Derm - neoplastic skin diseases Flashcards
How are skin tumours classified?
Epithelial
Spindle cell
Round cell
Melanocytic
Metastasis to skin
What causes papilloma?
Papillomavirus - DNA virus
How do papilloma viruses grow?
Grow out of the skin - exophytic
What changes to the epithelium do papilloma cause?
Hyperplastic/keratotic squamous epithelium
Have a fibrovascular stalk
What cause is associated with squamous cell carcinoma?
UV light
Where do squamous cell carcinoma tend to affect?
Eyelids, ear tips, unpigmented thin hair areas
What changes to the epithelium do squamous cell carcinoma cause?
Invasive cords to squamous epithelium
Keratin pearls/aggregates form
Scirrhous - fibrous tissue forms around the mass
What can cause digital squamous cell carcinoma in cats?
Pulmonary metastasis
What are infundibular cysts, infundibular keratinising acanthoma and trichoblastoma examples of?
Tumours of the hair follicles
What to tumours of the hair follicles mostly present as?
Benign, slow growing masses in older animals
What is the most common tumour of the hair follicle in dogs?
Infundibular cyst
What are the features of an infundibular cyst?
Marked thickening of the epithelial lining of the hair follicle
What are the features of a keratinising acanthoma in dogs?
Keratin protrudes out of the opening of the hair follicle
Complete branching of the wall
What are some sebaceous gland masses?
Sebaceous hyperplasia
Sebaceous adenoma
Sebaceous adenocarcinoma
What is the most common sebaceous gland mass?
Sebaceous hyperplasia
What is a Sebaceous hyperplasia?
Benign proliferation of normal sebaceous glands
What is an example of a Sebaceous adenoma?
Meibomian gland adenoma
Where is a meibomian gland adenoma located?
In the eyelid
What is another name for a hepatoid gland hyperplasia?
Circumanal gland hyperplasia/adenoma
What signalment of animal are circumanal gland hyperplasia/adenoma found in?
Middle age/older intact male dogs (partially castration responsive)
What kind of tumour is more common in anal sac apocrine gland tumours?
Adenocarcinoma rather than adenoma
More likely to be malignant
What are the main features of anal sac apocrine gland tumours? What side effects do they cause?
Metastatic, infiltrative
Cause pseudo-hyperparathyroidism
Cause Paraneoplastic hypercalcaemia
What structures can mesencymal cell tumours affect?
Fat
Fibrous tissue
Muscle
Blood vessels
Bone
Cartilage
What is fibrous tissue?
Collagen - fibroblasts
What animal are fibromas mostly found in?
Cats
What is the appearance of fibromas?
Well circumscribed bundles and whorls of collagen with uniform fibroblasts
What animal are fibrosarcomas usually found in?
Dogs
Young and old cats
What differs between young and old cats with fibrosarcomas?
Young cats - multicentric fibrosarcomas from FeLV
Old cats - solitary fibrosarcomas from injection sites
What is the appearance of a fibrosarcoma on histopath?
Pleomorphic cells with mroe mitotic figures and giant cells
Rapid growth, infiltrative
Are fibrosarcomas metastatic?
No
What are sarcoids? What causes them?
Fibrous tissue tumours in horses caused by bovine papilloma virus
What is the appearance of sarcoids on histopath?
Hyperplastic epidermis
Whorls and bundles of collagen/fibroblasts
Usually low mitoses
Local infiltration
Are sarcoids metastatic?
No - local infiltration only but may recur after removal
What are histiocytic tumours?
Tumours from cells that infiltrate the skin
What is the most common dog skin tumour?
Histiocytoma
What is a histiocytoma?
Benign rapidly growing ‘strawberry button’ tumour in young dogs that can spontaneously regress
What makes up a histiocytoma?
Dendritic langerhans cells
Cytotoxic lymphocytes infiltrate at the base
Will histiocytomas recur after excision?
No
What animal do mast cell tumours affect?
Dogs - bad, more common
Cats - benign, rarely metastasise
Do mast cell tumours metastasise?
Yes - local infiltration and metastasis to local lymph nodes
What is the appearance of mast cells on histopath?
A sheet of mast cells with varying differentiation and depth of infiltration
Will see eosinophils (pink) and lymphoid aggregates
What can mast cells cause?
Paraneoplastic effects - histamine
What are the two forms of melanocytic tumours?
Melanocytoma - benign
Malignant melanoma
What animal is a benign dermal melanomas found in?
Dogs
What do benign dermal melanomas look like grossly?
Pigmented solitary nodule of haired skin
What do benign dermal melanomas look like on histopath?
Contain dermal infiltrate and epidermal nests with junctional activity
Melanophages present
What animal are malignant melanomas found in?
Dogs
Where are malignant melanomas found?
Oral
Digital
Scrotal
Can malignant melanomas metastasise?
Yes - not always a poor prognosis but may metastasise to local lymph nodes or lungs
What do malignant melanomas look like on histopath?
Hard to distinguish from benign ones
but pleomorphic, mitoses
Invasiveness
Not more pigmented - may be amelanotic
What animal gets melanomas quite a lot?
Horses - especially grey ones older than 6
What is it called when horses have multiple melanomas?
Melanomatosis
Are equine melanomas malignant?
They can be, but they are slow growing
