Incisional Biopsy vs. Excisional Biopsy: A Comparison

ImmunityQ&AMeongsiljang Veterinary Advisory Board

We’ve put together a clear overview of the differences between incisional and excisional biopsies, when each method is chosen, and what to expect during recovery, including important aftercare tips.

How Do Incisional and Excisional Biopsies Differ?

An illustration of a veterinarian examining a lump on a dog's shoulder.

An incisional biopsy is a diagnostic test in which only a portion of the tumor is removed and examined under a microscope. The key consideration is the selection criteria. If the tumor is large or if its nature needs to be confirmed before surgery, an incisional biopsy is recommended. For small lumps that can be completely removed, an excisional biopsy is advised. The method varies significantly depending on the type and location of the lesion, so it is essential to have a thorough consultation with your veterinarian.

Understanding the Basic Concepts of Both Procedures

An incisional biopsy involves removing only a small portion of a tumor for pathological examination. Since the entire tumor is left intact, this approach is more akin to a diagnostic sampling. In contrast, an excisional biopsy involves removing the entire tumor in one piece, with the excised tissue sent directly to the pathology lab. This method serves as both treatment and diagnosis. Veterinary surgical textbooks distinguish between these two approaches based on the size of the lesion and the suspected level of malignancy.

Key Comparison: Incisional vs. Excisional Biopsy

Item	Incisional biopsy	Excisional biopsy
Purpose	Diagnosis only	Diagnosis + treatment
Amount of tissue sampled	A portion	The entire mass
Suitable cases	Large tumors, ambiguous location	Small with clear margins
Surgical scale	Small	Moderate to large
Type of anesthesia	Local/sedation possible	General anesthesia
Recovery period	Relatively short	Relatively long
When malignancy is suspected	First choice	After surgical planning

The actual choice is made by the veterinarian based on the tumor size, location, and suspected disease.

When Should You Choose an Incisional Biopsy?

Incisional biopsy is the preferred initial approach for large tumors, lesions in delicate locations, and masses suspected of being malignant. This is especially true for areas where extensive removal could compromise function, such as the oral cavity, perianal region, or near joints. Additionally, for tumors like mast cell tumors and soft tissue sarcomas, where malignancy dictates the extent of surgical resection, it is essential to confirm the nature of the lesion first before formulating a surgical plan. Inappropriate excision can lead to the need for additional surgeries or worsen the prognosis.

A veterinarian taking a tissue sample from a large tumor on a dog's leg

When Is an Excisional Biopsy Better?

Excisional biopsy is particularly useful for small, well-defined lumps, lesions suspected to be benign, or areas where complete removal won't impair function. Common examples include subcutaneous lipomas and skin papillomas, which are likely benign. By removing the entire tumor along with a portion of normal skin in an elliptical shape, diagnosis and treatment can be completed in one step, reducing the burden on pet owners. However, for firm nodules or tumors, it's safer to first perform a fine-needle aspiration test to rule out locally invasive tumors like mast cell tumors before removal. If malignancy is suspected, it's essential to remove the tumor with adequate margins to prevent recurrence.

Don’t Rush Into Surgical Excision

Just because you feel a lump doesn’t mean you should immediately proceed to surgical excision and biopsy. For locally invasive, malignant tumors such as mast cell tumors or soft tissue sarcomas, complete removal of the surrounding normal tissue (at least down to the next fascial layer) is necessary for a potential cure. If the excision is too narrow, cancer cells may remain at the surgical margins, leading to recurrence. This often necessitates a wider re-operation, which increases the wound size, places greater burden on the pet owner, and can worsen the prognosis. Therefore, for most firm nodules, we first perform a fine-needle aspiration to check for tumors like mast cell tumors before excision. For larger or rapidly growing lesions, we determine the nature of the mass through an incisional biopsy before planning the surgery.

How Does Pre- and Post-Procedure Care Differ?

