DIAGNOSIS

Surgical oncology involves the surgical management of benign tumors and malignant cancers. The treatment of animals with cancer is well-established, and continues to be a growing field as improvements in preventive medicine and diets have resulted in our pets living longer and longer. Cancer is now the leading cause of death in older cats and dogs, and hence there is a need for everyone, from owners to family veterinarians to specialists, to be aware of the options available for the diagnosis and treatment of animals with benign tumors and malignant cancers. There are some important considerations when dealing with masses in animals, including preoperative biopsy, surgical margins, and histopathologic features of the tumor (such as tumor type, histologic grade, and histologic margins). 

DIAGNOSIS

A biopsy is often required prior to surgery to determine the definitive diagnosis and hence the need for additional diagnostic tests, to plan the surgical approach, and to provide information on expected outcome and prognosis. There are two basic approaches to biopsies: 1. Biopsy every mass prior to treatment; or 2. Biopsy when the results of the biopsy will change either the recommended treatment options (ie, different surgical approach or treatment modality other than surgery such as radiation therapy) or an owner's willingness to treat. This is an individual preference, but I personally subscribe to the more pragmatic second approach. There are four basic types of biopsies: fine-needle aspirate, needle-core biopsy, incisional biopsy, or excisional biopsy.

A fine-needle aspirate is easy to perform and does not require sedation or anesthesia. Fine-needle aspirate cytology will provide basic information on the tumor type (ie, epithelial, spindle, or round cell) and also rules out other possibilities such as infections. A fine-needle aspirate is cost-effective, the results can either be obtained in-house or within 2 days if submitted to a pathologist, and there is minimal risk of complications; however, cytology from a fine-needle aspirate is not necessarily definitive and non-diagnostic results are more likely.

Needle-core biopsies are usually performed for either bone lesions or for ultrasound-guided biopsies of internal organs.

Incisional biopsies are the preferred biopsy technique if a fine-needle aspirate is non-diagnostic. An incisional biopsy consists of collecting a wedge or punch of tissue from the mass. Sedation is often required to perform an incisional biopsy and typically we get results back from the pathologist in 5-7 days. While there is a greater risk of complications than a fine-needle aspirate, these risks are still low. The advantage of an incisional biopsy is that a tissue sample will have a greater likelihood of being representative than a fine-needle aspirate; however, a mis-diagnosis or a correct diagnosis but incorrect histologic grading are still possible.

Excisional biopsies are commonly performed, but rarely indicated. Excisional biopsies are removal of the entire mass without a knowledge of the tumor type or the required margins. There is a higher risk of incomplete excision and hence further treatment, such as surgery or radiation therapy, is more likely with the associated increase in both morbidity and costs.

Last updated on 6th March 2017