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Also Known As: '''''SCC'''''
[[Image:cowpap1.gif|right|thumb|100px|<small><center>Papilloma and Squamous Cell Carninoma of Epiglottis (Courtesy of Alun Williams (RVC))</center></small>]]
==Introduction==
[[Image:oral squamous cell carcinoma.jpg|right|thumb|200px|<center>'''Oral squamous cell carcinoma'''. Courtesy of T. Scase</center>]]
'''Squamous cell carcinomas (SCC)''' are '''malignant''' tumours commonly seen in the cat, dog, horse and cow. They are most likely to develop in '''non-pigmented areas''' of the skin as there is a known association between their development and exposure to '''UV light'''. The tumours are normally '''slow to metastasize''' but may be locally invasive.
There are two forms of the neoplasm:
* '''Proliferative''' — cauliflower-like lesions
* '''Ulcerative''' — ulcerative lesions
Histologially, the tumours are formed from '''epidermal cells''' with varying degrees of '''squamous cell differentiation'''.
===Cat===
[[File:Feline actinic SCC.JPG|thumb|150px|right|'''Cat with actinic keratoses and eyelid SCC''' (Wikimedia Commons)]]
'''Cutaneous''' squamous cell carcinomas are common in '''white cats''', especially on the '''tips of the pinnae''', '''nasal planum''' and '''eyelid'''. '''Multiple''' tumours may develop '''simultaneously''' as the tissue has been exposed to the same level of ultraviolet damage. Often the appearance of '''acinitic keratosis''' precedes the appearance of the tumour. The lesions are normally '''crusted''', '''ulcerative''' and '''progress''' over time. They may begin very small and are commonly mistaken for cat scratches, therefore it is essential that any 'scratch' that fail to heal is treated with suspicion and '''biopsied'''. Ideal treatment is radical '''excision'''. In the case of pinna SCC's, pinnectomy is indicated.
SCC of the '''nasal cavity''' are reported. These normally originate from the nasal '''vestibule''' and cause clinical signs associated with airway obstruction and tissue necrosis.
Squamous cell carcinomas of the [[Oesophagus - Anatomy & Physiology|oesophagus]] are most notably seen in the cat, where the tumour tends to '''infiltrate''' around the oesophageal wall resulting in a “'''ring carcinoma'''”. The affected cat has progressive '''difficulty in eating''' and [[Deglutition|swallowing]]. Oesophageal SCC forms part of [[Upper Alimentary Tract Carcinoma Complex|upper alimentary tract carcinoma complex]].
===Dog===
'''Cutaneous''' SCC's are common in '''white breeds''' of dog such as the Boxer, Dalmation and English Bull Terrier.
===Horse===
'''Cutaneous''' SCC's are the second most common neoplasms in the horse. Contact with '''penile smegma''' is thought to be an a predisposing cause. They are most commonly located in the '''penile''' or '''clitoral''' regions and on '''non-pigmented''' skin. Lesions are '''progressive''' and potentially '''locally invasive'''. They may be '''ulcerative''' or '''proliferative''' and '''secondary infection''' is often present, producing a foul odour. Complete '''surgical excision''' is the gold standard treatment, but '''adjuncts''' may be required. Masses located around the eye may need prompt specialist treatment to save the eye.
SCC of the '''stomach''' is the most common gastric tumour in the horse. It has the appearance of a large '''cauliflower-like mass''' and affects the '''pars oesophagea'''. It metastasises and spreads '''transcoelomically'''.
Rarely SCC can form in the '''nasal cavity''' of the horse. These originate from the '''maxillary sinus''' and cause '''facial distortion''', '''tissue necrosis''' and '''airway obstruction'''. A '''serosanginous''' or '''mucopurulent''', '''odorous nasal discharge''' may be present.
===Cow===
As mentioned, squamous cell carcinomas are most likely to develop on '''non-pigmented areas of skin''' such as the '''eyelids'''. Additionally, there is thought to be an association between the '''ingestion of bracken fern carcinogens''' and the '''malignant transformation of papillomas''' to squamous cell carcinomas in cattle.
Squamous cell carcinomas of the [[Oropharynx - Anatomy & Physiology|oropharynx]] in cattle are commonly seen as part of an [[Upper Alimentary Tract Carcinoma Complex|upper alimentary tract carcinoma complex]].
