[B] 1.76 Benign mesenchymal tumors

Question 1

Most neoplasms originate from…

Answer 1

One cell type:

• Mesenchymal
• Epithelial

Question 2

Identification of tissue

Answer 2

• HE staining
• Immunohistochemistry: Role in exact diagnosis

Question 3

Immunohistochemistry: How it works

Answer 3

Based on antigen-antibody reaction

• Molecular pathologic reaction
• Binds to:
  
  • Structural/functional proteins
  • Glycoproteins
  • Polysaccharides
• Diagnosis and/or prognosis

Question 4

Mesenchymal tumours refer to which tissues?

Answer 4

• Connective
• Muscular
• Vascular
• Haemolymphatic

Question 5

Give the benign tumours of the connective tissue

Answer 5

• Fibroma (Collagen fibres)
• Myxoma (Embryonic)
• Lipoma (Adipose)
• Chondroma (Cartilage)
• Osteoma (Bone)
• Osteochondroma

Question 6

Fibroma

Answer 6

Tumour of fibroblasts

• Durum (“firm”) et molle (“soft”) types
• Frequently mixed with other tissue types
• Peripheral odontogenic fibroma (POF)
  
  • Neoplasm of the peridontal ligament
  • Frequent in canine

Question 7

Myxoma

Answer 7

Gelatinous connective tissue, fibroblast origin

• Mucin-rich stroma
• Differential: Oedematous fibroma
• Mostly in subcutis
• Rare

Question 8

Lipoma

Answer 8

• Very high incidence (especially in dogs)
• Predisposition:
  
  • Bitch, castrated siamese cats
• Rarely:
  
  • Fibrolipoma, angiolipoma, infiltrative lipoma
• Horse:
  
  • Mesenterial lipoma (pedunculated)

Question 9

Chondroma

Answer 9

• Mostly hyaline cartilage
• Primarily bone origin
  
  • Enchondroma (medullary cavity)
  • Ecchondroma (other skeletal locations)
• Older dogs & sheep
• Slow growth - Can cause bone deformity

Question 10

Chondroma is often a component in…

Answer 10

Benign mixed mammary gland tumour

Extraskeletal chondroma

Question 11

Osteoma

Answer 11

Neoplasm of bony tissue (compound or trabecular)

• Usually solitary, affects the bones in the head
• Often a component in canine benign mixed mammary gland tumour (extraskeletal osteoma)

Question 12

Osteoma: Differential diagnoses

Answer 12

• Reactive ossification (callus) after trauma
• Ossifying fibroma: Affects horse’s jaw
• Osteophyte
• Exostosis

Question 13

Osteochondroma

Answer 13

Bony proliferation capped with cartilage, endochondral ossification in the bone

• Usually solitary, sometimes multiplex
• Tumour or dysplasia
• Young dogs & horses
• Cat: Osteochondromatosis
  
  • FeLV, FeSV role
  • Progressive growth, different localisation