Soft Tissue Sarcoma

Question 1

What are key features of soft tissue tumours?

Answer 1

Many have uncertain lineage

Arise from genetic changes rather than differentiated cells i.e. leads to tumours arise in area of cells completely different to tumour cell type

Associated with molecular abnormalities

Question 2

What molecular abnormalities can give rise to soft tissue tumours?

Answer 2

Translocations
-new oncogenic fusion genes formed

Somatic mutations

Copy number abnormalities i.e. gene amplification or deletion

Complex unbalanced karyotypes

Question 3

What broad categories of soft tisse tumour are there?

Answer 3

Apipocytic = fat-forming

• lipoma
• liposarcoma

Smooth muscle tumours

• leiomyoma
• leiomysarcoma

Nerve sheath tumours

• Schwannoma
• Malignant peripheral nerve sheath tumour

Vascular

• angiosarcoma
• kaposi sarcoma

Small round cell tumours

• Ewing sarcoma
• rhabdomyosarcoma

Question 4

What is a lipoma?

What are key characteristics of this tumour?

Answer 4

Most common form of soft tissue tumour which can occur at any site

Resembles normal fat
Grows slowly
Benign

Question 5

What is a liposarcoma?
Where does it most commonly occur?
How do they tend to affect?
What are the different types of liposarcoma?

Answer 5

Malignany fat-forming tumour and is most common soft tissue sarcoma

Peak age= 60-70 (WDL) and 20-60 for myxoid

Lower extremitites and retroperitoneum (patients can just think they’re putting on weight)

Well-differentiated liposarcoma (WDL)

• tumour cells resemble fat cells
• amplification leads to increased proliferation

De-differentiated liposarcoma (DDL)
-pleomorphic

Myxoid
-tumour resembles embyronic fat i.e. lipoblasts

Question 6

What is a leiomyoma?
Where does it commonly occur and how would it present?
What is it treated?

Answer 6

Benign smooth muscle tumour

Uterus as fibroids
Extra-uterine soft tissue
Large lesions cause pain and bleeding

Excision is curative

Question 7

What is a leiomyosarcoma?
Where does it commonly occur?
What factors can pre-dispose?

Answer 7

Malignant smooth muscle tumour

Uterus
Extra-uterine= limbs/retroperitoneum/large vessels
I.e. can grow in wall of veins and lead to venous occlusion

Oestrogen
Irradiation
Immune suppression i.e. EBV

Question 8

What is a schwannoma?
Where does it occur?
When might a patient experience pain with this tumours?
What is the treatment?

Answer 8

Benign tumour of Schwann cells of the nerve sheath

Effects peripheral nerves

Pain when inpinges the nerve

Surgical excision of solitary lesions

Question 9

What are the features of malignant peripheral nerve sheath tumours?

Answer 9

50% of them occur in neurofibromatosis type 1

Very rarely associated with schwannoma

Can present with mass with pain or parathesia due to nerve association

Can metastasise

Question 10

What is an angiosarcoma?

When does it typically occur?

Answer 10

Aggressive vascular tumour which can present as haemorrhagic tumours infiltrating into SC

Develops on skin of elderly person due to increased sun exposure

Question 11

What is a specific subtype of angiosarcoma?

Who develops this tumour?

Answer 11

Kaposi sarcoma
-locally destructive tumour of blood vessels

All cases associated with HHV-8
Commonly occurs in immunosuppresed patients

Question 12

What are the aims of soft tissue tumour diagnosis?

Answer 12

Identify differentiation i.e. lineage

Predict the behaviour and malginant potential of tumour

Guide treatment

Assess progression

Question 13

How do soft tissue tumours classically present?

Answer 13

Mass- can be painful or painless

Can cause parathesia or obstruction

Might have FH

Might have PMH of trauma/previous disease or therapy

Question 14

Which soft tissue tumours are associated with childhood?

Answer 14

Neuroblastoma

Embyronal rhabdomyosarcoma

ALL

Question 15

Which soft tissue tumours are associated with adulthood?

Answer 15

Small cell carcinoma

Small cell melanoma

Alveolar rhabdomyosarcoma

Ewing Sarcoma

Roud cell liposarcoma

Poorly differentiated synovial sarcoma

Endometrial stromal sarcoma

Question 16

How is the depth of STT associated with progrnosis?

What is of increased likelihood if lesion is below deep fascia?

Answer 16

Benign= tend to be superficial

Most superficial= better staging i.e. related to prognosis

Increased likelihood of sarcoma

Question 17

What are the different methods of biopsying a STT?

What are samples placed in once collected and why?

Answer 17

FNAC
Core biopsy
Excision

Placed in fixative:

• prevents decay
• stabilizes tissue

Question 18

Asside from biopsy what other methods are used to identify the type of tissue sample?

Answer 18

Immunohistochemistry
-antibodies bind to specific antigens

FISH

• look for gene rearrangements
• amplification

Reverse transcription PCR

• fusion transcripts
• mutational anaylsis

Question 19

What are the potential problems with FISH?

Answer 19

It is sensitive but not specific because the genes can partner with multiple others when fusing

Question 20

What are the potential problems with RT-PCR?

Answer 20

Specific but cannot detect uncommon fusions

There can be problems with RNA extraction

Question 21

What are prognostic factors for STT?

Answer 21

Age 
Site 
Size 
Grade-> degree of differentiation 
Stage-> degree of spread 
Proliferation markers 
Differentiation markers

Question 22

What grading system is used for STT?

Answer 22

French federation of cancer centres grading system

• Differentiation score
• mitotic count
• necrosis