Given the myriad factors that influence assessment and reporting of surgical margins, it stands to reason that surgical oncologists need to collaborate with pathologists to standardize margin reporting and continue to assess the most predictive prognostic factors within each specific tumor type. It may be that the distance method is better for predicting recurrence in one type or grade of tumor, whereas in a different tumor type, the qualitative method may be most predictive. It is imperative that surgeons understand the limits and advantages of various methods of tissue sectioning and margin interpretation, and continue to develop new means of assessing biological aggressiveness. A one‐size‐fits‐all approach is no longer the best medicine.
Palliative and Cytoreductive Surgery
The decision to perform a palliative or cytoreductive surgery is often a difficult one, and the surgeon needs to educate the client and referring veterinarian about the risks and benefits of such surgery. Piecemeal removal (debulking) of a mass should generally only be performed when the mass is physically causing obstruction or function issues. There is little advantage to debulking otherwise unless the removal results in only microscopic amounts of disease left behind. Palliation of symptoms caused by obstructive masses by removing most of or portions of large masses can temporarily improve quality of life in some cases. This should be performed only when necessary as excessive bleeding can often occur and dehiscence is very common.
Postoperative Considerations
Tissue Marking
As discussed above, following an excisional biopsy, the surgical margins of the mass should be clearly indicated in some way so that the histopathologist can accurately evaluate the mass for complete excision. Several methods have been proposed to do this including specialized sectioning techniques, suture markers, inking, and the submission of adjacent tissue as a separate sample (Rochat et al. 1992; Mann and Pace 1993; Seitz et al. 1995). Inappropriate sectioning can result in neoplastic cells being noted at the cut margin and a false positive result can occur. Sutures can be used to mark a particular area of interest or for tumor orientation, but sutures need to be removed before sectioning to prevent microscopic artifact (Mann and Pace 1993). A sample of tissue surrounding the surgical wound can also be submitted for evaluation. However, this increases the size of the wound bed and added expense may be seen due to the submission of extra biopsy samples.
In general, the marking of tumor margins with inks or dyes is recommended. Several types of inks and dyes have been evaluated including merbromin, laundry bluing, India ink, alcian blue, typists’ correction fluid, commercial acrylic pigments, and artists’ pigment in acetone (Rochat et al. 1992; Mann and Pace 1993; Seitz et al. 1995; Chiam et al. 2003). Alcian blue has been shown to be the best marking material; however, India ink and commercial kits (Davidson Marking System, IMEB Inc., San Diego, CA) are reasonable alternatives (Seitz et al. 1995). One of the benefits of the commercial kits is that multiple colors are provided. When using these kits, all the margins can be marked in different colors, but at a minimum, the lateral margin can be marked in one color and the deep margin in a different color. Yellow, black, and blue colors are considered the best to use while red, violet, and green are less ideal (Seitz et al. 1995; Milovancev et al. 2013).
Guidelines for Fixation of Surgical Tissue Specimens
Small biopsy samples should be placed in fixative immediately to prevent drying of the sample. Early fixation will initiate changes in the sample that will prevent autolysis and bacterial alteration of the sample (Stevens et al. 1974). In large biopsy submissions, the sample should be sliced evenly to allow for more complete fixation (Dernell and Withrow 1998; Ehrhart and Powers 2007). However, when slicing a large specimen, care should be taken not to slice through the surgical margins but rather leave those untouched. Therefore, the slicing is done through the skin into the tumor for cutaneous or subcutaneous tumors. Many fixatives including formalin, Bouin’s fluid, chilled isopentane, Zenker’s fluid, and glutaraldehyde have been described in veterinary medicine (Osborne 1974; Stevens et al. 1974), but in general, 10% buffered formalin is sufficient for almost all biopsies. A biopsy sample should be fixed in formalin in a 1:10 solution of tissue to formalin (Ehrhart and Withrow 2007).
Frozen Sections
The use of frozen sections is common in human medicine (Kaufman et al. 1986; Lessells and Simpson 1976). Frozen sections generate an accurate diagnosis in greater than 97% of human biopsy samples (Lessells and Simpson 1976; Kaufman et al. 1986). The process requires highly trained personnel and equipment specific to the procedure, and thus, veterinary facilities that have the capability are limited (Ehrhart 1998). In one veterinary study, the accuracy of frozen sections in determining a specific diagnosis was 83% (Whitehair et al. 1993). In that same study, frozen sections were able to make a determination between neoplastic and nonneoplastic diseases in 93% of cases (Whitehair et al. 1993).
Wound Healing
The veterinary oncologic patient has several risk factors that may increase the frequency of complications associated with wound healing (Cornell and Waters 1995). Nutritional compromise and concomitant disease can be treated to improve the outcome of wound healing, but other factors like tumor type and completeness of surgical excision have to be considered as well. Neoadjuvant/adjuvant therapies such as chemotherapy, radiotherapy, and antiangiogenic medications have also been documented to impair wound healing (Devereux et al. 1979; Cornell and Waters 1995; te Velde et al. 2002; Séguin et al. 2005) (see Chapter 2).
Proper surgical techniques, as described above, can be employed to decrease the chance of wound complications. Regular communication with the patient’s agent both before and after surgery will help to preemptively prepare for complications or aid in rapid identification and intervention when complications arise. Prevention of self‐trauma should be routinely discussed with the owner and methods of prevention such as bandaging or having the patient wear an Elizabethan collar should be included in the postoperative care.
Adjuvant Therapy
The time to discuss the potential need for adjuvant therapy in a tumor patient is prior to any surgical intervention. This allows owners to make informed choices and to better prepare for the financial burden, time required, and potential complications associated with adjuvant therapy. Failing to properly prepare the client for these additional treatments and the benefits and challenges unique to each one may leave the patient’s agent feeling overwhelmed, underinformed and may expose the patient to unnecessary morbidity or delay in treatment.
Chemotherapy in the adjuvant setting is generally administered after wound healing has been completed. Experimentally, it has been shown that administering certain types of chemotherapy before or at the same time as surgery may retard wound healing (Shamberger et al. 1981; de Roy van Zuidewijn et al. 1986; Lawrence et al. 1986a, b) (see also Chapter 2). By the time a patient is ready for suture/staple removal, a wound is generally healed sufficiently, and chemotherapy may be administered. The results of the biopsy will also be accessible at a similar time, and these can help to guide chemotherapeutic recommendations.
Radiation therapy may be administered preoperatively or postoperatively. In general, radiation therapy will slow wound healing. In cases where radiation is given either before or after surgery, it is important to ensure that there is minimal tension on the wound closure. This requires careful planning prior to and during the initial surgery. In some cases, if local flaps will require extensive dissection in areas away from the tumor bed and outside the proposed radiation field, it may be better to delay primary closure until it is known if tumor margins
