Path Block 6 - Bone

  1. What are the functions of bone?
    • Mineral homeostasis
    • House meatopoietic elements
    • Provide mechanical support for movement
    • Protect viscera
    • Determine body size and shape
  2. What is bone composed of?
    • Mineral Phase (60%) : Ca, Phos, Mg - stiffness
    • Type I Collagen (30%) - tensile strength
    • Type V Collagen (1.5%)
  3. How is bone collagen organized?
    • Lamellar (mature)
    • Women (immature
  4. What cells are involved in making/resorbing bone?
    Osteoblasts: deposit type I collagen, mineralization, become osteocytes

    Osteoclasts: multinucleated giant cells, bone resorption, have dendritic connections to communicate with each other
  5. What is cartilage made of?  And what are the types of cartilage?
    • Type II collagen
    • Hyaline (most abundant)
    • Elastic (ear)
    • Fibrocartilage (intervertebral discs, tendon attachments)
  6. What are the two types of osteogenesis?
    Transformation of pre-existent mesenchymal tissue into bone

    • Intramembranous
    • Endochondral
  7. What is intramembranous ossification and where does it occur?
    direction transformation of neural crest-derived mesenchymal tissue into bone.

    Calvarium and clavicle
  8. What is endochondral ossification and where does it occur?
    Mesenchymal cells first diferentiate into cartilage, later replaced by bone.

    Tubular bones, flat bones, epiphysoid bones, irregular bones --> vertebral column, pelvis, extremities.
  9. What are the 5 stages of endochondral ossification?
    • 1) Reserve cartilage
    • 2) Zone of proliferation
    • 3) Zone of hypertrophy
    • 4) Zone of degeneration, apoptosis, mineralization
    • 5) Zone of ossification (primary spongiosa)
  10. What happens during the second phase of endochondral ossification?
    Zone of proliferation - chondrocytes secrete cartilage-specific extracellular matrix.
  11. What happens during the third phase of endochondral ossification?
    Chondrocytes cease to divide and hypertrophy - modifying the matrix they produce to allow its mineralization with calcium carbonate.
  12. What happens in the 4th phase of endochondral ossification?
    Invasion of cartilage by blood vessels and subsequent death of hypertrophic chondrocytes through apoptosis - this space becomes BM.

    Cells differentiate into osteoblasts - start forming bone matrix (osteoid) in partially degraded cartilage.
  13. What happens in the 5th phase of endochondral ossification?
    New bone is added to the periphery (periosteoum).  THe internal region is reabsorbed to form the BM cavity via osteoclasts.
  14. What are dysostoses?
    developmental bone anomalies resulting from localized problems (migration, cellular condensations) - mutations in certain transcription factors
  15. What are dysplasias?
    mutations that globally affect cartilage and bone - signaling molecules & matrix components
  16. What mutation is associated with achondroplasia and how is it inherited?
    • FGFR3 mutation
    • AD
    • 80% from new cases (mostly on paternal allele)
  17. What are the clinical features of achondroplasia?
    • Shortened proximal extremities with normal trunk length
    • Enlarged head w/ bulging forehead and depression of the root of the nose
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    What is seen here and what are the other clinical features?
    Thanatophoric dysplasia - curved shape femur seen.

    • 40% lethal skeletal dysplasias
    • short ribs and extremities
    • vertebral bodies with U or H shape on frontal projections
    • Frontal bossing and macrocephaly
    • Small chest cavity with bell-shaped abdomen
    • Respiratory insufficiency
  19. What mutation is involved in thanatophoric dysplasia?
    3 different FGFR3 mutations are responsible for 85% of cases.

