Soft Tissue tumors

Question 1

The majority of soft tissue tumors are due to what?

Answer 1

Most cases are unknown cause.

Documented causes can be: radiation, chemical burns, thermal burns, trauma

Majority are sporadic!

Question 2

Genetic conditions linked to soft tissue tumors?

Answer 2

Li-Fraumeni
Neurofibromatosis Type 1
Gardner Syndrome
Osler-Weber Rendu Syndrome

Question 3

Where are the majority of soft tissue tumors?

Answer 3

In the lower extremities, particularly the thigh.

Question 4

Most common sarcoma in children?

Answer 4

Rhabdomyosarcoma

Question 5

Most common sarcoma in young adulthood?

Answer 5

Synovial sarcoma

Question 6

Most common sarcoma in adulthood?

Answer 6

Lipsarcomas, but also pleomorphic or undifferentiated sarcomas

Question 7

How is degree of differentiation assigned?

Answer 7

I = Well Differentiated (good prognosis)
II = Moderately Differentiated
III = Poorly Differentiated (bad prognosis)

Question 8

What goes into grading I-III

Answer 8

Differentiation level (usually the biggest factor, I-III).
Extent of necrosis, which is a correlate for rate of growth
Number of mitoses on average per high-power field

Other important factors are size (>5 cm is dangerous), depth (above or under fascia… under fascia has higher risk for invasiveness), and stage (I-IV, which is a clincal assessment)

Deep lesions are more dangerous than superficial locations such as skin, in GENERAL

Grade is I-III

Question 9

Lipoma characteristics

Answer 9

1. Common in adulthood.
2. Most commonly solitary lesions.
3. If multiple are present, it usually indicates an underlying genetic condition.
4. Generally mobile, slowly enlarging, and painless masses
5. Complete excision is generally curative

Note: Angiolipomas can manifest with local pain

Question 10

Conventional Lipomas are generally…

Answer 10

Soft, yellow, well-encapsulated masses, consisting of mature white fat cells with NO pleomorphism

Question 11

Liposarcomas affect what age group?

Answer 11

40-60s

Question 12

Where are liposarcomas usually?

Answer 12

Proximal extremities, retroperitoneum… may develop into large tumors

Many variants (well differentiated, myxoid/round cell, pleomorphic histological variants)

Question 13

WD-LPS

Answer 13

Well differentiated liposarcomas are generally indolent.

Myxoid/round cell type is intermediate

If pleomorphic, it can be aggressive and metastasize, which is why early excision is required to prevent this from occurring.

Have lipoblasts on histology

Question 14

What is a lipoblast

Answer 14

An adipocyte that is now resembling a fetal fat cell, with an indented nucleus and multiple small fat vacuoles. This is CLASS in WD-LPS!!

Question 15

What chromosomal issues are responsible for WD-LPS?

Answer 15

Amplication of 12q14-q15…. Contains MDM2

Question 16

What chromosomal issues cause Myxoid/RoundLPS?

Answer 16

t(12-16)(q13;p11)

Question 17

Nodular fasciitis

Answer 17

affects the deep dermis, subcutis, or muscle

Several centimeters with poorly defined margins.

Resembles a tumor, grows rapidly and causes local damage, but it is not a malignancy! Will have many mitotic figures and look like sarcoma

A post-traumatic proliferation that resembles sarcoma

Question 18

Myositis Ossificans

Answer 18

Affects proximal extremitis, young adults, trauma in >50% of cases

Has metaplastic bone; eventually the entire lesion ossifies and the intertrabecular spaces are filled with marrow.

Must be distinguished from osteosarcoma… it is also a post-traumatic proliferation

Question 19

Where do Fibromatoses stand on the spectrum of malignancy and what tissues do they commonly affect

Answer 19

Lie between low grade sarcoma and aggressively benign tumors. Can do a lot of local damage, but will not metastasis… superficial ones can be penile, plantar, palmer

Often times they spontaneously resolve

Question 20

Deep-Seated Fibromatosis (aka Desmoid Tumors) Characteristics

Answer 20

These are more aggressive than superficial fibromatoses…Frequently recur after incomplete excision, more of like a low grade sarcoma but sometimes like an aggressively benign tumor

Occur in young adulthood to 30s

Associated with Gardner syndrome

Due to mutations in APC or beta-catenin

Question 21

Fibrosarcoma

Answer 21

These are malignant, unlike fibromatosis

Composed of fibroblasts

Occur in adulthood

Occur in deep tissues… thigh, knee, retroperitoneum

Aggressive. Recur in most cases… A quarter will metastasize

Negative for all markers but VIMENTIN. VIMENTIN IS A MARKER FOR MESENCHYMAL ORIGIN

Question 22

Uterine Leiomyomas

Answer 22

Most common neoplasm in women. Also known as uterine fibroids.

Question 23

Smooth muscle tumor characteristics

Answer 23

May arise deeply or superficially

Usually < 1-2 cm

Solitary lesions can be cured easily, but multiple tumors are difficult to treat

Question 24

Leiomyosarcoma

Answer 24

More common in females than males, and generally present in adult. It is much more pleomorphic than a leiomyoma.

Affect deep and superficial soft tissues of extremities and retroperitoneum.

Superficial leiomyosarcomas have good prognosis, but in the retroperitoneum they can be large and cannot be full excised, and often times will spread

Question 25

Rhabdomyosarcoma

Answer 25

Most common sarcoma of childhood and early adolesence, usually occurs before age 20

Most commonly in areas with normally very little skeletal muscle, such as the head/neck or GU

Three subtypes

1. Embryonal
2. Alveolar
3. Pleomorphic

Question 26

Embryonal RMS

Answer 26

Half of all rhabdomyosarcomas
Most common before the age of ten
Occurs in Head & NEck, in orbit and near meninges, but also in GU

Sometimes occurs in pelvis, retroperitoneum and other deep soft tissues

May be anaplastic. Contain characteristic tadpole cells on histology

Stain for desmin, a marker for muscle differentiation… also stain for MyoD1 and Myogenin, which are unique for skeletal muscle

Question 27

Alevolar RMS

Answer 27

Around a third of rhabdomyosarcoma

Occurs from 10-25 years of age, a bit older than embryonal.

Deep soft tissues of extremitis. Not as common in Head and neck, pelvis, peritoneum or retroperitoeum.

More aggressive than embryonic RMS.

Histology looks very big thick cells separated by large fibrous layers

Question 28

What mutation is common in 80-85% of Alveolar RMS?

Answer 28

t(2;13)/PAX3-FKHR or t(1;13)/PAX7-FKHR

Question 29

Synovial sarcoma

Answer 29

More common in males, young adults.

Unknown histogenesis, but occurs in deep soft tissues of extremities… Generally the KNEE

It is X linked translocation.. t(X;18)(p11;q11)

Histologically can be biphasic or mono phasic… Sometimes glandular formations will also be visible.

Treat with aggressive limb-sparing surgery and chemo

Common metastatic sites are lung, bone, and regional lymph nodes

5 year survival is poor. (25%-60%)

The name is a misnomer… it seeds the synovium, but the primary origin is UNKNOWN