18 - Soft tissue tumors Flashcards
What does the embryonic mesoderm give rise to?
Skeletal system, muscular system (smooth and skeletal), dermis and connective tissue.
Hematopoietic systenm reproductive system, plaura and peritoneum, and the adrenal cortex.
What are mesenchymal (soft tissue) tumors? How are they classified?
Nonepitheilal extraskeletal tumors (excluding reticuloendothelial system, glia, and supporting tissue of parenchymal organs).
Classified according to the tissue they recapitulate such as muscle, fat, fibrous tissue, vessels, or nerves.
Malignant soft tissue tumors use the suffix ______.
Sarcoma
What is the incidence of sarcomas? What percentage are soft tissue vs bone?
1% of all cancers, ~12,000 cases/yr in the US.
- 75% soft tissue
- 25% bone
Are there more benign soft tissue tumors or sarcomas?
Benign soft tissue tumors outnumber sarcomas 100:1.
Mostly lipomas and hemangiomas.
What is the pathogenesis of soft tissue tumors? Give examples. (This is important)
Most occur sporadaically, but an important minority are associated with a genetic syndrome.
- Neurofibromatosis type 1: (malignant periferal nerve sheatch tumor), NF1 mutation
- GArdner syndrome (fibromatosis), APC
- Li-Fraumeni syndrome (soft tissue sarcoma), P53
- Hereditary hemorrhagic talangiectasia (Osler-Weber-Rendu syndrome), multiple genes.
The cause of most soft tissues is ______. What are some associations?
Unknown.
Documented association following radiation, rare instances from chemical burns, thermal burns, or trauma.
Cytogenetic and molecular analyses of tumors can give significant insight into their biology.
What is the age distribution associated with sarcoma?
Overall incidence increases with age (15% arise in children).
Certain sarcomas apepar in certain age groups:
- Rhabdomyosarcoma in young adulthood
- Synovial sarcoma in young adulthood
- Liposarcoma and pleomorphic or undifferentiated sarcomas in later adult life
What is the anatomic distribution of sarcomas?
Can occur in any location.
60% occur in extremeties, 40% in lower extremities (esp the thigh).
What are some things needed for diagnosis of sarcomas? What techniques can be used?
Histologic classification: cell morphology and architectural arrangement.
These may not distinguish one sarcoma from another (particularly with poorly differentiated tumors).
Ancillary techniques are helpful: immunohistochem., EM, cytogenetics, and molecular genetics.
The ____ of a soft tissue sarcoma is an important factor for predicting its behavior. How does this work?
The grade
Usually I to III (low/intermediate/high) is based largely on:
- Degree of differntiation/pleomorphism
- Avg # of mitosis per high power field
- Extent of necrosis (presumably a reflection of rate of growth)
Other than grade, what other factors also provide important diagnostis and prognostic information? In general, what tumors tend to have better prognoses?
Size (> or <5cm), depth (above or under fascia), and stage (I-IV).
In general, tumors arising in superficial locations (skin and subcutis) have better prognosis than deep lesions.
How do you treat sarcomas?
Soft tissue sarcomas are usually treated with wide surgical excision (freq. limb sparing)
Radiation and chemo are used for large and/or high-grade tumors.
What are the 6 types of soft tissue tumors? Give examples of each.
- Adipose tissue: lipoma, hibernoma, liposarcoma
- Nerve: neurofibroma, schwannoma, perineurioma
- Muscle: leiomyoma, leiomyosarcoma
- Fibrous tissue: fibroma, fibromatosis, fibrosarcoma
- Blood vessels: hemangioma, hemangioendothelioma
- Misc.: myositis ossificns, angiofibroma, synovial sarcoma.
What is the most common soft tissue tumor of adulthood? What is their behavior? How can they be treated?
Lipoma: benign tumoe of adipose tissue
- most are solitary lesions - multiple lipomas suggest the presence of rare hereditary syndromes
- Msot are mobile, slowly enlarging, painless masses (angiolipomas may cause local pain)
- Complete excision is usually curative
How are lipomas classified?
According to particular morphologic features (angiolipoma, spindle cell lipoma)
How do lipomas appear grossly and on histology?
