Figure 4.7 Excision of STS at distal medial aspect of the metatarsus using a phalangeal fillet flap of digit II in a Heidewachtel. (a) Tumor and 1 cm excision margins drawn on the skin. (b) En‐bloc excision including metacarpal II and digit II and metacarpal III, metacarpophalangeal joint and proximal part of phalanx I of digit II, preserving the main blood supply of digit III. (c) Removal of the bones and nail of digit III (“fillet”), preserving soft tissues and blood supply. (d) Raising and rotating the phalangeal fillet flap into the defect. Note that the digital pad is preserved. This technique is also useful for footpad reconstruction. (e, f) Result after one week.

Although elliptical excisions are commonly used for skin tumor removal, several human studies claim to have better results with round excisions. Furthermore, the shape of the tissue to be excised is dictated by the tumor margins, which commonly results in more or less round wounds. In practice, only the lesion and the required margin of surrounding tissue are excised without attempting to design an elliptical skin incision. The resulting wound is closed by opposing the wound edges along the lines of least skin tension, starting in the center of the wound. Such round excisions result in 14–21% shorter sutured wound length and the wound direction differed from the predicted ellipse in 45% of cases (Hudson‐Peacock and Lawrence 1995). When using this technique, dog‐ears will obviously appear. In general, however, round excision with subsequent dog‐ear removal results in better‐oriented wounds than those achieved by elliptical excision, minimize tissue excision, decrease wound widening, and may still decrease the final sutured wound length (Lee et al. 2011). Dog‐ear reconstructions are relatively simple and can be performed directly after closure or at a later time (Borges 1982) by removal of the excess skin fold and thus extending the wound length. Techniques to reduce dog‐ear folds without removal of skin include suture techniques to anchor the dog‐ear to deeper tissues such as the dog‐ear tacking suture technique (Kantor 2015) and the three‐bite suture technique (Jaber et al. 2015). In the latter technique, a three‐bite suture is placed that sequentially pierces the deep fascial plane and each margin of the dog‐ear, thus flattening the dog‐ear by anchoring the over‐projecting skin to the deep plane. This is a fast, easy, and versatile method of immediate dog‐ear correction without extending the scar while maintaining a full and complete local skin blood supply (Jaber et al. 2015).

      Another rarely discussed reconstructive technique is the cuticular purse string technique. In a retrospective study by Cohen et al. (2007), the authors reviewed 98 human patients after cuticular purse‐string suture placement. These sutures will achieve partial surgical wound closure and the postoperative wound area decreased by 6–90%, with a mean of 60% following purse‐string partial closure. The circumferential placement of the cuticular purse‐string suture makes it possible to recruit skin from the entire diameter without needing to undermine the wound edges. Generally, the purse string suture is removed three or four weeks after closure to allow the partially closed wound to completely heal by second intention. According to the authors of this study, this closure technique provides uniform tension to the wound, enhances hemostasis at the tissue edge, and significantly decreases the size of the defect. The technique has been described in people after surgical removal of skin tumors (Cohen et al. 2007) and is reported to be particularly suitable in older human patients because of their skin laxity (Raposia et al. 2014).

      Pavletic (2000) described the use of skin stretchers 72–96 hours before excision of large tumors. Skin stretching is an easy way to mobilize skin and is reported to be successful in most cases. Two other techniques for stretching the skin after creating the surgical wound have been studied: staples as anchor points along the edge of each surgical wound margin and a hypodermic needle “skewered” through the skin parallel to each surgical wound margin (needle transpiercing the skin along the length of the margin, going in and out of the skin). Sutures are then placed between the staples or the needles on either side of the wound and tightened over a bandage material covering the open wound (Tsioli 2015).

      Cryosurgery

      Cryosurgery is a type of cytoreductive therapy that has been described for superficial skin tumors. Cryosurgery may be used in cases when surgery is not possible because of concurrent debilitating factors that prevent safe anesthesia. Cryosurgical ablation uses tissue freezing to destroy selected lesions. There are several methods of cryosurgery: open‐spray, closed‐spray, and cryoprobe method. Liquid nitrogen is sprayed on the tumor from a specified distance for 15–60 seconds. For malignant lesions, two to three freeze‐thaw cycles are recommended, while for benign lesions, two cycles are recommended. Before application, large vessels feeding the tumor may be ligated to prevent hemorrhage and to improve the freezing effect. Wounds heal by second intention. Patients should be closely monitored following cryosurgery to control the healing of the treated site and to treat possible complications. Reported complications include hemorrhage, pain, edema, depigmentation, tissue retraction, tendon rupture, alopecia, odor, and lameness (De Queiroz et al. 2008).

      Adjuvant Therapies

      According to several studies, surgical resection, often described as “aggressive,” “radical,” or “wide,” is the first or primary treatment of choice with the best overall outcome in STS treatment. The surgical goal should always be removal of the complete tumor. If complete tumor removal is not achievable, for instance where there are important adjacent anatomical structures, cytoreductive surgery can be used as palliative care or in combination with adjunctive therapies. Multimodal therapy including adjuvant radiotherapy and/or chemotherapy may allow reduction in surgical dose without compromising local recurrence rates (Bostock and Dye 1980; Bray 2016; Davidson et al. 1997; Dernell et al. 1998; Ehrhart 2005; Liptak and Forrest 2013). Palliative care can be used to reach an acceptable survival time and, above all, a reasonable quality of living.

       Radiotherapy

External beam radiation sources include X‐rays, gamma rays, or electrons delivered by orthovoltage or megavoltage (linear accelerators and cobalt 60) equipment. When X‐rays and gamma rays interact with tissue, they transfer their energy, leading to chemical and biologic damage, damaged DNA, and finally cell death. Radiotherapy can be used in a curative or palliative manner before (neoadjuvant) or after (adjuvant) surgical tumor removal. A definitive course of radiotherapy often involves daily treatments for several days under general anesthesia. Radiation protocols, however, vary based on the tumor type, stage, and site, and from one facility to another. Palliative (coarsely fractioned) radiation therapy has been used for pain relief and improvement of dysfunction in people and in animals suffering from neoplasia.

      Treatment