An incisional biopsy involves removing only a small portion of the lesion, resulting in a smaller suture site and relatively faster recovery. It is often performed under light sedation and local anesthesia, allowing for same-day discharge. In contrast, an excisional biopsy requires the removal of the tumor along with surrounding healthy tissue, necessitating general anesthesia, a larger suture area, and a longer recovery period. The time required for suture removal and healing varies depending on the size and location of the lesion, so please follow your veterinarian’s specific instructions. In both cases, it is essential to keep an Elizabethan collar on to prevent licking, restrict physical activity, and keep the wound site dry. Contact the clinic immediately if you notice bleeding, swelling, or warmth at the site.

A puppy recovering at home while wearing a neck brace

How Long Does It Take to Get Pathology Results?

The removed tissue is fixed and processed, then sent to a pathology lab—ideally one with an experienced board-certified pathologist. The time required for results varies depending on the type of test, and additional procedures such as immunohistochemistry (IHC) may further extend the turnaround time. The pathology report will include the precise tissue identification, tumor grade, and surgical margin assessment. To ensure accurate interpretation, it is helpful to submit the specimen along with signalment, medical history, and a list of differential diagnoses, as well as clear orientation markers to identify the margins. If cancer cells are present at the surgical margins, additional surgery, radiation therapy, or chemotherapy may be necessary. Always discuss the results in person with your veterinarian.

Important Checks Before Biopsy in These Situations

If your cat has a blood clotting disorder or is elderly and at higher risk for anesthesia complications, preoperative blood tests and a cardiac evaluation are essential. Additionally, if your cat has a compromised immune system due to conditions like diabetes or Cushing’s syndrome, the risk of postoperative infection increases, so an antibiotic plan should be established in advance. Because cats can rarely develop injection-site sarcomas, the choice of sampling site must be carefully considered. If your cat has any of these underlying conditions, please be sure to share all current medications and past medical history with your veterinarian.

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

What’s the difference between a fine-needle aspiration (FNA) and a biopsy?

Fine-needle aspiration is a simple test that uses a thin needle to extract just a few cells. It can usually be performed without anesthesia or with only local anesthesia, but it has limitations because it doesn’t allow us to examine the tissue structure (architecture). A biopsy, on the other hand, involves removing a piece of tissue so we can analyze its structure, leading to a more accurate diagnosis, but it requires sedation or general anesthesia.

Is it true that a biopsy can cause cancer cells to spread?

In most cases, there is rarely any clinically significant spread. In fact, performing surgery without an accurate diagnosis greatly increases the risk of recurrence and the need for additional surgery. Veterinary surgical textbooks also emphasize that setting the appropriate surgical margins after a biopsy is more critical for prognosis.

How much does a biopsy cost?

Costs vary widely depending on the clinic, location, and tumor size, so it’s difficult to provide a specific figure. While an incisional biopsy is relatively straightforward, there’s an additional fee for the pathology analysis. An excisional biopsy, on the other hand, can vary significantly in cost depending on the scope of the surgery. For an accurate estimate, it’s best to consult directly with your veterinarian.

If the test results are positive, is additional treatment not necessary?

Even if a growth is benign, removal is recommended if it is enlarging or located in an area prone to repeated irritation. Additionally, depending on the histological characteristics, some benign lesions require ongoing monitoring, so it’s important to follow your veterinarian’s individualized assessment.

When can my pet bathe after a biopsy?

You can start bathing your pet once the sutures are removed and the wound has fully healed. Recovery time varies depending on the size and location of the wound, so please follow the timeline provided by your veterinarian. Until then, avoid getting the area wet to reduce the risk of infection; instead, clean it gently with wet wipes or spot-cleaning methods.

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References

[1] Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition, Chapter 9: Biopsy Principles

[2] Veterinary Surgery: Small Animal, 2nd Edition, Tobias & Johnston, Chapter 23: Surgical Oncology

[3] BSAVA Manual of Canine and Feline Oncology, 3rd Edition, Chapter 6: Diagnostic Techniques