Conventional lipomas (most common subtype) are soft, yellow, well-encapsulated masses.
On histology, they consist of mature white fat cells with no pleomorphism.
What is the genetic abberation seen in conventional lipomas?
12q14 - q15
What is a liposarcoma? What do they look like on histology and where do they often occur in the body?
One of the most common sarcomas of adulthood (40-60)
- Deep soft tissues of proximal extremeties and retroperitoneum.
- May develop into large tumors
- Well-differentiated, myxoid/round cell, and pleomorphic variants.
Pic: well-differentitated liposarcoma with cells (lipoblasts) smaller than adipocytes with mutiple vacuoles and a bigger/darker central nucleus.
Describe the behavior of each histological variants of liposarcomas? What do they have in common?
Well-differentiated LPS: relatively indolent (lazy)
Myxoid/round cell LPS: intermediate
PLeomorphic variants: usually aggressive and may metastasize.
All types recur locally unless adequately exised.
What do myxoid/round liposarcoma (LPS) look like on histology?
Net-like background.
What are fibrosarcomas? Who gets them and where?
Malignant tumors composed of fibroblasts; mostly adults.
Depe tissues of the thigh, knee, and retroperitoneum.
Aggressive and recur in >50% and met in >25%.
What is a leiomyoma? Who gets them and where?
Benign smooth muscle tumor.
Uterine leiomyomas are most common neoplasm in women. May also arise in skin adn deep soft tissues.
Usually <1-2 cm; multiple lesions may be difficult to remove.
What are leiomyosaromas? How common are they, who gets them, and where?
Malignant smooth muscle tumors, makes up 10-20% of soft-tissue sarcomas.
F>M; skin and deep soft tissues of the extremeties and retroperitoneum. Superfifical are usually small with good prognosis. Retroperitoneum are large and cannot be entirely excised.
Describe the botryoid variant of Embryonal rhabdomyosarcoma; who does it occur in and what does it look like?
Infact girls with protuberant vaginal lesions, GU, H&N.
Polypoid, gelatinous mass with “bunch of grapes” appearance.
Cambium layer of tumor cells underlying the native epithelium.
What are “strap cells”
Rhabdomyoblasts: Immature skeletal muscle with dark and large nucleus
Cytoplasm strings out behind or beside it. It’s trying to make a skeletal muscle cell but cant. Eosinophilic (pink) cytoplasm.
What percentage of rhabdomyosarcoma does the alveolar subtype make up? What is the age of people who get this subtype and where does it commonly occur?
31% of RMS, most freq between 10 and 25 yo.
Deep soft tissues of extremeties
Less freq: H&N, perineum, pelvis, retroperit.
How common are synovial sarcomas? Who do they occur in and where?
5-10% of all soft tissue sarcomas.
Young adults, more commonly male.
>80% in deep soft tissues of extremeties, esp around knee.
What do synovial sarcomas look like on histology? What is their characteristic cytogenetic abnormality?
Biphasic or monophasic (two components or all looks the same) -see images
t(X;18)(p11;q11) with SYT-SSX1 or SYT-SSX2
How can FISH be used to test for synovial sarcoma?
It can detect a translocation. Synovial sarcoma is associated with:
t(X;18)(p11;q11) with SYT-SSX1 or SYT-SSX2
If there’s a translocation, you will see red AND green on the FISH b/c it makes the two colors separate out. If there’s NO translocation, you will see yellow.
What cytogenetic translocation is associated with nodular fasciitis? What does it look like on histology?
MYH9-USP6 translocation from t(17;22)
- Undifferentiated triangular looking cells with extensions - (associated with MYH9-USP6 translocations) indicates they are probably neoplastic in nature
- Extravastated RBCs with tissue culture background - (came out of vessels and are embedded in tissue) - tip off for nodular fasciitis
What is myositis ossificans? Who gets it and where?
Pseudosarcomatous proliferations in the proximal extremeties of young adults, preceded by truama in 50%
Presence of metaplastic bone; eventually the entire lesion ossifies and the intratrabecular space becomes filled with BM.
*not a malignant tumor*