    Transmembrane domain: milder form, achondroplasia

    Tyrosine kinase domain or in extracellular domain: lethal form, thanatophoric dysplasia
  20. What are the clinical features of osteogenesis imperfecta?
    • blue sclera
    • 4 types - lethal form present in 25% skeletal dysplasias
    • intrauterine growth retardation
    • severe osteopenia
    • multiple fractures
    • short and curved extremities
    • small thorax w/ hypoplastic lungs - respiratory insufficiency 
  21. What is happening incorrect in osteogenesis imperfecta?  And how is this inherited?
    Defect of synthesis of assembly of procollagen type I osteoblasts

    AD - most common inherited disorder of connective tissue

  22. What is osteoporosis?  
    Reduced bone mass predisposing to fracture

    • Localized: disuse
    • Entire skeleton: metabolic bone disease

    ~1 million/year have fracture in US
  23. What are the components of peak bone mass?  What contributes to osteporosis?
    Genetic factors + nutrient + physical activity = peak bone mass

    Menopause: decreased estrogen, increased RANK expression, increased osteoclast activity, increased IL-1, IL-6, TNF

    Aging: decreased physical activity, decreased osteoblasts, dedcreased growth factors

    Osteoclasts mainly affect bones with increased surface area (vertebral bodies)
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    What is seen here?
    Mosaic pattern of Paget Disease - primary bone disorder

    • Severe bone deformities
    • Predispose to malignant tumors
    • Late adulthood (70 yrs)
  25. What mutation is involved in Paget disease?
    SQSTM1 mutation - enhances RANK signaling

    7X more common in 1st degree relatives
  26. What are the 3 stages of Paget disease?
    What is the net result?
    • 1) Osteolytic stage
    • 2) Mixed osteoclastic/osteoblastic 
    • 3) Burn-out quiescent osteosclerotic stage

    Net gain in bone mass, newly formed bone disordered and vulnerable to fracture
  27. What are Rickets and Osteomalacia?
    Lack of vitamin D or some disturbance in metabolism

    Rickets: children
  28. What is hyperparathyroidism?
    Primary: tumor or hyperplasia

    Secondary: prolonged hypocalcemia; increased PTH detected by osteoblasts which increase osteoclastic activity - bone loss predisposes to microfractures.  Hemorrhage + fibrosis tissue = brown tumor
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    Brown tumor of hyperparathyroidism
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    Multinucleated osteoclasts in brown tumor of hyperparathyroidism.
  31. What are the different types of fractures?
    Pathologic: break occurs in bone already altered by disease process.

    Stress: develops slowly following a period of increased physical activity with repetitive loads.

    Pseudoarthrosis: if nonunion allows too much motion, central portion of the callus undergoes cystic degeneration, and the luminal surface can become lined by synovial-like cells, creating a false joint.
  32. What causes avascular necrosis and how does it present clinically?
    Ischemia d/t fracture, idopathic, or corticosteroid administration

    • Subchondral: chronic pain
    • Medullary: clinically silent

    10% of 500K joint replacements/year in U.S.
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    Avascular necrosis
  34. What is osteomyelitis caused by and how does it reach the bone?
    Hematogenous spread, extension from contiguous site, direct implantation.

    Staphylococcus aureus in 80-90% cases of pyogenic osteomyelitis where organism recovered.

    Mixed bacterial infections in direct spread or during surgery/open fractures

    SCD: Salmonella

    50% cases no organism isolated
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    Osteomyelitis with mixture of fibrosis and inflammatory cells instead of fat.

    • Plasma cells: chronic osteomyelitis
    • Neutrophils: acute
  36. How does osteomyelitis manifesT?
    Fever, chills, malaise, pain over affected region

    X-ray: lytic focus surrounded by zone of sclerosis

    Blood cultures may be positive

    Biopsy and bone cultures may be required to identify pathogen
  37. How is osteomyelitis cured?
    Antibiotics and surgical drainage

    5-25% cases fails to resolve and persists as chronic infection

    Acute spontaneous flare-ups with no obvious cause, even after yrs of dormancy.
  38. What is the prevalence and incidence of bone tumors?
    In US, 3/1000 malignant tumors is a bone tumor.