==Diagnosis==
[[File:Well differentiated squamous cell carcinoma.jpg|thumb|right|200px|'''Well differentiated squamous cell carcinoma''' (Wikimedia Commons)]]
FNA's should be performed as a first line diagnostic test on any suspicious mass. '''Cytology''' may show:
* Pleomorphic epithelial cells - these have a variable appearance from benign keratinized mature squames to epithelial cells with anisocytosis, basophilic cytoplasm and extensive vacuolation.
* Binucleate cells, chromatin clumping and prominent nucleoli may be present
A '''biopsy''' should always be performed to confirm diagnosis.
'''Histopathological''' examination of a biopsy of the mass should reveal:
* Irregular cords or masses of epidermal cells entering the dermis
* Keratin pearls
* High mitotic rate
* Large nuclei with prominent nucleoli
* Central necrosis accompanied by high neutrophil numbers
==Treatment==
Dependant on the site of neoplasia, treatment may involve '''debaulking/complete excisional surgery''', '''radiotherapy''', '''cryosurgery''', '''photodynamic therapy''' and '''hyperthermia'''. However '''complete surgical excision is the ideal'''.
Although the metastatic rate of these tumours is normally slow, '''screening''' should be performed prior to the start of treatment. This involves '''radiography of the thorax''' and '''fine needle aspiration of local lymph nodes'''.
==Prognosis==
[[Image:cowpap1.gif|right|thumb|100px|<center>'''Papilloma and SCC of Epiglottis''' (Courtesy of Alun Williams (RVC))</center>]]
The '''smaller''' the tumour is identification, the better the chance of successful removal and a '''good prognosis'''. As mentioned, these tumours are often locally invasive but '''slow to metastasise''', however the level of malignancy and therefore prognosis is often related to the '''location''' of the neoplasm. Those arising over the '''tonsil''' (squamous carcinoma of the tonsil or tonsillar carcinoma) are '''very malignant''', invading adjacent tissues and metastasising early. Squamous carcinomas of the '''tongue''' (especially in '''cats''') can also behave in a '''very malignant''' fashion. Those at more '''rostral''' sites, e.g. on the incisor gingivae, are '''less likely to metastasize''' early although they may be locally aggressive. They should be [[Neoplasia - Pathology#Tumour Grading and Staging|staged]] according to the '''World Health Organisation (WHO) system'''.
==Prevention==
Squamous cell carcinomas can be prevented by '''protecting the skin from ultraviolet light'''. This may be achieved using '''sunblocks''' or by keeping the animals '''indoors''' or in the '''shade'''. This is rarely practicable.
{{Learning
|Vetstream = [https://www.vetstream.com/canis/search?s=squamouscell Squamous Cell Carcinoma]
|flashcards = [[Cytology Q&A 14]]
}}
{{Chapter}}
{{Mansonchapter
|chapterlink = http://www.mansonpublishing.co.uk/book-images/9781840760491_sample.pdf
|chaptername = Squamous Cell Carcinoma
|book = Sheep Medicine
|author = Philip R. Scott
|isbn = 9781840761498
}}
==References==
Bond, Hendricks, Loeffler (2009) '''Veterinary Dermatology''' RVC Intergrated BVetMed Course, ''Royal Veterinary College''
Freeman, KP (2007) '''Self-Assessment Colour Review of Veterinary Cytology - Dog, Cat, Horse and Cow''' ''Manson''
Murphy, S (2006) '''Skin neoplasia in small animals 1. Principles of diagnosis and management''' ''In Practice 2006 28: 266-27''
Murphy, S (2006) '''Skin neoplasia in small animals 2. Common feline tumours''' ''In Practice 2006 28: 320-32''
Quinn, G (2003) '''Skin tumours in the horse: clinical presentation and management''' ''In Practice 2003 25: 476-48''
{{review}}
{{OpenPages}}
[[Category:Nasal Cavity - Hyperplastic/Neoplastic Pathology]]
[[Category:Oral_Cavity_-_Proliferative_Pathology]]
[[Category:Oral_Cavity_-_Proliferative_Pathology]]
[[Category:Oropharynx_-_Pathology]]
[[Category:Oropharynx_-_Pathology]]
[[Category:Oesophagus_-_Pathology]]
[[Category:Oesophagus_-_Pathology]]
[[Category:Forestomach_-_Proliferative_Pathology]]
[[Category:Forestomach_-_Proliferative_Pathology]]
[[Category:Stomach_and_Abomasum_-_Proliferative_Pathology]]
[[Category:Respiratory System - Hyperplastic/Neoplastic Pathology]]
[[Category:Neoplasia]]
[[Category:Expert Review]]