How is this type of tumor diagnosed?

These tumors are typically found as either singular or multiple nodules along your cat’s abdomen during a physical exam. Other procedures are then performed to determine the type of tumor and whether it is benign or malignant.

• A common procedure to diagnose this tumor is a fine needle aspiration (FNA).
  • FNA involves taking a small needle with a syringe to suction a sample of cells directly from the tumor and place them on a microscope slide.
  • A veterinary pathologist then examines the slide under a microscope.
• In some cases, results from FNA may not be entirely clear and removal of the entire tumor may be necessary.
  • Pieces of the tumor are then examined by a veterinary pathologist under a microscope. This is called histopathology.
  • Histopathology is not only helpful in making a diagnosis but can also indicate whether it is benign or malignant and how the tumor is likely to behave.
• Given the risk of metastasis with malignant mammary tumors, your veterinarian may also recommend staging (searching for potential spread to other locations in the body).
• This may include blood work, urinalysis, radiographs (X-rays) of the lungs, and possibly an abdominal ultrasound and CT.

Lymph nodes associated with the mammary glands may be sampled by FNA, even if they seem normal.

Staging

Full staging is recommended before any treatment, given that most feline mammary tumors are malignant and stage of disease substantially impacts both treatment and prognosis.

• In addition, staging allows screening for concurrent diseases that might influence not only prognosis, but also the degree to which treatment will be tolerated.
• The staging system most commonly applied to cats with mammary tumors is adapted from the WHO staging system.
• Stage advances as the size of the primary tumor increases, from < 2 cm (stage I), to 2–3 cm (stage II), to > 3 cm (stage III).
• Regardless of tumor size, lymph node involvement also represents stage III disease, and distant metastasis constitutes stage IV disease. Evaluation of the primary tumor’s diameter is very helpful in establishing prognosis because larger tumors (> 3-cm diameter) carry a worse prognosis than smaller tumors.

Staging of Feline Mammary Tumors

The staging process should include hematologic and biochemical testing, as well as urinalysis, because most cats with mammary tumors are elderly and may have concurrent disease.

• The local/sentinel lymph nodes and the lungs are the most common sites for metastasis, although abdominal organs and other lymph nodes can also be affected.
• As such, imaging is a crucial part of staging and should include both thoracic and abdominal imaging (typically thoracic radiography or CT and abdominal ultrasonography).
• Fine-needle aspirates of local lymph nodes should also be performed because normal-sized lymph nodes do not exclude metastatic disease.
• If local lymph nodes cannot be palpated, ultrasonography can be used to direct fine-needle aspiration.