    Incidence: 1/100,000 per year
  39. What age differences are seen in bone tumors?
    • Adult > malignancy
    • Children > benign
  40. What tumors are seen in adolescence?
    Osteosarcoma, Ewing's Sarcoma
  41. What tumors are seen in young adults?
    Giant cell tumor
  42. What tumors are seen in elderly?
  43. What tumors are seen in the knee?
    • 1/2 of osteosarcomas
    • Giant cell Tumors
    • Non-ossifying fibromas
    • >1/3 of ostechondromas
  44. What tumors are seen in the epiphysis of long bones?
    • Chondroblastoma
    • Giant cell tumor
  45. What tumors are seen in the central/axial location?
    • Chondrosarcoma
    • 1/2 of osteoblastomas
  46. What tumors are seen in the diaphysis of long bones?
    • Ewing sarcoma
    • >1/3 of chondrosarcomas
  47. What is osteochondroma, where does it occur, and its associated mutation?
    Exotosis - most common benign tumor of bone

    Starts in growth plate and migrates towards metaphysis as patient grows with cartilagenous cap on top.

    Malignant transformation rare - EXT-1 is the germline mutation that increases the risk in hereditary multiple exostoses (AD).
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    Osteochondroma with a mushroom/polypoid appearance with a stalk.

    Rarely seen with broad base.
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    Osteochondroma with cartilagenous cap with endochondral ossification
  50. Who is chondroblastoma seen in?  Where is it located?  What is the pathology and treatment?
    • Rare, adolescents, M>F
    • Epiphysis of knee or proximal humerus
    • Benign, but rare metastases

    Circumscribed proliferation of chondroblasts with hyaline matrix and chicken-wire calcification.

    Tx: curretage, common recurrence
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    Chondorblasts with chickenwire calcification seen in chondroblastoma.
  52. Who is chondrosarcoma seen in?  Where is it located?  How is graded? Variants?  Survival?
    2nd most common malignant tumor of bone (26%) - bulky tumor of malignant cartilage

    Older adults (60s-70s), M>F

    Central skeleton (except clear cell variant) - pelvis & ribs, femur, humerus, medullary location

    Most low grade (1-3) based on degree of cellularity

    Variants: de-differentiated, myxoid, clear cell, mesenchymal, juxtacortical

    Survival: 80-90% (1 &2), 29% Gr 3(lung)
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    Popcorn-like cartilagenous matrix of chondrosarcoma.
  54. What are osteoid osteomas? Where are they located? Tx?
    • Benign bone forming tumor
    • Long bones, femur, tibia
    • <2cm
    • Night pain
    • Responds to aspirin
    • Radiolucent lesion w/ sclerotic cortex
    • Well circumscribed
    • Woven bone trabeculae/osteoid rimmed by osteoblasts (nidus)

    Tx: curettage, may recur if not completely removed
  55. What is osteoblastoma?  Where is it located?
    • Benign bone forming tumor
    • Vertebrae or long bone metaphysis

    • >2cm
    • painful
    • not responsive to aspirin
    • expansile radio-lucency with mottling
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    Nidus: woven bone trabeculae/osteoid rimmed by osteoblasts

    See in osteoid osteoma
  57. What is osteosarcoma?  Who is affected? Where is it located? What is treatment?
    • Most common malignant bone tumor
    • Destructive lesion, Codman's triangle.
    • Infiltrative - extending into soft tissue.  Malignant cells producing osteoid.

    • Bimodal (15 yrs and 55-80 yrs). M>F. 
    • Hematgenous spread to lungs common.

    Metaphysis of long bones

    Tx: Chemotherapy and surgical ressection
  58. What is the pathogenesis of osteosarcoma?
    Inherited mutant allele of RB gene - hereditary retinoblastoma: marked increase (1000 fold) in osteosarcoma.

    Mutation of p53 suppressor gene - Li-Fraumeni: germinline p53 mutation - bone and soft tissue sarcomas, early onset breast cancer, brain tumors, and leukemia

    Prior irradiation
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    Codman's triangle in osteosarcoma.

