BY – Dr. KANWALPREET KAUR

MODERATOR-Dr. KARUNA GUPTA

Heterogeneous group of neoplasms are characterised

by the sheets of poorly differentiated cells:

• Small (similar to lymphocyte in size)

• Round (round nuclei and scanty cytoplasm)

• Blue (blue staining due to high nuclear/cytoplasmic

ratios

• Ewings sarcoma/Primitive neuroectodermal tumour(ES/PNET

• Hematopoietic malignancies

• Plasma cell neoplasms

• Small cell osteosarcoma

• Mesenchymal chondrosarcoma

• Poorly differentiated small cell synovial sarcoma

• Rhabdomyosarcoma(embryonal and alveolar subtypes)

• Histological grading of bone sarcomas is an attempt to

predict the biological behaviour of a malignant tumour

• Criteria used—

1. Cellularity i.e., the relative amount of cells compared to

matrix

2.Nuclear features of the tumour cells

• Tumours which are monomorphic, such as small cell

malignancies (Ewing sarcoma, malignant lymphoma and

myeloma), do not lend themselves to histological grading.

• Mesenchymal chondrosarcomas and dedifferentiated

chondrosarcomas are always high grade

• Round cell sarcomas that show varying degrees of

neuroectodermal differentiation

Ewing’s sarcoma - limited neural differentiation

PNET - more neural features

• AGE- 5-20 years (commonly)

• infancy or adulthood rarely

• SEX PREDILITION- males:females=1.4:1

OSTEOLYTIC

LESION

LAMELLATED

PERIOSTEAL

REACTION

SUNBURST

PERIOSTEAL

REACTION

• Generally arises in

medullary cavity of

shaft from which it

permeates cortex and

invades soft tissue

• Rarely, periosteal

• Soft, tan-white, areas of

haemorrhage and

necrosis

1. Classic or conventional (typical) Ewing sarcoma

2. Primitive neuroectodermal tumor(PNET)

3. Atypical Ewing sarcoma

• Same immunohistochemical and molecular features,

differing only in the extent of neural differentiation.

• Each subtype is considered a high-grade tumor.

sheets of uniform

population of cells;

round nuclei ; finely

granular chromatin;

indistinct cell borders;

necrosis common;

mitotic activity usually

not prominent

Homer- wright rosette

3. ATYPICAL-most difficult group to recognize

• Great degree of cytologic variability and/or unusual growth

patterns e.g. large nuclei with irregular nuclear membranes

and prominent nucleoli; abundant eosinophilic cytoplasm

imparting a rhabdoid appearance.

The cells of ES/PNET usually

contain large amounts of

cytoplasmic glycogen, as

demonstrated by a PAS stain

with diastase control

Non reactive for chromogranin, glial fibrillary protein, desmin, muscle

specific actin, myogenin and CD45. Keratin is positive in 20% to 30% of

cases, usually with a focal distribution.

CD 99 reactivity FLI-1 Protein expression

• CD99- strong, diffuse membranous staining pattern

• 84-100% sensitive. If a tumor is negative for

CD99, it is highly unlikely to be Ewing sarcoma

• NOT A SPECIFIC MARKER

• Can be seen in RMS, glial tumours, neuroendocrine

tumours, lymphoblastic lymphoma, WT, clear cell

sarcoma of kidney, teratoma, synovial sarcoma,

osteosarcoma and mesenchymal chondrosarcoma

• CD99 is important for distinction between Ewings

sarcoma/PNET and metastatic neuroblastoma

• FLI1- Only nuclear staining is considered positive

NOT SPECIFIC MARKER

But also positive in lymphoblastic lymphoma,

myeloid neoplasms, DSRCT, Malignant melanoma, merkel

cell carcinoma,synovial sarcoma, and some vascular

neoplasms.

• Reciprocal translocation t(11;22)(q24;q12)

• Fusion of EWSR1 gene(encodes for RNA binding protein) at 22q12 with FLI1 gene(member of ETS family of transcription factors)

• The t(21;22)(q12;q12) translocation involves the gene ERG, which is located on chromosome 21

• t(7;22)(p22;q12) translocation involves a gene known as ETV1 at 7p22.

• Recently a translocation involving chromosomes 4 and 9 with CIC and DUX4 gene has been identified

• Rearrangements of EWSR1 with non–ETS-family

genes—including NFATC2,POU5F1, SMARCA5, ZSG,

and SP3—are also rarely identified

• FISH for EWSR1 genomic rearrangements

is highly sensitive (>95%) but nonspecific because

other tumours may show rearrangement of this locus.

• RT-PCR for EWSR1 fusion genes - highly sensitive

(>95%) and specific (100%).

