Surgery still remains one of the most effective options for the treatment of solid malignancies in dogs and cats. A wide excision
either alone or in combination with adjuvant radiation therapy can be "curative" for malignancies that are locally invasive.
However, in order to optimize the results of surgery, there are a number of issues that need to be addressed for each patient,
such as pre-surgical biopsies, pre-surgical imaging, surgical technique, biopsy submission and post-operative adjuvant therapy.
To biopsy or not to biopsy
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Benign tumors can have a similar gross appearance to those that are malignant but have a completely different biologic behavior.
Features of malignancy include local invasion and the potential for metastasis, both of which can significantly change the
treatment plan as well as the prognosis. Locally invasive tumors such as soft-tissue sarcomas will require a much more aggressive
resection, as well as adjuvant radiation therapy. Tumors that have a high metastatic potential may require adjuvant chemotherapy
as well. In addition, systemic cancers can present with localized lesions and may best be treated with chemotherapy and/or
other systemic therapies. Some owners may be less inclined to pursue treatment for those tumors that have a poor prognosis
or that would require radiation therapy and/or chemotherapy following surgery. Being able to advise owners in regards to the
extent of surgery and the potential for adjuvant therapies can help avoid unpleasant surprises.
All tumors should be considered potentially malignant. A pre-surgical diagnosis via aspirate or an incisional biopsy is highly
recommended in most cases prior to definitive excision. Exceptions to this rule would be when the biopsy procedure is as risky
as a definitive surgery or if the biopsy procedure would potentially jeopardize the chances of a successful surgical excision.
From time to time there are lesions that cannot be definitively diagnosed via cytology or an incisional biopsy due to large
areas of necrosis or inflammation. In these cases, an excisional biopsy may be required for a definitive diagnosis.
Round-cell tumors and carcinomas generally exfoliate well, so cytology is generally adequate in making a diagnosis for these
tumors (Photos 1 and 2). Sarcomas do not always exfoliate well so an incisional biopsy may be required to diagnosis these
tumors (Photo 3). If there is significant inflammation within a tumor, it may not be possible to determine if it is malignant
or benign, given that reactive cells can have features that are suggestive of malignancy (Photo 4). There is the potential
that lesions that appear to be benign on cytology are found to be malignant once removed. A common example of this is a mammary-gland
tumor, so removal of any mammary mass is recommended regardless of the cytology results. Tumors that are growing rapidly or
changing in appearance also should be removed despite a benign-appearing cytology.
Bone aspirates are becoming increasingly more useful in the diagnosis of lytic and proliferative bone lesions. An aspirate
is less invasive, less painful, can be done on an outpatient basis and has a lower risk of fracture. In most cases, the only
equipment required for an aspirate would be a 19G or 20G needle, a 10 cc syringe and a local anesthetic. Given the significant
lysis associated with most bone lesions, it is not difficult to find a soft area for an aspirate. Ultrasound can be used to
find a weak area in the cortex if there is still healthy bone present.
Bone cytology appears to have a high specificity for bone neoplasia, meaning that if a diagnosis of a malignancy is made,
the diagnosis is likely to be accurate. However, if the sample is non-diagnostic or yields a reactive process, one should
still consider the potential for neoplasia. If neoplasia is still suspected, then an alternative method of biopsy should be
considered. 
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