    Destructive lesion because it is not respecting tissue planes
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    Telangiectatic osteosarcoma - tumor has tendency to have abundant blood leaks within it.
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    tumor cells not only forming osteoid but also cartilage
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    osteosarcoma- fibroblastic

    spindled, elongated cells
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    surface osteosarcoma

    arise from metaphysis, medullary cavity completely spared b/c this tumor arises from surface of long bones
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    post radiation - osteosarcoma

    radiation to scull for squamous cell carcinoma - years later developed aggressive osteosarcoma in that location
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    Non-ossifying fibroma - metaphyseal fibrous defect

    • common developmental cortical defect
    • incidental finding or pathologic fracture
    • sharply demarcated cellular lesion of fibroblasts and histiocytes
  66. WHat is fibrous dysplasia?  What are the two kinds?  What is the treatment?
    Developmental arrest of bone

    Monostotic: most common, adolescents, ribs, mandible, femur

    Polyostotic: infancy/childhood, crippling deformities, craniofacial involvement 

    Tx: conservative, except polyostotic form
  67. What is seen on x-ray in fibrous dyplasia and in pathology?
    Circumscribed oxteolytic "ground glass" lesion in diaphysis with sclerotic rim

    Haphazard curvilinear bone trabeculae (Chinese characters) surrounded by fibroblastic stroma
  68. What is McCune Albright syndrome?
    Polostotic fibrous dysplasia with endocrinopathies and cafe-au-lait spots.

    • Rare, F>M
    • Activating mutations of GNAS(GTP-binding protein)
    • Result in excess cAMP leading to endocrine gland hyperfxn
    • Sexual preocicty, acromegaly, and Cushing syndrome
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    Fibrous dysplasia
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    What is seen here?  Where does it occur?  Who does it happen in?
    • Giant Cell Tumor
    • Benign, locally aggressive
    • Knee, proximal humerus, epiphysis
    • Young adults (skeletally mature)
    • F>M
    • May destroy cortex and extend to soft tissue
    • Tx: Curretage
  71. What is a solitary (unicameral) bone cyst?  Where does it occur?  How do you treat?
    Multiloculated cyst filled w/ clear to bloody fluid.

    Proximal epiphysis humerus (1/2) and femur (1/4)

    Tx: Curretage & packing, frequently recurrs
  72. Who and where does an aneurysmal bone cyst effect?  What is seen on X-ray and pathology?
    • Any bone, long bone metaphysis and vertebrae
    • Adolescents, F>M

    X-Ray: lytic well-defined lesion which distorts bone, may extend into soft tissue

    Pathology: cavernous blood-filled spaces surrounded by fibrous septae.
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    Aneurysmal Bone Cyst - normally bone replaced by cystic cavity that contains blood
  74. Who gets Ewing Sarcoma?  Where does it occur?
    SEcond most common malignant bone tumor in childhood.

    • Adolescents, young adults
    • Painful, often enlarging mass
    • Diaphysis of long tubular bones, ribs, and pelvis
  75. What is the pathogenesis of Ewing Sarcoma?
    t(11;22) EWS (22) fused with FLI-I (11)
  76. What is the pathology and X-ray of Ewing Sarcoma? What is the treatment?
    • Pathology: primitive small round cells with neural phenotype
    • Contain abundant glycogen
    • Hemorrhage and necrosis common

    X-Ray: destructive intramedullary lesion, "onion-skin" pattern of periosteal reaction in response to rapid growth

    Tx: chemo and surgery, radiation may be added
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    • Ewing Sarcoma
    • Onion-skin pattern
    • Small round blue cell tumor that usually expresses CD99
  78. What are the common metastatic tumors in adults and children?  Where do they occur?
    Adult: prostate, breast, kidney, thyroid, lung

    Children: neuroblastoma, Wilms, osteosarcoma,  Ewing sarcoma, rhabdomyosarcoma

    Usually multifocal in axial skeleton
  79. What are the two types of metastatic bone tumors?
    Lytic: kidney, lung, thyroid, GI, breast - stimulate osteoclastic bone resoprtion