• Primary Lymphoma- Originates in bone with no evidence of extraskeletal disease or disseminated bone marrow

involvement. Rare

• Secondary skeletal involvement by a primary extraosseouslymphoma is much more common than primary bone lymphoma

• AGE-usually affects 40-60 years

• Lymphoma however can involve children; though it is much less common than Ewing sarcoma in this age group

• SITE- meta-diaphyses of long bones (femur, humerus, and tibia) and axial skeleton (pelvis and vertebrae)

Extensive involment with permeative

destructive process.

Shaft is usually involved

Radiographs appear as if there are

multiple small holes with intervening

normal bone

Lesion shows mixture of lysis and

sclerosis

Periosteal new bone formation is

unusual

Bone scan- positive

Positive bone scan or lesion on MRI + normal radiograhs = suggest malignant lymphoma

->Under low power, lesion is

visible between normal bony

trabeculae and in marrow fat

->Nodular growth pattern-

distinctly uncommon

->Fine fibrosis may be evident

->Most lymphomas show

polymorphic infiltrate

->Nuclei are not uniform in

shape and size

This lack of uniformity is

helpful in distinguishing

lymphoma from Ewings

sarcoma of bone

• B-cell lymphomas, most commonly diffuse large B-cell

lymphoma

• T-cell lymphomas of bone-Anaplastic large cell

lymphoma

• Lymphoblastic lymphoma

• Non-Hodgkin B-cell lymphomas, including follicular

lymphoma, marginal zone lymphoma, mantle cell

lymphoma, and small lymphocytic lymphoma

• Hodgkin lymphoma- late stages

• Myeloid sarcoma (granulocytic sarcoma)

TUMOUR MARKERS

B-cell lymphomas CD45,

pan B-cell markers (CD19, CD20,

CD79a,PAX-5)

Negative for CD3, CD5

Anaplastic large cell lymphoma CD30 ,CD3, CD4,

Lymphoblastic lymphoma terminal deoxynucleotidyl transferase.

CD10, CD43, CD99, FLI-1,

CD45 - weakly positive or negative

Hodgkin’s lymphoma CD30, PAX-5, CD15.

Myeloid sarcoma (granulocytic

sarcoma)

Positive- myeloperoxidase, lysozyme, and

CD43,CD45

Negative for CD20 and CD3

Most of lymphomas except lymphoblastic lymphoma are negative for CD99

• Lymphoblastic lymphoma may be positive for CD99 and

negative for CD45, an immunoprofile that overlaps with

that of Ewing sarcoma

• TdT, CD34,CD43,CD10, CD79a and genetic

rearrangement studies- distinguish lymphoblastic

lymphoma from EWS/PNET

• Specific studies on primary lymphomas of bone are

lacking.

• malignant proliferation of monoclonal plasma cells

• can present as a solitary lesions (solitary plasmacytoma)

or more commonly as part of widespread disease

(multiple myeloma)

• AGE-50-70years

• rare below 40 years

• SITE-: vertebrae, ribs, skull, pelvis, femur, clavicle and

scapula

Multiple punched out lesions

Purely lytic

Rarely associated with sclerosis

Purely lytic lesion;

Well defined margins

• Usually has a soft red-brown appearance.

• However, some myelomas show the fish-flesh

appearance typical of malignant lymphoma.

WELL DIFFERNTIATED MYELOMA

.

POORLY DIFFERNTIATED MYELOMA

• HISTOLOGICAL DIFFERENTIAL DIAGNOSIS

INCLUDES:

• 1.Lymphoma

• 2.malignant carcinoma

• 3.occasionally chronic osteomyelitis

• Immunohistochemitry plays an important role here

• Myeloma cells positive- CD38

CD138

Multiple myeloma oncogene 1 (MUM-1)

• Characteristically express monotypic cytoplasmic Ig and lacks

surface Ig

• The monotypic expression of kappa or lambda

immunoglobulin by the tumour cells establishes the diagnosis

of malignancy

• Myeloma cells negative CD19,CD20,CD27,CD22

Normal plasma cells CD 27+ , CD 19+

• Myeloma cells frequently express the natural killer

antigen CD56/58 which is not expressed in reactive

plasma cells

• Myeloma cells weakly positive or negative for CD45,CD20

most B-cell lymphomas strong staining for both markers.

