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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