    Blastic: prostate & breast
  80. What is osteoarthritis and who is affected where?
    • Wear and tear and problems with repair
    • AKA degenerative joint disease
    • Aging & mechanical effects
    • Knees and hands: women
    • Hips: men
  81. What factors genetic play a role in OA? What other factors?
    • Chromosomes 2  & 11
    • Increased bone density and estrogen increases risk
  82. What joints in the hands are affected in OA?
    Heberden's (distant) and Bouchards nodes
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    • OA
    • 1) Eburnated articular surface
    • 2) Subchondral cyst
    • 3) Residual articular cartilage
  84. What is the clinical course of OA?
    • May be disabling
    • Hand fxn rarely impaired, even if pain and stiffness remain.
    • Pain in knee or hip may decrease even as disease progresses
  85. What is rheumatoid arthritis and who does it affect?  What joints are affected?
    • chronic systemic inflammatory disorder
    • common age 40-70, F>M
    • often progresses to destruction of articular cartilage and ankylosis
    • may affect many tissues & organs
    • autoimmunity
    • microbe may start rxn and ultimately cause cross rxn w/ antigens in joints
    • affects PIP and MCP
  86. What are the characteristic features of RA?
    • infiltration of synovial stroma by dense perivascular CD4+ T cells, plasma cells, and macrophages
    • increased vascularity d/t vasodilation and angiogenesis
    • organizing fibrin covering synovium and floating joint space
    • osteoclastic activity in underlying bone forming juxta-articular erosions, subchondral cysts, osteoporosis
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    RA with lymphoid aggregate and dilated blood vessels
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    Pannus formation: mass of synovium and stroma, inflammatory cells, granulation tissue and fibroblasts, which grows over and erodes articular cartilage

    Pannus may bridge apposing bones, forming fibrous anyklosis, which ossifies and forms bony ankylosis
  89. What is the clinical progression of RA?  What can be used to test?  What causes fatalities?
    • Variable clinical course
    • Generally small joints affected before larger ones
    • No specific diagnostic test: many patients have serum rheumatoid factor: IgM antibody reactive with Fc portion of patients' own IgG - may not be present throughout course of disease

    Fatalities usually d/t systemic amyloidosis and vasculitis, or iatrogenic effects to therapy
  90. What is juvenile RA?
    • Before age 16
    • F>M (except in systemic where it is equal)
    • Heterogenous group of chronic arthritides
    • Fxn disability
    • Variants: oligoarticular(<5 joints), polyarticular, systemic
  91. What is seronegative spondyloarthropathies? What are the clinical variants?
    What is it associated with?
    • Genetically predisposed individuals
    • Initiated by environmental factors, especially prior infections or exposures
    • Manifestations are immune mediated, maybe triggered by T-cell response to unknown antigens

    • Clinical variants:
    • ankylosing spondylitis (usually affects lumbar spine)
    • Reactive arthritis
    • Psoriatic arthritis
    • Arthritis associated w/ IBD

    Overlapping clinical features, many associated with HLA-B27 and triggering infection
  92. What are the reasons for primary and secondary gouty arthritis?

    What does gout look like?
    • Primary: 
    • unknown enzyme defect with increased urate production or decreased urate excretion

    • 2ndary:
    • increased NA turnover, chronic renal disease, Lesch-Nyhan (increased urate production)

    Urates-needle shaped, negative birefringent crystals, tophi (large aggregates of urate crystals surrounded by intense inflammatory rxn)
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    Acute Gouty Arthritis

    needle shaped, negative birefringent crystals
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    Tophi: large aggregates of urate crystals surrounded by intense inflammatory rxn
  95. What is pseudogout?  What does it look like?
    Calcium pyrophosphate crystal deposition (chondrocalcinosis)

    Etiologies: sporadic, hereditary, secondary

    Chalky white friable deposits seen histologically as oval blue-purple aggregates

    Individual crystals (.5-5um), weakly positively birefringent, rhomboid shapes
  96. What are the small minority of soft tissue neoplasms associated with genetic syndromes?
    • Neurofibromatosis type 1 (neurofibroma, MPSNT)
    • Gardner syndrome (fibromatosis)
    • Li-Fraumeni syndrome (soft tissue sarcomas)
    • Osler-Weber-Rendu syndrome (telangiectasia)
  97. What are important prognostic factors in soft tissue tumors?
    • Grade: I to III 
    • based on degree of differentation/pleomorphism
    • average number of mitoses 
    • Extent of necrosis