• Both myeloma and carcinoma are positive for EMA

Keratin markers are more reliable in ruling out carcinoma

• Myeloma cells positive for CD138

Multiple myeloma oncogene 1 (MUM-1)

Some carcinomas occasionally express CD138

MUM-1 is helpful in making distinction

• Aggressive cartilaginous neoplasm

• AGE-20-60 year

• BONES COMMONLY AFFECTED- jaw bones

• ribs

• vertebrae

• pelvis

• USUAL LOCATION WITHIN LONG BONE- diaphysis

(cortex or medulla)

Hemangiopericytomatous patternmalignant cartilaginous nodule ;

hypercellular region of small cells

• Vimentin

• S-100 protein staining- limited to chondroblastic islands.

lacking in small cell component

• CD57

• CD99- limited to small cell component

• Nuclear immunoreactivity – Sox9 and osteocalcin

• Focal reactivity for actin,desmin,myogenin,NSE

MOLECULAR GENETICS• HEY1–NCOA2 gene fusion

• complex cytogenetic alterations, including identical Robertsoniantranslocation t(13;21)(q10;q10)

• Hematopoietic stains will rule out lymphoma

• Both mesenchymal chondrosarcoma and Ewings

sarcoma/PNET share immunoreactivity for CD99

FLI-1-positive in 75% cases of Ewings sarcoma

Sox9- sensitive and specific marker for mesenchymal

chondrosarcoma

• Osteosarcoma is the most common nonhematopoietic

primary malignant bone tumor.

• But small cell osteosarcoma ( histological variant) is an extremely uncommon tumor with a poor prognosis

• AGE- 10-25 years ; rare in preschool children

• another peak age incidence- after 40

• SEX- M:F=3:2

• SITE- metaphyseal area of long bones

• lower end of femur

• upper end of tibia

• upper end of humerus

• Small cell osteosarcoma is a rare histological variant

• MICROSCOPY- Small size and uniformity of tumour cells

and diffuse pattern of growth is seen – simulating

appearance of Ewing sarcoma/PNET and malignant

lymphoma

• Some cases- these cells are spindle rather than round

• Focal production of osteoid – distinguishing feature

• Areas of cartilage production can be seen

• Difficult to distinguish small cell osteosarcoma from

ewings sarcoma/PNET when osteoid is not present

• IMMUNOHISTOCHEMISTRY-

• No specific immunophenotype for osteosarcoma

• Immunohistochemically heterogenous

• Positive for vimentin,

• desmin,

• smooth muscle actin,

cytokeratin

epithelial membrane antigen,

S-100

type I collagen, type II collagen, type IV collagen

proteins associated with bone metabolism like-

osteonectin,osteocalcin, osteopontin.

CD 99

• Hematopoietic immunostains will distinguish lymphoma

from small cell osteosarcoma

• Small cell osteosarcoma can be immunoreactive with

CD99, so it is not a useful stain in ruling out Ewing

sarcoma

FLI-1 is a better marker

most Ewing sarcomas are positive

but small cell osteosarcomas are negative.

• The stromal component of small cell osteosarcoma may

resemble mesenchymal chondrosarcoma.

both can show reactivity to CD99

- Careful attention paid to the type of matrix production—

osteoid in osteosarcoma and

cartilage in mesenchymal chondrosarcoma

is the best way to make the distinction

• Small cell variant of poorly differentiated synovial

sarcoma is easily misdiagnosed for other small round cell

tumours

• IMMUNOCHEMISTRY- positive for keratin 7,13 and 19

EMA, vimentin , CD99

• MOLECULAR GENETICS- t(x;18)(p11.2;q11.2)

fusion of SS18( chr 18) with SSX1 (chr X)

• Only two categories show small round cell picture on

histology:

1.Embryonal rhabdomyosarcoma

2.Alveolar rhabdomyosarcoma

EMBRYONAL RHABDOMYOSARCOMA • Arises from unsegmented and undifferientiated mesoderm

• SITE- head and neck region- orbit, nasopharynx, middle ear

retroperitoneum

bile ducts

urogenital tract

• AGE- 3-12 years

• GROSS- poorly circumscribed, white, soft

ALVEOLAR RHABDOMYOSARCOMA• AGE- 10- 25 years

• SITE- Extremities- forearm,arms, perirectal, perineal regions

Most common sites of metastatic involvement bone marrow, lungs, soft tissues, lymph nodes

Perivascular pseudorosette

Small round cells

Spindle shaped

cells;Nuclei oval;

cytoplasm scanty &

eosinophilic

Small round cells

Connective tissue septa

IMMUNOHISTOGRAM OF RHABDOMYOSARCOMA

Embryonal rhabdomyosarcomaAlveolar rhabdomyosarcoma

ALVEOLAR RHABDOMYOSARCOMA:

• t(2;13)(q35;q14) with PAX3/FOXO1A fusion

• t(1;13)(p36;q14) with PAX7/FOXO1A fusion(FOXO1A was previously known as FKHR)

Detected in paraffin embedded tissue with FISH technique

EMBRYONAL RHABDOMYOSARCOMA

• No distinctive genetic alterations

• Loss of heterozygosity at 11p15.5

• Gain of chromosomes 2,8,13

Thank you…