Dr Anthony Zambelli - Inanda Veterinary Hospital
Squamous Cell Carcinoma in Dogs and Cats
Any tumour growing within ( dermal ), on ( epidermal ) or even under the skin ( subdermal ) should be considered a skin tumour . Some skin tumours are benign ( i . e ., slow-growing , completely curable with complete resection and don ’ t spread ) while others are malignant ( faster growing , invasive , sometimes incurable , and may spread to other organs ). In order to classify what type of tumour you are dealing with , you will need to make a fine needle aspirate or take a biopsy A biopsy can either be incisional or excisional . Whichever course is taken , a microscopic diagnosis must always , always be obtained .
No two tumours of the same kind look the same , but very different cancers can appear similar When tumours are inflamed or infected , the underlying pathology can be masked . This information is very important . If it ’ s a cytological or incisional , this information can help guide you as the best approach to cure not only the obvious lump but also manage the precancerous lesions that surround the obvious tumour . Not all skin tumours are best removed surgically ! Only very small ( 1 – 2 cm on the body or neck , and < 1 cm elsewhere ) should be removed by excision .
Many clients and vets try to economise by removing small lumps instead of taking the extra step – this can drastically alter prognosis , by spreading tumour cells .
Although theoretically any tumour can occur in the skin , we classically think of just a few types when we say “ skin cancer ” – squamous cell carcinomas ( SCC ), melanomas , haemangiosarcomas ( HSA ) and mast cell tumours ( MCT ).
Actinic Keratosis Actinic keratosis ( AK ), also known as solar keratosis or senile keratosis , is a very common lesion occurring in susceptible humans as a result of prolonged and repeated solar exposures . The action of ultraviolet radiant energy , principally UVB , results in damage to the keratinocytes and produces single or multiple , discrete , dry , rough , adherent scaly lesions . These premalignant lesions may , in time , progress to squamous cell carcinomas .
This is very important as a warning sign and should be the first thing you teach clients about . A couple of veterinary-specific manifestations of AK are the “ comedones ” or “ blackheads ” seen on cat ’ s noses ( fig 1 ) and dogs ’ ventra . These lesions can be managed with protection , ( fig 2 ) imiquimod or Photodynamic Therapy ( PDT ). More on these modalities later .
Squamous Cell Carcinomas Squamous Cell Carcinomas are the “ classical ” skin tumours , caused primarily by long-term to exposure to UV-B radiation . The animals most afflicted white or part-white cats and dogs . Bull Terriers , Staffies , Pit Bulls , Bulldogs and Jack Russells are amongst the dog breeds most often affected . These “ ex-British ” breeds enjoy our long , glorious South African summer sun , and “ tan ” day after day .
UV-B radiation damages DNA and this damage is cumulative and only partially repairable or reversible . Squamous cell carcinomas can look like nothing more than non-healing crusts , pimples or scabs , or they can form large , raised , ulcerating plaques . vet360
Issue 06 | FEBRUARY 2017 | 20