Skin Flashcards
Which of the following statements regarding skin tumors are the most accurate?
A) Merkel cell tumors are highly aggressive in the canine patient, with high rates of metastasis
B) Local invasion of apocrine gland carcinomas is very common, with more than half demonstrating invasion of the stroma
C) Trichoepitheliomas are always benign and does not invade surrounding tissues
D) Malignant pilomatricoma has not been reported in dogs
B)
Merkel is malignant in humans but usually benign in dogs. There is a malignant trichoepithelioma. Malignant pilomatricoma is rare in dogs, never reported in cats
What are the most common skin tumours in the dog?
mast cell tumour, lipoma, histiocytoma
What are the most common skin tumours in the cat?
basal cell tumour, mast cell tumours, SCC
What’s the proposed staging system for primary tumours of the ear canal?
T1 = tumour confined to the external or horizontal canal
T2 = tumour extending beyond the tympanic membrane
T3 = tumour extending beyond the middle ear/ bone destruction
What are some prognostic factors for tumours of the ear canal?
What are the three most prevalent skin tumors in cats (in order):
a. Squamous Cell Carcinoma, Basal Cell Tumor, Mast Cell Tumor
b. Basal Cell Tumor, Mast Cell Tumor, Fibrosarcoma
c. Mast Cell Tumor, Squamous Cell Carcinoma, Basal Cell Tumor
d. Basal Cell Tumor, Mast Cell Tumor, Squamous Cell Carcinoma
D
In people, basal cell carcinomas (BCCs) are thought to arise from critical mutations in the hedgehog signaling pathway. In the dog, which of the following is involved in the transcription of the canine hedgehog signaling cascade?
a. Chromosome 10 of gene GLI1
b. p53
c. p27
d. Beta-Catenin
A
You have a 7 yo MC Norweigan Elkhound that presented with several dermal masses along the neck, back, shoulders, and tail. Since there were multiple masses, surgical excision of all masses would not be feasible. As such, you elected treatment with Isotretinoin. Which of the following benign dermal masses does this dog most likely have?
a. Trichoblastoma
b. Trichoepithelioma
c. Infundibular Keratinizing Acanthoma
d. Pilomatricoma
e. Nodular Dermatofibrosis
C
Which of the following correctly ranks the following skin tumors of dogs from most to least common:
A. Lipoma, papilloma, melanoma, SCC
B. Basal cell tumor, histiocytoma, fibrosarcoma, lipoma
C. MCT, melanoma, histiocytoma, sebaceous adenocarcinoma
D. MCT, lipoma, histiocytoma, perianal gland adenoma
D
What’s a risk factor for SCC?
UV radiation, especially in light-colored cats
How does papillomavirus induce neoplastic transformation?
- can only effect terminally differentiated cells –> stimulate increased proliferation and differentiation of keratinocyte once infected
- destabilizes p53 by viral protein E6 and inhibition of pRB by viral protein E7
- disruption of p53 increases p16 protein level –> can be detected by IHC
What cancer can papillomavirus predispose dogs to?
squamous cell carcinoma
What is papillomavirus associated with in cats?
viral plaques and feline fibropapilloma (feline sarcoids)
- can progress to squamous cell carcinoma
- up to 70% of “UV Protected” SCC are positive for PPV
What does positive staining of p27 mean?
p27 is a protein important in maintaining cells in G0 – a decrease = more cell cycle
What’s the importance of Beta-catenin?
Beta catenin is responsible for normal skin homeostasis
nuclear presence of this protein = pathway activation
- aberrantly activated in formation of hair follicle tumours
What’s the role of cyclin A in SCC?
Cyclin A was present in 90% of feline SCC, 40% of canine SCC
T or F. Digit and oral melanoma are highly malignant tumours?
True
What kind of cells can be found in cytology of basal cell carcinoma?
inflammatory cells, squamous cells, sebaceous epithelial cells, melanin, and melanophages
Which dog breeds are predisposed to basal cell tumour?
Cocker Spaniel and Poodle
(although overall rare in dgos)
How does basal cell tumour look like in the dog?
plaques or nodules in the skin; alopecic, intact or ulcerated
Median age = 9y
How aggressive in basal cell tumour in the dog?
low grade malignancy
recurrence possible
no metastasis reported
How frequent is basal cell tumour in the cat?
now thought to be rare – mostly reclassified to solid-cystic apocrine ductular adenoma (60%) or trichoblastomas (40%)
- 10-20% of feline skin tumours
Where are feline basal cell tumour mostly located?
head and neck
can look like melanoma
How aggressive is basal cell tumour in the cat?
mostly benign, but malignant ones have been described thought metastatic rate appears low
What’s the treatment for basal cell tumour?
wide surgical excision = good long-term control - aim for 5-10mm
How frequent is papilloma in the dog and cat?
rare