A lump on your cat: records and assessment

Edited by MaxTeng · Educational content, not reviewed by a veterinarian · 2026-10-26

Appearance cannot establish benignity. A veterinarian chooses sampling to suit the lesion and any surgical plan.

Describe, do not diagnose

Arrange assessment for a new or changing lump. Mobility, softness or lack of pain cannot prove it harmless. Do not squeeze, puncture or label it from a photograph.

Sampling has limits

FNA collects cells; biopsy supplies tissue information. A sample may be inconclusive, and one method does not suit every lump. Discuss the question each test can answer and any later surgery.

Injection-site 3-2-1 rule

The 2020 AAHA/AAFP guideline calls for biopsy assessment if an injection-site mass persists for 3 months, exceeds 2 cm, or grows 1 month after injection. Any one criterion matters. This is not a reason to delay contacting the vet or a rule that excludes other tumors.

Bring a lump map

Record onset, location, comparable photos and measurements obtained without pressure, changes, skin damage and injection history. Keep different lumps separate. Severe bleeding, collapse or breathing difficulty needs immediate contact.