General Soft tissue

Question 1

What are the most common soft tissue sarcomas of adults?

Answer 1

Undifferentiated pleomorphic sarcoma formerly aka malignant fibrous histiocytoma and liposarcoma.

Question 2

What are the most frequent soft tissue sarcomas of childhood?

Answer 2

Rhabdomyosarcoma, neuroblastoma, and Ewing sarcoma.

Question 3

Common peripheral histologic subtype of soft tissue sarcomas.

Answer 3

undifferentiated pleomorphic sarcoma, liposarcoma, synovial sarcoma

Question 4

Common retroperitoneal sarcoma.

Answer 4

leiomyosarcoma and liposarcoma

Question 5

Common head and neck sarcoma

Answer 5

hemangiopericytoma, rhabdomyosarcoma, UPS

Question 6

Common thoracic sarcoma

Answer 6

UPS, angiosarc, synovial

Question 7

common visceral sarcoma

Answer 7

angiosarc, UPS, leiomyosarc/GIST

Question 8

keratin positive soft tissue tumours

Answer 8

normal mesenchymal cells (except endothelial cells) has limited expression of keratins.

epithelioid sarcoma
Epithelioid hemangioendothelioma
epithelioid angiosarcoma
extrarenal malignant rhabdoid tumour
synovial sarcoma
leiomyosarcoma
schwannoma (retroperitoneal)
inflammatory myofibroblastic tumour
pseudomyogenic hemangioendothelioma
desmoplastic small round cell tumour
alveolar rhabdomyosarcoma
ewing sarcoma

Question 9

What is desmin?

Answer 9

intermediate filament of muscle cells, expressed in benign and malignant tumours of smooth and skeletal muscle, and myofibroblastic tumours, and non-myogenic tumours eg desmoplastic small round cell tumours, and angiomatoid fibrous histiocytoma.

Question 10

What is GFAP? What is its role in diagnosis of soft tissue tumours?

Answer 10

glial fibrillary acidic protein is a major structural component of astrocytes. Expressed in schwann cells of peripheral nerves and myoepithelial cells. Diagnostic application in peripheral nerve sheath tumours and myoepithelial tumours, highlight asons in benign peripheral nerve sheath tumours.

Question 11

Name myogenic markers used in diagnosing soft tissue tumours.

Answer 11

SMA - smooth muscle actin
h-caldesmon - smooth muscle
myogenin - skeletal muscle specific

Question 12

Name some endothelial markers
What tumours express these?

Answer 12

CD34 - solitary fibrous tumour, DFSP, spindle cell lipoma, GIST, epithelioid sarcomas, MPNST.

CD31 - more sensitive and specific than CD34, macrosphages, and histiocytic sarcoma

Factor VIII related antigen - less sensitive , lots of background staining, and abandoned for more reproducible diagnostic.

FLI1 (common fusion partner in Ewing sarcomas), also positive in lymphocytes and other mesenchymal and non-mesenchymal tumours

ERG - most sensitive and specific endothelial marker available but not very specific, prostatic adenoCa (those with TMPRSS2-ERG fusion), Ewing (EWSR1-ERG fusion), some acute myeloid leukemias.

Question 13

Name a lymphatic marker, what tumour does it mark? Why is it not used for diagnosis of vascular tumours?

Answer 13

Podoplanin is recognised by D2-40 monoclonal antibody. Kaposi and some angiosarc, epithelioid hemangioendotheliomas

Podoplanin is not specific for endothelial differentiation, and is expressed in mesothelioma, seminomas, follicular dendritidc cell sarcomas.

Question 14

Name a schwannian marker

Answer 14

S100, GFAP, sox10, cd56, CD57

Question 15

What is EMA?

Answer 15

Epithelial membrane antigen, MUC1 is a transmembrane mucin widely expressed in epithelial cells, marker for carcinoma. Use in soft tissue tumours is limited. EMA is expressed in plasma cell neoplasms, and anaplastic large-cell lymphoma

Question 16

What is CD99 used for?

Answer 16

cell surface glycoprotein normally expressed on thymic T lymphocytes, positive in lymphoblastic lymphomas. Ewings sarcomas, strong membranous staining patterns. CIC-DUX4 sarcomas may be positive for CD99.

Question 17

IHC for fibromatosis

Answer 17

β-catenin (+) (nuclear), especially in deep lesions, SMA(+); desmin (-), keratins (-), CD117(+/-)

Question 18

how do you distinguish Granuloma annulare and Rheumatoid nodule?

Answer 18

Rheumatoid nodule - Palisading histiocytes around central fibrin

Granuloma annulare - Central mucin with surrounding palisade of histiocyte

Question 19

IHC for clear cell carcinoma of gynae tract

Answer 19

CK7, EMA, pax-8, HNF-1-β, napsin-A, racemase usually strongly and diffusely positive

ER, PR frequently negative

OCT4 may be focally positive

AFP and glypican-3 may be positive, SALL4 negative

p16 strong positivity in ~ 20%

WT1 negative

p53 wild-type expression common (~ 25% strong and diffuse positivity)

BAF250a (ARID1A) loss of expression common

Subset with MMR loss

SMARCA4 loss rare

Genetic Testing

ARID1A (~ 50%) > PIK3CA (40%) > PTEN ( < 10%) mutations

MET, ARID1B, PIK3R1, SMARCA4, and SMARCD3 rare

Question 20

IHC for serous, endometrioid, and clear cell carcinoma.

Answer 20