What is a basal cell tumour?
A basal cell tumour is a slow-growing tumour that originates from the basal layer, which is the innermost layer of the epidermis. These tumours make up between 15-25% of all skin tumours found in cats and are most common in middle-aged to senior cats. There is an increased incidence in Persian and Himalayan breeds.
Basal cell tumours may be benign (basal cell tumour) or low-grade malignant (basal cell carcinoma). The majority of feline basal cell tumours are benign and malignant basal cell carcinomas rarely metastasise (spread to other parts of the body).
There is no known definitive cause; however, some possible causes include:
Sun exposure – Basal cell tumours in humans are due to sun exposure.
Growths can develop on any part of the body, although they 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
The 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 – 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 it is malignant or benign. If the tumour is malignant, staging will be necessary.
- Chest x-rays and ultrasound – To check for metastasis if the tumour is malignant.
- Lymph node aspiration – For cats with malignant basal cell carcinoma.
- Surgery: Surgical excision with a wide margin for benign and malignant carcinomas is the mainstay of treatment for basal cell tumours.
- Cryosurgery (freezing): A for tumours that 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.
Tumours can 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.
The prognosis for cats with a basal cell tumour is excellent and most cats will make a complete recovery.