강아지 종양 생검·세침흡인검사 증상과 원인, 진단·치료와 관리 포인트 총정리

Complete Guide to Canine Tumor Biopsy and Fine-Needle Aspiration (FNA) — How to Distinguish Benign from Malignant

Oncology/CancerDiseasesMeongsiljang Veterinary Advisory Board

Tumor biopsies and fine-needle aspiration are key diagnostic methods for accurately determining whether a dog’s tumor is malignant. Be sure to understand these procedures for early detection and appropriate treatment.

What Are Canine Tumor Biopsy and Fine-Needle Aspiration?

A veterinarian examining a dog's tumor site

Tumor biopsy and fine-needle aspiration (FNA) are essential diagnostic procedures for accurately determining the nature of a tumor. - Fine-Needle Aspiration (FNA): This method involves inserting a thin 21–23-gauge needle into the tumor, applying negative pressure to collect internal cells, and then performing cytology to identify cell types and evaluate them against criteria for malignancy. Most dogs tolerate this procedure well even while conscious, as it causes minimal discomfort, and results can be obtained relatively quickly. - Biopsy: This procedure involves surgically removing a tissue sample for detailed histopathological analysis. For certain diseases and tumors, it is the only way to achieve a definitive diagnosis. These two methods are used complementarily, with your veterinarian selecting the most appropriate approach based on the specific characteristics of the tumor. Early diagnosis plays a crucial role in establishing an effective treatment plan and ongoing management.

Main Reasons for Tumor Biopsy

A biopsy of a dog’s tumor is performed to accurately determine the nature of the growth. If there is a high likelihood that the tumor is malignant, a biopsy is essential for early treatment. It serves as the foundation for developing a treatment plan.

Suspected cancer cells: Rapidly growing lumps or masses under the skin that do not move are more likely to be malignant.

Foreign body reaction: If a lump persists after an injury, it is important to rule out malignant metastasis.

Abnormal bleeding: Frequent bleeding from a lump may indicate tissue damage or be a sign of cancer.

Persistent pain: If the area around the lump is swollen and the dog shows significant discomfort when touched, there is a higher possibility of malignancy.

Key Symptoms and Signs

There are various symptoms that may indicate your dog needs a tumor biopsy. Early detection significantly impacts treatment outcomes, so please consider visiting a clinic immediately if you notice any of the following signs:

Rapidly growing lump: A lump that visibly increases in size within a week is highly likely to be malignant.

Skin discoloration or ulceration: The skin around the lump may become red, flaky, or develop ulcers.

Persistent pain: Your dog may react strongly when touched or show signs of pain while moving.

Weight loss and lethargy: As the tumor progresses, decreased appetite and reduced activity levels may occur.

Coughing or difficulty breathing: Tumors in the lungs or thymus can cause respiratory abnormalities.

Blood in stool or urine: These may be signs of internal organ tumors.

When to Visit the Vet Immediately

If your dog shows severe pain around the lump or if the lump has doubled in size within a day, you should visit the vet immediately. If the malignant tumor has started to metastasize, the timing of treatment is very critical.

Diagnostic Methods and Procedures

Diagnosing tumors in dogs typically involves fine-needle aspiration (FNA) and biopsy. While FNA is relatively painless, a biopsy requires removing a tissue sample and is therefore an invasive procedure that usually requires anesthesia. Your veterinarian will select the most appropriate method based on the tumor’s size, location, and characteristics. - Fine-Needle Aspiration (FNA): This method uses a thin 21–23 gauge needle to extract cells from within the tumor for cytological analysis. Because it causes minimal discomfort, it can often be performed while the dog is conscious, and results are available relatively quickly. - Biopsy: This involves surgically removing a tissue sample for detailed histopathological examination and is performed under anesthesia. It is the most reliable method when a definitive diagnosis is required. - Imaging: Ultrasound or CT scans are used to determine the tumor’s location and size. They can also guide needle placement to help collect cells from internal lesions. - Blood Tests: These evaluate the dog’s overall health and blood cell counts. If there is a risk of bleeding, clotting status is checked before sample collection.

Veterinarian performing a fine-needle aspiration

Treatment Methods and Step-by-Step Approach

The treatment of canine tumors depends on the type, location, and whether the tumor has metastasized. Veterinarians develop a comprehensive treatment plan, which is carried out in stages.

Surgical Treatment: If the tumor is localized, complete removal may be possible. A biopsy after surgery confirms whether the tumor is malignant.

Chemotherapy: Used to eliminate cancer cells when malignant tumors have metastasized. It is administered periodically.

Radiation Therapy: Effective for tumors in locations where surgery is difficult. Precise radiation destroys the tumor.

Immunotherapy: A treatment that stimulates the immune system to recognize cancer cells. This is an increasingly popular approach.

Supportive Care: Improves quality of life through pain relievers, nutritional supplements, and other supportive measures.

Home Care Points

Proper home care after your dog’s tumor treatment is crucial. Please follow your veterinarian’s instructions carefully and keep the following points in mind:

Wound Care: Keep the surgical site clean and regularly check for signs of infection.

Medication Administration: Give medications at the correct times and in the prescribed doses. Ensure no doses are missed.

Dietary Management: Provide nutritionally balanced food. If your dog has a poor appetite, offer smaller meals more frequently.

Activity Restriction: Avoid excessive exercise during the recovery period and provide a quiet, calm environment.

Regular Check-ups: Continue with regular veterinary check-ups to monitor for any signs of recurrence.

A puppy on a nutritionally balanced diet

Preventing Recurrence and Breed Precautions

Some dog breeds are known to have a higher risk of developing tumors. In particular, if a large-breed dog suddenly develops lameness or a firm bony swelling near a joint, a tumor should be suspected. Other warning signs that warrant attention include spontaneous nosebleeds, persistent diarrhea in senior dogs that does not respond to medication, and unexplained weight loss. Regular check-ups and early detection are essential to ensure these signs are not overlooked.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Which is more accurate, fine-needle aspiration or biopsy?

A biopsy is more accurate because it allows us to analyze the entire tissue sample, providing a clearer determination of whether the condition is malignant. While fine-needle aspiration is quicker and less painful, it may have lower accuracy in some cases.

Will my dog be in pain after a biopsy?

The discomfort is temporary. Your veterinarian will use anesthesia and prescribe pain relief medication. Most pets recover within one to two days.

If a tumor is malignant, is it untreatable?

No. Even malignant tumors can be effectively managed with surgery, chemotherapy, and radiation therapy if detected early. The success rate of treatment varies depending on the type and stage of the tumor.

What should I watch out for at home after a biopsy?

Keep the wound area dry, check for signs of infection daily, administer all prescribed medications as directed, and limit your pet’s activity. Contact your veterinarian immediately if you notice any unusual symptoms.

What should I do if my dog keeps licking a tumor?

This is dangerous. The wound can worsen or become infected. It is best to prevent your pet from licking the area by using a muzzle, crate, or pet care case.

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References

[1] Hostetter S.J. (2023) Oral cavity, gastrointestinal tract, and associated structures. In: Canine and Feline Cytology: A Color Atlas and Interpretation Guide, 2nd edn. Saunders Elsevier, St. Louis, pp. 287–296.

[2] Dhaliwal et al. (1998) Maxillectomy in dogs: surgical technique and postoperative complications. Veterinary Surgical Oncology, 2nd Ed.

[3] Newkirk K.M., Brannick E.M., Kusewitt D.F. (2021) Neoplasia and tumor biology. In: Pathologic Basis of Veterinary Disease, 7th edn. Mosby Elsevier, St. Louis, pp. 287–289.