    Size (> or < 5cm), depth, stage (metastasis)

    superficial have better prognosis than deep lesions
  98. What is a lipoma?
    most common soft-tissue tumor of adhulthood

    subclassified according to particular morphologic feature

    conventional lipomas: 12q14-q15

    well encapsulated mass usually cured by simple excision
  99. What age are liposarcomas present?  What are the different histologic variants?
    • 40s-60s
    • Proximal extremities & retroperitoneum

    • well-differentiated: indolent
    • myxoid/round cell: intermediate
    • pleomorphic: aggressive
  100. What are the two types of fibromatoses?
    • Superficial: palmar (Dupuytren contracture), plantar, penile (Peyronie disease)
    • may stabilize and resolve spontaneously, some recur

    Deep-seated(Desmoid tumors): behavior lies btwn benign fibrous tumors and low grade fibrosarcomas.  frequently recur, in teens-30s, some associated with Gardner syndrome, mutations in the APC or beta-catenin genes. 
  101. Where does fibrosarcoma happen?  How often do they recur and metastasize?  What markers are positive?
    • Deep soft tissues of extremities
    • Recur >50%
    • Metastasize >25%
    • All markers but vimentin are negatine
  102. What is hemangioma and what are the two types?
    • Benign tumors of blood vessels, increased numbers of normal or abnormal vessels
    • Very common, infancy/childhood

    Capillary: composed of capillaries: congenital, infantile/juvenile, lobular

    Cavernous: venous malformations, usually deep-seated
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  104. What are the etiologic factos of angiosarcoma? And where are they located?
    • Lymphedema: post mastectomy - loss of afferent lymphatics, immunologically privileged site
    • Radiation
    • Carcinogens: thorotrast, insecticides, vinyl chloride
    • AV fistulas, foreign material

    cutaneous: most common, head and neck( Scalp and forehead), elderly, beneath hair (sun exposure)
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    cutaneous angiosarcoma
  106. What is Kaposi's sarcoma associated with?  And what are the different forms?
    • HHV-8
    • Classic: elder men of Mediterranean descent; skin, indolent
    • Africa endemic: young Bantu children of S. Africa; lymph nodes, aggressive
    • AIDs-associated: skin or any organ; spreads widely, but usually not lethal
  107. Who is leiomyosarcoma seen in?  Where does it affect?  What is the prognosis?
    • Adults, F>M
    • skin and deep soft tissues of the extremities and retroperitoneum
    • superficial = good prognosis
    • retroperitoneum = large, cannot be entirely excised, local extension and metastatic spread
  108. What are the 3 types of rhabdomyosarcoma and what are their features?
    Embryonal: 49% RMS, more frequent <10 yrs, head and neck, GU tract, deep soft tissues of extremities, pelvis, retroperitoneum

    Alveolar: 32% RMS, age 10-25, deep soft tissues of extremities (less in head, neck, perineum), t(2;13) or t(1;13)

    Pleomorphic: older individuals
  109. What are the types of tumors of unknown histogenesis?
    • Synovial sarcoma
    • epithelioid sarcoma
    • alveolar soft part sarcoma
  110. Who has synovial sarcoma and what is the translocation?  Where is it located?
    • Young adult males
    • Deep tissue of extremities, KNEE
    • t(X;18)(p11;q11)
    • histologically biphasic or monophasic
  111. What are the prognostic indicators for bone and soft tissue sarcomas?
    Grade, size, location (depth), metastases(most important)
  112. What is the common metastatic site of bone and soft tissue sarcomas?
  113. How many new soft tissue sarcomas and bone sarcomas are diagnosed per year in the US?
    8000 and 2500
  114. What is the most common malignant bone lesion in patients >40?
    metastatic carcinoma
  115. What is the most common primary bone tumor?
    multiple myeloma
  116. What is the most common bone tumor of children?
  117. What should you obtain prior to any biopsy or excision of a soft tissue mass?
  118. What are the requirements for a biopsy?
    • longitudinal
    • within a single compartment
    • made with the definitive resection in mind
    • performed by the definitive surgeon
Card Set
Path Block 6 - Bone
Bone & CNS