Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Stage describes how far a cancer has spread: from a single tumor, to nearby lymph nodes, to distant organs. Grade describes how aggressive the cancer cells look under the microscope. Together, they help predict how a cancer will behave and guide treatment. Staging tests usually include bloodwork, imaging, and sampling of nearby lymph nodes.
Staging
Many cancers use the TNM system:
- T (tumor): size and local invasion
- N (nodes): spread to nearby lymph nodes
- M (metastasis): spread to distant organs, such as the lungs or liver
Some cancers have their own systems. Lymphoma in dogs, for example, is staged I to V based on how many lymph nodes and organs are involved, with substage “a” (feeling well) or “b” (sick).
Grading
- Determined by a pathologist examining a biopsy
- Low-grade tumors tend to grow slowly and spread less
- High-grade tumors are more aggressive
- Mast cell tumors, for example, are commonly graded as low or high grade
Staging tests
- Physical exam and lymph node palpation
- Bloodwork and urinalysis
- Chest X-rays or CT
- Abdominal ultrasound
- Needle samples of lymph nodes
- Bone marrow sampling for some cancers
Why it matters
- Early-stage, low-grade tumors may be cured with surgery alone.
- Higher stages or grades may need chemotherapy, radiation, or other treatments.
- Staging helps set realistic expectations.
More: cancer treatment options.
Sources
- Merck Veterinary Manual: Neoplasia in dogs
- Biller B, et al. 2016 AAHA Oncology Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2016
- Kiupel M, et al. Proposal of a 2-tier histologic grading system for canine cutaneous mast cell tumors. Vet Pathol. 2011
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.