Pathology of MSK Tumours I Flashcards
What are some practical issues associated with MSK tumours?
When and what to biopsy, don’t send a fine needle aspirate from a superficial 10cm mass, diagnosis relies on examination of all of lesion as well as other tests and radiological correlation
What are soft tissue lesions characterised by?
Genetic abnormalities
What is karyotyping?
Culture cells and then arrest during cell division, can be issues with quality of cells, useful overview of chromosomal structure, will not detect small or subtle lesions
What is FISH?
Useful for known translocations, can “paint” relevant small area of chromosomes, if signals move together then its translocation, can be done on fixed tissue
How is immunohistochemistry used?
Know certain cells express certain proteins, pigment placed on the antibody to target protein, any pigment staining left means the protein is present
What are some examples of benign tumours?
Ganglion cyst, superficial fibromatoses, deep fibromatosis, giant cell tumour, fibrous cortical defect, fibrous dysplasia
Where do ganglion cysts tend to form?
Peripheral and near joint capsule/ tendon sheath, common around wrist
Why do ganglion cysts form?
Due to degenerative changes within the connective tissue
Why are ganglion cysts not true cysts, and how they appear histologically?
They have no epithelial lining; space with myxoid material, secondary inflammatory changes
What are some examples superficial fibromatoses?
Dupuytren’s = common, more common in men, average age is 60, idiopathic lots of associations (alcohol, diabetes, anticonvulsants)
Knuckle pads, Plantar, Penile (Peyronie’s)
What are some features of deep fibromatosis?
Mesenteric or pelvic, desmoid tumours, associated with Gardner’s syndrome (FAP)
What are some examples of giant cell tumours?
Pigmented villonodular synovitis = large joints, more destructive and diffuse in joint space, difficult to excise and often recur
Giant cell tumour of tendon sheath = digits, small nodules and easily excised, occasional recurrence
Where are the nuclei of fat cells?
At the edge of the cell (are small)
What are some features of an angiolipoma?
Usually multiple and peripheral, vascular with fibrin thrombi, painful subcutaneous lesion
What are the components of the ANGEL acronym for types of fat tumours?
Angiolipoma, Neuroma (traumatic), Glomus tumour (nail beds etc), Eccrine spiradenoma (skin adnexal tumour), cutaneous Leiomyoma (of erector pilae)
What are some tumours that can arise from smooth muscle?
Leiomyomas = one of most common tumours in body
Leiomyosarcomas = uncommon
Both may grow from large vessel walls
What are present on IHC of smooth muscle tumours?
Actin, desmin, caldesmon
What are the benign tumours that can form in skeletal muscle?
Rhabdomyomas = very rare, cardiac only found in children, head and neck are uncommon but found in older patients
What are some features of embryonal rhabdomyosarcoma?
Occurs in childhood, genital tract (botyroides), GU tract, head and neck (periorbital) and common bile duct are all sites, caused by deletion Xp11.15
What are some features of alveolar rhabdomyosarcomas?
Young adults, has many sites, caused by PAX translocation (t2:5)
What are some features of pleomorphic rhabdomyosarcoma?
Rarest form, older age group, MYOD1 and myogenin on IHC
What tumours occur in cartilage?
Sarcomas
What age group tends to get cartilage sarcomas, and what are the exceptions?
Tend not to affect paediatrics and is more common in patients age 40-50; exceptions are clear cell and mesenchymal sarcomas
Where to cartilage sarcomas tend to develop?
Axial skeleton and head and neck
What are the malignant bone tumours called, and who tends to get them?
Osteosarcomas; paediatric age group in long bones
How can osteosarcomas be predicted?
From destructive radiology (Codman’s triangle)
What is the rule for diagnosing osteosarcomas?
Any tumour that produces osteoid is and osteosarcoma until proven otherwise
What are two tumours of unknown origin?
Synovial and Ewing’s sarcomas
Who gets Ewing’s sarcomas, and where do they tend to develop?
Occur in children and adolescents in any soft tissue or bony location (often long bones in adolescents)
What are some features of Ewing’s sarcoma?
Destructive, rapidly growing, highly malignant, uncertain histogenesis, either primitive mesenchymal or neuroectodermal in origin, small round blue tumour cells
What genetic abnormality causes Ewing’s sarcoma?
t(11;22)(EWS-FL11)
What is the most common group of adult malignancies?
Carcinomas
What are some indications that a tumour is a sarcomatoid carcinoma?
Look for dysplasia, can express any protein, often actin positive, look hard for epithelial markers (also positive in epitheloid and synovial sarcomas)
What are some conditions that may be mistaken for sarcomatoid carcinomas?
Pseudosarcomas, tissues undergoing repair (may look atypical)
What are some examples of reactive lesions?
Nodular fasciitis, myositis ossificans, rheumatoid, Heberden’s nodes, Buscchard’s nodes,, gouty tophi, abscesses, inflammatory myofibroblastic tumours
What are some features of nodular fasciitis?
Any age group, rapid growth, small, sometimes history of trauma, very chaotic appearance, haemorrhage, pseudocystic spaces, large atypical cells, frequent and normal mitoses
What are some features of myositis ossificans?
Reactive small and short history, preceding trauma, occurs in big muscles (quadriceps, gluteus), shows zonation
What are some features of rheumatoid?
Nodules common, can occur in elbow, necrobiotic granulomatous inflammation
What are some differentials for rheumatoid?
Deep granuloma annulare, epitheloid sarcoma
What are some features of the cytology of connective tissue diseases?
Joint fluid examined under cross-polarised light to detect crystals, crystals lost during processing and formalin, need fresh specimen to diagnose with microscopy, negative birefringence (needle shaped crystals)
What does cytology of connective tissue diseases show?
Amorphous eosinophilic debris and inflammation
How does amyloid protein appear when using birefringence?
Apple green birefringence with congo red staining
