77. Melanocytic tumors, the important tumors of nervous tissue. Mixed tumors

Question 1

Melanocytic tumours

Answer 1

Melanoblast, melanocyte origin (neuroectodermal)
Skin, hair follicle are the anatomic locations (basal layer of epidermis)
Pigment in melanosomes
Melanocytoma (benign tumour)
Melanoma (malignant, however the name does not show this)

Question 2

Melanocytoma

Answer 2

Epidermal, dermal or adnexal
Mostly affects dogs (vizsla!), horses (Arabian) Aged animals

Question 3

Melanoma

Answer 3

Malignant, agressive neoplasm
Mucocutaneous junction!!, oral cavity
Rarely (10%) on hairy skin (head, scrotum)
Mostly in dogs
Very pigmented

Question 4

Rhabdomyoma

Answer 4

Extremely rare (also is human)
Rhabdomyoblast origin (skeletal muscle)
benign

Question 5

Leiomyoma

Answer 5

 Tumour of smooth muscle tissue
 Dog: vagina, GI tract

Question 6

Cardial rhabdomyoma

Answer 6

cardiac muscle

Question 7

Astrocytoma

Answer 7

 Subgroup of gliomas
 Divergent group, many histotypes (diffuse or well-circumscribed)
 15% of all CNS tumours
 Mostly in dogs, brachycephalic breeds

Question 8

Oligodendroglioma

Answer 8

Oligodendrocytic origin
Well-circumscribed, but infiltrative tumour
Mostly in dogs, brachycephalic breeds

Question 9

Oligoastrocytoma

Answer 9

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

Question 10

Medulloblastoma

Answer 10

Primitive neuroectodermal tumour
Affects the cerebellum
In older dogs and cats

Question 11

Meningioma

Answer 11

Originates from meningeal cells
 Most frequent primery CNS tumour in dogs (45%) and cats (60%)
 Boxer, golden retriever!
 Also in spinal cord, intradural (C, L-S)

Question 12

Schwannoma

Answer 12

Benign Schwann cells

Question 13

Neurofibroma

Answer 13

Benign, Schwann cell + fibroblast + perineural cells

Question 14

Perineurioma

Answer 14

very rare!
* Modified Schwann cells
* „onion bulb” pattern around axon

Question 15

Teratoma and teratocarcinoma

Answer 15

mixed tumor
from totipotent stem cells (normally in testicle, ovary, sequestred mesodermal embryonic remnants) → both ecto-, meso- and endodermal components in the tumour