the needle after being acquired. (b) The end of the needle is tapered, helping to keep the sample in the needle when the needle is removed from the bone. (c) To remove the sample from the needle, the stylet is introduced through the tip of the needle and the sample is pushed to exit the base at the handle. In some instances, there is too much resistance to push the sample out of the handle end, in which case the first stylet is used to push the sample out through the tip. It is not ideal because in theory the sample can suffer some damage going through the narrowed end, but sometimes it is necessary.
Endoscopic Biopsy
Esophagoscopy, gastroscopy, duodenoscopy, and colonoscopy are routinely performed in veterinary medicine as minimally invasive techniques to attain biopsies of the gastrointestinal tract. Biopsies attained during these procedures are generally smaller than what can be achieved with an open procedure; however, the biopsies are often diagnostic, and the morbidity associated with these procedures is reduced over open procedures (Magne 1995; Moore 2003).
Laparoscopy and thoracoscopy are still relatively underutilized modalities, but successful procurement of kidney, bladder, liver, spleen, adrenal gland, pancreas, stomach, intestine, and lung biopsies have been described by the use of these procedures (Rawlings et al. 2002; Lansdowne et al. 2005; Vaden 2005; Barnes et al. 2006). Case selection is essential when considering these minimally invasive alternatives, as cases that have excessively large tumors or other potential contraindications should undergo an open procedure.
Laparoscopy and thoracoscopy may have a role in the staging of veterinary patients as the use of these techniques increases. In cases where lymph node evaluation and biopsy would assist in predicting outcome or determining treatment, these procedures could be performed by minimally invasive techniques (Fagotti et al. 2007; Steffey et al. 2015; Lim et al. 2017).
Surgical Considerations for Curative‐Intent Surgery
Certain surgical technical principles will improve the chance of success and minimize the risk of local or distant seeding of tumor cells. The tumor should be draped off from the rest of the surgical field. Surgeons should attempt to not contact ulcerated or open areas of tumor with gloves or instruments. Sharp dissection is preferred over blunt dissection, when possible, as this will decrease the likelihood of leaving neoplastic cells within the patient and decrease the risk of straying from the preestablished margin. Tension on skin closures should be avoided whenever possible, especially in cases that have undergone radiotherapy. Proper knowledge of tension‐relieving techniques such as tension‐relieving sutures and flaps can assist in closure (Soderstrom and Gilson 1995; Aiken 2003); however, tension‐relieving skin incisions are contraindicated after removal of a neoplasm. If an indwelling drain is deemed necessary in a tumor resection site, the drain should be located in an area that can be resected during a subsequent surgery or in an area that will not compromise radiation therapy and can easily be included in the radiation field. Lastly, control of hemostasis and prevention of seroma or abscess development due to dead space is encouraged. Seromas or hematomas following an incomplete resection allow tumor cells to gain access to areas beyond the surgical field as these fluids may be widely dispersed throughout the subcutaneous space during movement.
To decrease the risk of recurrence after tumor resection, there are several techniques that the surgeon should practice. For tumors that have been previously biopsied or for which a drain has been placed, the biopsy tract and/or drain hole need to be removed en bloc with the tumor. Similarly, adhesions should be removed en bloc with the tumor, when possible. Leaving any of these can result in an increased risk of tumor recurrence. Additionally, when establishing a margin during surgical dissection, this margin must be maintained around the periphery of the tumor down to the deep margin. Straying from this may result in an incomplete resection. Similarly, the pseudocapsule present around a tumor should not be penetrated, as this pseudocapsule is constructed of a compressed layer of neoplastic cells (Soderstrom and Gilson 1995). Seeding of these cells will likely result in recurrence, and healing may be inhibited. Lastly, it is important that a new set of instruments, gloves, and possibly drapes be utilized for closure of a wound created by tumor removal or reconstruction of a wound. This principle applies to the removal of subsequent tumors on the same patient, as these items should not be transferred from one surgical site to another.
Defining and Evaluating Surgical Margins
The evaluation of surgical margins of an excised specimen is an essential component to appropriate care in a cancer patient. A surgical margin denotes a tissue plane established at the time of surgical excision, the tissue beyond which remains in the patient. Excised masses should be submitted in their entirety for evaluation of the completeness of excision. The surgeon should indicate the margins with ink or some other method prior to placing the specimen in formalin to aid the pathologist in identifying the actual surgical margin. Because the larger tumor specimen is trimmed by a technician to fit on a microscope slide, the pathologist may not be oriented as to what represents a surgical margin versus a sectioning “margin.” Tissue ink on the surgical margin allows there to be orientation throughout sectioning. The ink is present throughout the processing of the tumor specimen and is visible on the slide. If tumor cells are seen at the inked margin under the microscope, the surgical margin is by definition “dirty” or incomplete.
There is considerable confusion and controversy surrounding the issue of appropriate surgical margins and clinical decision‐making when histologically incomplete margins are obtained. Prior dogma has suggested that an overly generous margin is likely to be curative. In order to ensure a good oncological outcome, surgical oncologists have been trained to be as aggressive as possible. While it is well‐accepted that aggressive surgical margins tend to lead to better local control, this is not true in every case. Even extensive, complete surgical margins do not always lead to a cure. Local recurrence and/or metastasis may occur despite a histologically complete margin. Mounting evidence in the human sarcoma literature seems to suggest that a planned and executed “widest” surgical margin has not resulted in sufficient improvements in disease‐free intervals to justify the morbidity incurred with such resections. This opinion among human surgeons is confounded by the routine use of adjuvant radiation therapy in traditionally difficult‐to‐resect tumors such as extremity sarcomas. In veterinary medicine, adjuvant radiation therapy may not be available or affordable. As we know from experience and from the veterinary literature, not every patient with a histologically positive margin will experience recurrence. To confound things further, different malignancies and grades of malignancy (mast cell tumor vs. soft tissue sarcoma, low grade vs. high grade) may require specific and separate guidelines for margin planning.
Veterinary surgical oncology has traditionally followed the adage that for most malignant solid tumors, a 2–3 cm surgical margin and an additional tissue plane deep is the desired intraoperative goal to achieve wide excision, and is most likely to result in a histologically clean excision. Nonetheless, many surgical oncologists bend these “rules” based on tumor‐specific evidence in the literature and personal experience. Examples of this include using proportional margins in mast cell tumor resection (Pratschke et al. 2013) or less generous margins for specific anatomic areas, where 2–3 cm could result in undesirable functional morbidity (e.g. head and neck, spinal column). Many, based on experience, feel comfortable with smaller margins in specific tumor types (anal sac tumors, thyroid tumors, low‐grade sarcomas) and in some cases, this is supported in the veterinary literature by findings of no difference in local recurrence between one “width of margin” and a lesser one. However, the minimum safe distance necessary to reduce the chance of local recurrence is currently unknown. Regardless of what is actually performed in the operating room, most of the published literature agrees that a histologic margin free of tumor cells is considered the best predictor of improved local recurrence.
Varying Definitions of “Margin”
