Squamous cell carcinomas in cats: clinical presentation and management
Squamous cell carcinomas in cats are neoplasms with a significant mortality rate.
Introduction
Squamous cell carcinomas in cats are malignant neoplasms that develop in the squamous epithelium, mainly impact the skin and oral cavity, and usually affect older cats (mean 10–12 years).1
They account for 15–25% of skin neoplasms in cats and are mainly found in unpigmented skin and in areas with little hair, e.g., around the pinna, eyelids and nasal planum.
Approximately 10% of squamous cell carcinomas (SCCs) appear in pigmented areas as multiple superficial lesions, variably referred to in the literature as multicentric squamous cell carcinoma in situ, bowenoid in situ carcinoma or Bowen’s disease.1,2
Moreover, SCC is the most common oral tumour in cats (60–70% of cases). It mainly affects the tongue and sublingual region, oral mucosa, lips and tonsillar region, but it can also affect the mandible and maxilla.3
A digital location, which is common in dogs, is rarer in cats; however, the possibility of a mass being a SCC solely based on its location should not be excluded. For example, two cases of squamous cell carcinoma of the anal sacs were described recently.5
Squamous cell carcinomas in cats have traditionally been considered a tumour of low metastatic potential. However, more recent studies have shown that in cases of oral presentation, the percentage of metastasis to the submandibular ganglion is at least 35.7%.4
Squamous cell carcinomas in cats: aetiopathogenesis
The aetiology of SCCs in cats is not fully understood, but it is probably multifactorial:
- If found in the skin, then exposure to solar radiation plays an important role, and white or pigmented cats with white patches are more predisposed; while Siamese (due to their characteristic pigmentation) and long-haired breeds seem to have a lower risk.2
- Moreover, exposure to tobacco smoke doubles the risk of oral squamous cell carcinoma.
- Other factors that are believed to favour the development of SCCs include the use of flea collars (multiplies the risk by a factor of 5.3), consumption of canned food (increases the risk by 3.6 times), and chronic inflammation.
Although the pathogenic mechanism is still unclear, the above factors may favour mutations in the tumour suppressor gene p53 which plays a fundamental role in the development of this cancer.1,3
Squamous cell carcinomas in cats: clinical presentation
The clinical signs depend on the location of the tumour.
- Cats with nasal squamous cell carcinomas often manifest sneezing, nasal discharge and facial deformity.
- Oral tumours course with sialorrhoea, oral bleeding, anorexia, tooth loss, weight loss and halitosis.1
- SCCs in cats often develop as a visible mass, whose appearance can include:
- A superficial crusty lesion (carcinoma in situ);
- Deep ulcerative lesions that do not heal;
- Or raised, cauliflower-like, reddish plaques.
The appearance of the lesion may change over time. Lesions on the pinnae usually show actinic changes, consisting of thickening and folding of the tips of the ears, prior to the appearance of erosions and scabs. The suspected diagnosis is sometimes based on cytology, but it is usually confirmed by excisional or incisional biopsy.1
Cutaneous SCCs are staged according to the WHO classification as:1
- Tis, a pre-invasive carcinoma (carcinoma in situ) that has not crossed the basement membrane.
- T1, tumour < 2 cm in diameter, superficial or exophytic.
- T2, tumour 2–5 cm in diameter or minimally invasive irrespective of its size.
- T3, tumour > 5 cm in diameter or subcutaneously invasive irrespective of its size.
- T4, tumour that invades other structures, such as fascia, muscle, bone or cartilage.
Treatment
Treatment options for SCCs in cats include surgery, radiation therapy, chemotherapy, plesiotherapy, electrochemotherapy, cryotherapy, photodynamic therapy and the use of nonsteroidal anti-inflammatory drugs.1-6
Furthermore, depending on tumour location, good analgesic management is important and appropriate nutritional support must be provided, probably involving the placement of a feeding tube.
Surgery is considered the treatment of choice for squamous cell carcinomas in cats. Patients with well-differentiated tumours, which can be completely removed, and no vascular/lymphatic invasion or distant metastasis have a good prognosis. However, cats with inoperable, poorly differentiated neoplasms and metastasis have a very poor prognosis. Bear in mind that not all owners agree to aggressive surgery on the nasal planum or oral cavity. In these cases, other types of treatment or multimodal management should be used to try to improve patient survival. Although SCC is not classed as a chemosensitive tumour, this treatment modality could be considered in neoplasms that are inoperable or which have metastasised at the time of diagnosis.
Conclusions
Squamous cell carcinomas are malignancies that can have a high mortality rate depending on tumour location. So, upon observing compatible lesions, at the very first visit it is extremely important to recommend cytology and/or biopsy studies to obtain an early diagnosis and, therefore, guarantee a more effective treatment. Vets must always avoid the cliché of “let’s wait and see if it grows”, but rather act quickly.
As a prophylactic measure, prolonged exposure to ultraviolet radiation should be avoided in at-risk cats; failing that, the application of protective creams on the most compromised areas of skin should be considered.1
