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Flashcards in Pathology MSK tumors Deck (12)
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1
Q

Lipoma

A
  • Well circumscribed, encapsulated adipose tissue w/o any areas of necrosis or hemorrhage (slow growing and painless)
  • Cells look the same as normal adipose tissue, only difference is the fibrous capsule
  • One variation: angiolipoma, these have variably-sized blood vessels mixed throughout the tumor
  • These are benign lesions, most common soft tissue mass of adults
2
Q

Liposarcoma

A
  • Encapsulated mass that is fast growing and painless, usually has central area of necrosis
  • Often is nodular and can have irregular margins
  • Histologically can see lipoblasts (dividing adipose cells w/ hyperchromatic nuclei, key finding) in high numbers, evidence of malignancy
  • Lipoblasts are variable in size and abnormal looking (strangely shaped and sized)
  • Another key finding is plexiform blood cells (capillary anastamoses) and a high degree vascularization
  • Found usually in retropreitoneum and deep soft tissue of proximal extremities
  • Malignant lesions, very rare in children
3
Q

Nodular faciitis

A
  • Develops over a few months at the site of an injury (usually forearm), often in young adults
  • Is semi-encapsulated, irregularly shaped
  • Histologically there is spindle-cell growth, indicating fibroblasts
  • At high power can see many fibroblasts, vascular proliferation and lymphocytes
  • This is a benign process, reactive to the injury
  • Malignant lesions from this process generally are slower growing than a few months
4
Q

Fibrosarcoma

A
  • Circumscribed mass, may contain some calcification
  • Has ill-defined septae and capsule, which can be eroding or infiltrating adjacent bone
  • Lesion often occurs in the thigh and around the knee (adult) or in muscles of distal limbs (infantile)
  • Pleomorphic cell population including fibroblasts (secreting collagen), plumper cells (have vacuolated cytoplasm), and occasional giant cells
  • Abnormal mitotic figures can be seen, angulated densely interlacing bundles of fibroblasts (herring-bone pattern)
  • This pleomorphic fibrosarcoma is malignant and has a poor prognosis
5
Q

Rhabdomyosarcoma

A
  • Usually in children under 20, diagnostic cell type is the rhabdomyoblast
  • Rhabdomyoblasts look like small blue round cells w/ eccentric abundant eosinophilic cytoplasm
  • There can also be elongated cells that appear strap-shaped (strap cells: very long and thin). Presence of strap cells indicates a more differentiated and thus less severe disease
  • Is a round blue cell tumor, see basophilic cells w/ hyperchromatic nuclei which are differentiated rhabdomyoblasts. These indicate a less differentiated and thus more severe disease
  • t(2;13) associated, myoD1/myogenin positive
  • These are malignant tumors and prognosis is poor
6
Q

Osteoid osteoma

A
  • Pts present w/ severe focal bone pain that worsens at night and w/ activities but is greatly relieved w/ aspirin (pain due to prostaglandin E, which aspirin inhibits production of)
  • Usually appears before age 20 (usually boys but bimodal age distribution), often in LE
  • On Xray there is a gray oval mass (nidus: lucent middle) surrounded by dense reactive bone
  • The nidus is the tumor, which has disorganized interconnected trabeculae w/ high osteoblastic activity and abundant osteoid in some areas but all of it is highly vascularized
  • The nidus can be seen expanding into the bone causing the reactive process in adjacent bone
  • These are benign neoplasms of osteocytes/osteoblasts
7
Q

Osteosarcoma

A
  • Usually has metaphyseal origins and infiltrates into surrounding soft tissue (mostly affects men and knees/long bones)
  • Bimodal incidence (older ppl usually due to sequellae of paget’s disease)
  • Associated w/ mutations in Rb, p53 genes
  • Serum alk phos levels increased
  • Can see malignant osteoblasts w/ little cytoplasm and large, hyper chromatic pleomorphic nuclei surrounded w/ osteoid (non-mineralized)
  • Lesions are usually much larger than osteoid osteoma
  • Malignant tumors
8
Q

Osteochrondroma

A
  • Usually in young adults (mostly boys), occurs at site after injury due to defect in growth plate particularly around knee
  • Has smooth but nodular surface, w/ cartilaginous cap overlying cancellous bone (bone is highly vascularized)
  • Histologically there are normal, uniform chondrocytes from the cap
  • Lesion is made of both bone and cartilage, typically occurs at long bones, often around the knee
  • Is a benign process
9
Q

Ewing sarcoma 1

A
  • Slowly growing bone mass, that is expansive and destructive (causes typical B symptoms). Mostly found in children, boys (malignant and rare)
  • Causes pain and prominent periosteal reaction, is a round blue cell tumor
  • Neoplasm arises form bone and extends into soft tissue, is made of friable soft tissue w/ areas of hemorrhage and necrosis
10
Q

Ewing sarcoma 2

A
  • There is infiltration of the medullary space by many uniform, small, round blue cells (neuroectoderm-derived)
  • This lesion destroys bone but doesn’t produce osteoid, often in the diaphyses of long bones
  • The cells have indistinct boundaries and hyperchromatic nuclei, looks similar to lymphomas
  • These lesions are positive for FLI1, the result of a t(11;22) translocation (fusion of EWS w/ FLI1)
11
Q

Pleiomorphic undifferentiated sarcoma (PUS)

A
  • Can be found in retroperitoneum/deep soft tissues
  • Most often affects men >60 yo, is Dx of exclusion where other fibrohistiocyte lesions are ruled out (fibrosarcoma, fibromatosis, ect)
  • Rarely can present as a bone lesion
  • Presents as an enlarging painful mass in proximal extremity muscles or retroperitoneum, necrosis is typical
  • Histologically see plump, pleomorphic large round spindle cells arranged in whirling pattern
  • Can see giant cells and some inflammation, positive for vimentin
  • Are malignant, and thus there isn’t much ECM b/c its filled w/ cells
12
Q

Desmoid tumor (deep-seated fibromatosis)

A
  • Borders btwn non-aggressive tumors and low-grade fibrosarcomas, usually in teens-thirties
  • Deep intramuscular or retroperitoneal mass that invades but doesn’t metastasize
  • Micro: plump long sweeping fascicles of fibroblasts infiltrating adjacent tissue
  • Cells less pleomorphic than PUS, look more like fibrosarcoma cells
  • Fewer cells than PUS or fibrosarcoma b/c is not malignant