Feline fibrosarcoma or sarcoma associated with the injection site, accounts for between 6 and 12% of feline tumors It is a mesenchymal tumor in which connective tissue fibroblasts proliferate. It is a neoplasm very aggressive and with a high tendency to local recurrence. They appear as a small lump or swelling that grows rapidly, however, they do not usually metastasize to other organs.
What is feline fibrosarcoma?
Fibrosarcoma is a malignant mesenchymal tumor in which fibroblasts proliferate, cells present in connective tissue that generate collagen and are involved in the scarring. It is mesenchymal since it is a tumor of mesenchymal origin, a tissue that forms in the embryonic state of the feline and that gives rise to support and connective tissues.
Feline fibrosarcoma has a rounded, soft, or solidappearance, and can be single or multinodular. Adhesions to nearby skin layers frequently occur. It is not a painful tumor or with ulcerations, except in the final stage. It is rare for metastases to appear (arrival of cancer cells in other parts of the body), while recurrence of the tumor once removed is common.
Fibrosarcoma symptoms in cats
Feline fibrosarcoma can appear at any age. However, it is more common in middle-aged cats. At first, the lump is very small and is noticeable when petting the cat, but grows in size very quickly.
This mass may be relatively mobile and be fixed to the subcutaneous tissue and underlying musculature, with probable infiltration of surrounding structures. This makes the space between the tumor and he althy tissue poorly defined. The inoculation zone is most often the interscapular zone (between the cat's shoulders and neck). Large masses may be affected by trauma or ulcerate.
On the other hand, if metastasis appears, which mainly occurs in the lung, respiratory alterations. would appear.
Causes of fibrosarcoma in cats
In general, tumors appear as point genetic mutations. However, in the case of feline fibrosarcoma it can occur for these reasons:
- Vaccination: after a vaccination at the point of inoculation of the vaccine. Some cats develop a small inflammatory nodule at this point that disappears in two to three weeks as a side effect of vaccination. If it does not disappear, chronic inflammation can lead to the development of this tumor. This inflammation at the point of vaccine inoculation occurs more frequently in vaccines with adjuvants, which are components that are added to vaccines to improve their effectiveness. The vaccines that most frequently contain adjuvants are those for rabies and feline leukemia.
- External agents: other external agents in the subcutaneous tissue, such as microchips, lufenuron or long-acting antibiotics.
- Feline sarcoma virus: Another less common cause is that feline sarcoma virus, derived from feline leukemia virus, of give rise to this type of tumor.
Feline fibrosarcoma diagnosis
First of all, a differential diagnosis should be performed with an abscess at the injection site with ultrasound and rule out infection by feline leukemia virus from a test.
Cytology is of little use in the diagnosis, requiring Wedge incision biopsy and its pathological study. This biopsy should be performed on lumps larger than two centimeters and on those that have been present for three months after inoculation or grow during one month of inoculation.
Biopsy histology will show a significant inflammatory component, with proliferation of mononuclear cells, fibrosis, and granulation. These sarcomas are characterized by high mitosis (cell division) activity and large central necrosis (cell death).
Also X-rays should be taken, especially of the chest, to assess whether or not there are metastases in the lung or other locations.
Feline fibrosarcoma treatment
Treatment of fibrosarcoma in cats will depend on the size and location of the tumor and whether or not there is metastasis. In this way, the possible treatments would be:
- Complete removal of the tumor: the main therapy will consist of the complete removal of the tumor, it being convenient to remove all the muscles and fasciae adjacent to the tumor, due to its great infiltrative capacity. Surgical margins of at least 2 cm are required, ideally 3-5 cm lateral and deep to the tumor mass, which may include the vertebral dorsal spinous processes and the dorsal border of the scapula.
- Radiotherapy: radiotherapy can be used, being the irradiated area the location where the tumor was before the incision and it should be done when healing has begun, a week or two after surgery. The effectiveness of radiation therapy varies depending on the number of previous excisions, size before excision, and quality of the surgical excision.
- Chemotherapy: Chemotherapy can be 50-60% effective using carboplatin or doxorubicin. Feline fibrosarcomas not associated with vaccines have a lower response to chemotherapy, around 10-15%.
If there are metastases, aggressive surgery should not be performed.
Feline fibrosarcoma prognosis
The prognosis of feline fibrosarcoma is guarded, due to the high risk of recurrence. However, with a well-done surgery, chemotherapy and radiotherapy, the cat can live several more years.
Feline fibrosarcoma prevention
The incidence of this disease in cats increases the more they are vaccinated. However, the incidence of diseases and their fatal consequences is much higher than the risk of formation of this tumor, so vaccination should not be stopped.
To prevent difficulty in removing a tumor in the interscapular area, it is recommended to vaccinate cats in other locations, such as in the extremities or in the area behind the ribs. In this way, if this tumor appears in these areas, the limb can be amputated or a better removal can be achieved with the necessary margins in the case of the side.
