76. Benign mesenchymal

tumours

77. Malignant

mesenchymal tumours Anna Szilasi DVM

2019

Tissue origin

Most neoplasms originate from one cell type

Mesenchymal

Epithelial

Nomenclature usually refers to the origin

Identifiable with hematoxylin&eosin routine staining

Immunohistochemistry (IHC): role in exact diagnosis

Based on antigen-antibody reaction

Molecular pathologic method

Binds to structural or functional proteins, glycoproteins, or to polysaccharids,

lipids in the extracellular matrix

Diagnosis and/or prognosis

Mesenchymal tumours

1. Connective tissue

2. Muscular tissue (topic 78)

3. Vascular tissue (topic 81)

4. Hemolymphatic tissue (topic 82)

1. Benign tumours of the connective tissue

Fibroma (collagen fibres)

Myxoma (embryonic)

Lipoma (adipose tissue)

Chondroma (cartilage)

Osteoma (bone)

Osteochondroma

Fibroma

Tumour of fibroblasts

Durum („firm”) és molle („soft”) type

Frequently mixed with other tissue types (leiomyofibroma, fibroadenoma,

fibromyxoma, etc.)

Periferal odontogenic fibroma [POF] is frequent in dog’s oral cavity

(formerly epulis)

Neoplasm of periodontal ligament

Fibroblasts

Intratumoral vessel

Collagen fibres

POF

Equine sarcoid

• Non-productive bovine

papillomavirus-1 and -2 infection

• Most frequent tumour of horses

• Semimalignant tumour

• Feline sarcoid looks also like this

Myxoma

Gelatinous connective tissue, fibroblast origin

Mucin-rich stroma

Differential: edematous fibroma

Rare type (older dogs, cats)

Mostly in subcutis

Lipoma

Benign tumour of adipocytes

Very high incidence (especially dogs)

Predisposition: bitch, castrated Siamese cat

Rarely: fibrolipoma, angiolipoma

Rarely: infiltrative lipoma (semimalignant)

Horse: mesenterial lipoma (pedunculated!)

Chondroma

Benign tumour of cartilage

Mostly hyalin cartilage

Primery bone origin

Enchondroma (medullary cavity)

Ecchondroma (other locations in skeletal system – mostly plain bones)

In older dogs and sheep

Slow growth, can cause bone deformity

Often a component in canine benign mixed mammary gland

tumour (extraskeletal chondroma)

Osteoma

Neoplasm of bony tissue (compact or trabecular)

Usually soliter, affects the bones of head

Differential: reactive ossification (callus) after trauma (+

osteophyte, exostosis, enostosis, osteosclerosis, metaplasia,

osteochondroma)

Ossifying fibroma: affects horses’ jaw

Often a component in canine benign mixed

mammary gland tumour (extraskeletal osteoma)

Osteochondroma

Bony proliferation capped with cartilage, endochondral

ossification in the bone

Usually soliter, sometimes multiplex (osteochondromatosis)

Tumour or dysplasia (mostly originates from epiphyseal

layer)?

Young dogs, horses

Cat: osteochondromatosis

FeLV, FeSV role?

Differs from dogs’ and horses’ disease

Progressive growth, different localisation

2. Malignant tumours of connective tissue

Differentiated soft tissue sarcomas

Fibrosarcoma (collagen fibres)

Myxosarcoma (embryonic)

Liposarcoma (adipose tissue)

Chondrosarcoma (cartilage)

Osteosarcoma (bone)

Less differentiated/anaplastic sarcomas

Fibrosarcoma

Feline injection-site sarcoma (FISS)

Myxosarcoma

Liposarcoma

Chondrosarcoma

Osteosarcoma

Central (productive or non-productive)

Periferal (periosteal or parosteal)

Anaplastic sarcomas

Pleomorph sarcoma = anaplastic sarcoma = malignant fibrous

histiocytoma

Divergent group

Primitive myofibroblast origin?

Most frequent in dogs

Golden retriever, rottweiler

Giant cell type also exists

78. Melanocytic tumors, the

important tumors of nervous

tissue. Mixed tumors

Melanocytic tumours

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)

Melanocytoma

Epidermal, dermal or adnexal

Mostly affects dogs (vizsla!), horses (Arabian)

Aged animals

Melanoma

Malignant, agressive neoplasm

Mucocutaneous junction!!, oral cavity

Rarely (10%) on hairy skin (head, scrotum)

Mostly in dogs

Very pigmented amelanotic (grade!)

Benign muscular tumours

Rhabdomyoma

Leiomyoma

Cardial rhabdomyoma

Rhabdomyoma

Extremely rare (also is human)

Rhabdomyoblast origin (skeletal muscle)

Larynx!

Leiomyoma Much more often

Tumour of smooth muscle tissue

Dog: vagina, GI tract

Leiomyofibroma occurs (frequent)

GIST

Cardial rhabdomyoma

Mostly in pigs

Malignant muscular tumours

Rhabdomyosarcoma

Leiomyosarcoma

Cardial rhabdomyosarcoma

Rhabdomyosarcoma

Leiomyosarcoma

Cardial rhabdomyosarcoma

Tumours of nervous tissue

Neoplasms affecting older animals, therefore mostly occurs in

dogs and cats

Can be in central (CNS) and periferal (PNS) nervous system

Very tight connection between pathology and clinical history

Primery CNS tumours

Astrocytoma

Oligodendroglioma

Oligoastrocytoma

Ependymal and choroid plexus tumours

Medulloblastoma

Neuroblastoma

Meningioma

Astrocytoma

Subgroup of gliomas

Divergent group, many histotypes (diffuse or well-circumscribed)

15% of all CNS tumours

Mostly in dogs, brachycephalic breeds (sporadic in other species)

Oligodendroglioma

Oligodendrocytic origin

Well-circumscribed, but infiltrative tumour

Mostly in dogs, brachycephalic breeds (sporadic in other

species)

Mostly in frontal regions of hemispheres

Often gelatinous macroscopically

Oligoastrocytoma

Diffusely infiltrative type of glioma

Carries characteristics of astrocytoma and oligodendroglioma

Medulloblastoma

Primitive neuroectodermal tumour

Affects the cerebellum

In older dogs and cats

Meningioma

Originates from meningeal cells

Most frequent primery CNS tumour in dogs (45%) and cats (60%)

Boxer, golden retriever!

Usually soliter, well-circumscribed

Also in spinal cord, intradural (C, L-S)

Primery PNS tumours

Schwannoma (benign [periferal] nerve sheath tumour)

Neurofibroma

(Perineurioma) – very rare!

Malignant (periferal) nerve sheath tumour

Mixed tumours

Composed by more cell types

Pluripotent or totipotent stem cells

Goes through on divergent differentiation

Canine mammary gland: benign mixed tumour

neoplastic epithelial component:

• glandular, tubular: luminal epithelial cells

+myoepithelium

+mesenchymal elements: cartilage, bone, adipose tissue, etc.

Teratoma and teratocarcinoma: from totipotent stem cells (normally in

testicle, ovary, sequestred mesodermal embryonic remnants) →

both ecto-, meso- and endodermal components in the tumour (mature or

immature cells)

Thank you for the attention