Tumours are overgrowths of cells within the body. The name basal cell is an umbrella term to describe tumours which can originate from the basal cell layer of the epidermis (the outer layer of the three layers that make up the skin), hair follicles, sweat and sebaceous glands. They make up between 15-25% of all skin tumours found in cats.
Basal cell tumours are slow growing. They may be benign (basal cell tumour) or low-grade malignant (basal cell carcinoma), thankfully, 90% of basal cell tumours in cats are benign. Malignant basal cell carcinomas rarely metastisise (spread to other parts of the body).
Tumours affect middle-aged to senior cats.
There is no known definitive cause, however, some possible causes include:
Sun exposure – Basal cell tumours in humans are due to sun exposure.
Genetic predisposition – Reports are contradictory on the incidence in certain breeds with some suggesting a predisposition in Siamese, Persian and Himalayan cats.
Growths can develop on any part of the body, although are more common on the head, face, neck, and shoulders.
Benign basal cell tumour:
Firm, solitary, well-defined, hairless bumps which can range in size from 0.2 cm to 10 cm
Dark pigmentation of the lump is common
Ulceration and secondary infection can develop
Basal cell carcinoma:
Unlike benign basal cell tumours, basal cell carcinomas are often flat and ulcerated, they can spread to surrounding skin, forming new ulcers
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you including how long the tumour has been present.
It is possible to make a tentative diagnosis based on the appearance of the tumour, however, it is not possible to provide a definitive diagnosis without diagnostics. These can include:
Baseline tests – Which include complete blood count, biochemical profile and urinalysis to evaluate the overall health of your cat.
Cytology – This is a quick and non-invasive method for the veterinarian to evaluate tumours. The veterinarian will perform a fine needle aspirate to obtain cell samples. A needle removes samples from the tumour, which are then smeared in a thin layer on glass slides and looked at under a microscope.
Histopathology – If cytology shows cells a tumour, a tissue sample will be obtained for evaluation by a veterinary pathologist to determine if is malignant or benign. If the tumour is malignant, staging will be necessary.
ChestX-rays and ultrasound – To check for metastasis if the tumour is malignant.
Lymph node aspiration – For cats with malignant basal cell carcinoma.
The goal of treatment is to remove the tumour.
Surgery with a wide margin for benign tumours or a wide margin for malignant carcinomas is the mainstay of treatment for basal cell tumours.
Cryosurgery (freezing) for tumours which are less than 1 cm in diameter.
Radiotherapy as a follow up if it is not possible to remove the tumour with a wide enough margin.
It is possible for tumours to return, which will require additional surgery.
Your cat will be discharged either the day of surgery or the day after. Depending on the location, it may be necessary to wear an Elizabethan collar to prevent self-trauma of the surgery site.
The veterinarian may prescribe painkillers to relieve discomfort. Administer as directed.
Keep a close eye on the surgery site for signs of infection, which include redness, oozing, and an unpleasant odour.
It will be necessary to see the veterinarian for a follow-up 7-10 days post surgery to remove non-dissolvable stitches.