[B] 1.78 Melanocytic tumors, the important tumors of nervous tissue. Mixed tumors

Question 1

Melanocytic tumours

Answer 1

• Melanoblast, melanocyte origin
• Skin & hair follicle
• Pigment in melanosomes
• Melanocytoma (Benign)
• Melanoma (Malignant, but not obvious from the name)

Question 2

Melanocytoma

Answer 2

• Epiderma, derma, adnexal (of uterus)
• Mainly dogs (Vizsla) & Horse (Arabian)
• Aged animals

Question 3

Melanoma

Answer 3

• Malignant, aggressive neoplasm
• Mucocutaneous junction & oral cavity
• Rarely on hairy skin
• Mostly in dogs
• Ranges from: Very pigmented → Amelanotic

Question 4

Benign muscular tumours

Answer 4

• Rhabdomyoma
• Leiomyoma
• Cardial rhabdomyoma

Question 5

Rhabdomyoma

Answer 5

• Rhabdomyoblast origin (Skeletal muscle)
• Larynx
• Extremely rare

Question 6

Leiomyoma

Answer 6

• Tumour of smooth muscle tissue
• Dog: Vagina & GI tract
• Leiomyofibroma occurs (frequent)

Question 7

Malignant muscular tumours

Answer 7

• Rhabdomyosarcoma
• Leiomyosarcoma
• Cardial rhabdomyosarcoma

Question 8

Tumours of nervous tissue

Answer 8

• Neoplasms affecting older animals, therefore mostly in Cats & Occurs in CNS and PNS
• Tight connection between pathology and clinical history

Question 9

List the primary CNS tumours

Answer 9

• Astrocytoma
• Oligodendroglioma
• Oligoastrocytoma
• Ependymal & choroid plexus tumours
• Medulloblastoma
• Neuroblastoma
• Meningioma

Question 10

Astrocytoma

Answer 10

• Subgroup of gliomas
• Divergent group, many histotypes (Diffuse or well-circumscribed)
• 15% of all CNS tumours
• Dogs (brachycephalic)

Question 11

Oligodendroglioma

Answer 11

• Oligodendrocytic origin
• Well-circumscribed, but infiltrative tumour
• Dogs (Brachycephalic breeds)
• Frontal regions of hemispheres
• Gelatinous

Question 12

Oligoastrocytoma

Answer 12

• Diffusely infiltrative type of glioma
• Carries characteristics of astrocytoma and oligodendroglioma

Question 13

Medulloblastoma

Answer 13

• Primitive neuroectodermal tumour
• Affects the cerebellum
• In older dogs & cats

Question 14

Meningioma

Answer 14

• Originates from meningeal cells
• Most frequent primary CNS tumour in dogs & cats
• Boxer & golden retriever
• Usually solitary, well-circumscribed
• Also in spinal cord, intradural

Question 15

Primary PNS tumours

Answer 15

• Schwannoma
• Neurofibroma
• Malignant nerve sheath tumour

Question 16

Mixed tumours

Answer 16

• Composed by more cell types
• Pluripotent / totipotent stem cells
• Goes through on divergent differentiation
• Canine mammary gland: Benign mixed tumour
• Teratoma & Teratocarcinoma

Question 17

Canine mammary gland: Benign mixed tumour

Answer 17

• Neoplastic epithelial component:
  
  • Glandular, tubular: Luminal epithelium
  • +Myoepithelium
  • +Mesenchymal elements
    
    • Cartilage
    • Bone

Question 18

Teratoma & teratocarcinoma

Answer 18

• From totipotent stem cells
  
  • (Testicle, ovary)
• E_cto-, meso-, and endodermal_ components in the tumour