in older children Associated with alternative lengthening of telomeres (ALT) and poor outcomes

43. NEUROBLASTOMA SPREAD NBs can metastasize widely through both lymphatic and vascular routes (34). The most common sites of spread include the bone marrow (78%), bone (69%), lymph nodes (42%), and liver (20%), whereas pulmonary and brain metastases are uncommon SPONTANEOUS REGRESSION Spontaneous regression of NB is well documented. Resected specimens demonstrate hemorrhage and hemosiderin deposition, necrosis, fibrosis, and prominent calcifications, similar to changes seen in post therapeutic cases. The underlying causes are incompletely understood, but genetic prerequisites such an intact chromosome 1 short arm, lack of MYCN amplification, and near triploidy are thought to be key for regression

44. NEUROBLASTOMA The International Neuroblastoma Staging System (INSS) is a surgical/pathologic staging system used historically to classify neuroblastoma based on extent of disease after surgery . INSS still plays a role in prognosis , especially when combined with clinical and biologic factors. Stage Definition Prognosis Stage 1 Localized tumor, complete gross excision Excellent (survival >90%) Stage 2A Localized tumor, incomplete gross excision, negative lymph nodes Good Stage 2B Localized tumor, may or may not be completely excised, positive ipsilateral lymph nodes Good to Intermediate Stage 3 Unresectable tumor crossing midline or bilateral lymph nodes Intermediate to Poor , depending on age, histology Stage 4 Distant metastasis (e.g., bone, bone marrow, liver) Poor (especially in children >18 months) Stage 4S <1-year-old with localized tumor and limited metastasis (skin, liver, marrow) Favourable , may spontaneously regress

45. NEUROBLASTOMA

46. WILMS TUMOR (NEPHROBLASTOMA) Wilms Tumor is a triphasic embryonal tumor of the kidney arising from persistent nephrogenic rests (remnants of immature kidney tissue) composed of varying proportions of: Blastemal (small round blue cells) Epithelial (forming tubules and glomeruloid structures) Stromal (mesenchymal, which may differentiate into muscle, cartilage, or fat) Peak incidence between the ages of 2 and 5 years, with 90% being diagnosed by age 6 years , s light female preponderance Usually presents as abdominal mass , o ther signs or symptoms (present in 20 - 30% of cases): Abdominal pain, Hematuria , Hypertension , Anemia

47. WILMS TUMOR (NEPHROBLASTOMA) WT typically presents as a unicentric, spherical mass that is sharply demarcated from renal parenchyma. Approximately 10% are multicentric, Bilateral tumors are present in 5% to 6% of cases Cut surface is usually pale gray and uniform, but focal hemorrhage, necrosis, and cyst formation are commonly encountered. The texture is usually soft and friable Prominent septa often impart a nodular appearance WT can arise anywhere in the cortex or medulla, usually compressing and distorting renal parenchyma around its margin

48. WILMS TUMOR (NEPHROBLASTOMA) Composed of variable amount of blastemal, epithelial and stromal components, may show 2 or only 1 component Blastemal S mall to medium sized undifferentiated cells with small regular nuclei and nucleoli Least differentiated component May show different patterns (diffuse, serpentine, nodular and basaloid patterns) Mitotic figures frequent