Neoplasia
Abnormal, uncontrolled cell proliferation resulting in tumor formation. Neoplasia encompasses both benign growths and malignant cancers, and is the leading cause of death in dogs over 10 years of age.
Neoplasia (from Greek: neo- “new” + plasis “formation”) is the medical term for the process of abnormal, uncontrolled cell growth. A neoplasm — the resulting mass of abnormal tissue — is commonly called a tumor. Not all neoplasms are cancerous, but all cancers are neoplasms.
Benign vs. Malignant Neoplasia
Benign neoplasms grow locally, do not invade surrounding tissues, and do not metastasize (spread to distant organs). Examples in dogs include lipomas (fatty tumors), sebaceous adenomas, and cutaneous histiocytomas. Benign tumors can still cause problems through compression of adjacent structures.
Malignant neoplasms (cancers) invade surrounding tissues, can metastasize through blood or lymphatic vessels, and are potentially life-threatening. Common malignant neoplasms in dogs include lymphoma, hemangiosarcoma, osteosarcoma, and mast cell tumors.
Why Neoplasia Increases With Age
Cancer risk rises sharply with age in dogs. An estimated 50% of dogs over 10 years old will develop some form of cancer. The age-related increase reflects:
- Accumulated DNA damage: decades of oxidative stress, environmental carcinogen exposure, and replication errors accumulate mutations in growth-regulating genes
- Declining immune surveillance: the immune system becomes less efficient at identifying and eliminating abnormal cells (immunosenescence)
- Senescent cell accumulation: the inflammatory secretions (SASP) from senescent cells create a pro-tumorigenic microenvironment
- Telomere dysfunction: critically short telomeres can trigger chromosomal instability rather than orderly senescence
Breed Predispositions
Certain breeds carry significantly elevated cancer risk. The Golden Retriever Lifetime Study documents cancer incidence exceeding 60% in the breed. Bernese Mountain Dogs have one of the highest rates of histiocytic sarcoma. Boxers are predisposed to mast cell tumors and lymphoma.
Early Detection
The “new lump rule” is practical: any new mass in a dog over 5 years old warrants fine-needle aspirate cytology. Additional screening tools include routine bloodwork (monitoring for cytopenias, elevated calcium, liver enzyme changes), abdominal ultrasound for splenic masses, and emerging liquid biopsy technologies that detect circulating tumor DNA.