Veterinary Surgical Oncology. Группа авторов

time (Porcellato et al. 2019). In another study, grade using the canine criteria was prognostic for metastasis but no local recurrence (Romanelli et al. 2008). In a study of cats with soft tissue sarcomas that included FISAS and non‐FISAS, modification of the criteria used to grade soft tissue sarcomas in canines was applied and was prognostic for survival time: median survival time for cats with low‐grade tumors was 900 days, with intermediate grade 514 days, and high grade 283 days (Dobromylskyj et al. 2021). In this modified system, mitotic score and tumor necrosis score were the same as in canine tumors, but inflammation score was used instead of tumor cell differentiation score (Dobromylskyj et al. 2021).

Aggressive first surgical excision with wide (Figure 4.8) to radical (3–5 cm) margins results in the best tumor‐free interval and survival time in cats with soft tissue FSA. Cats with complete excisions have significantly longer median tumor‐free interval (>16 vs. 4 months) and survival time (>16 vs. 9 months) than those with incomplete excisions (Davidson et al. 1997). Marginal excision is the major reason that high recurrence rates (up to 70%) have been reported (Davidson et al. 1997; Hershey et al. 2000). Advanced imaging of the tumor is recommended (McEntee and Samii 2000; Morrison and Star 2001) for appropriate treatment planning. Median time to recurrence was significantly longer when a cat was operated by a specialist surgeon (274 days) compared to a referring veterinarian (66 days) (Hershey et al. 2000). Other prognostic factors for survival time that are significant include local recurrence, presence of distant metastasis, and the number of surgeries (Cohen et al. 2001; Eckstein et al. 2009; Romanelli et al. 2008). Overall reported median survival time after surgical treatment has been 11.5–20.3 months (Davidson et al. 1997; Dillon et al. 2005), and median survival time after complete excisions (>16 months) has been significantly longer compared to incomplete excisions (9 months) (Davidson et al. 1997).

Figure 4.8 (a) Wide excision of a feline injection‐site‐associated sarcoma. The skin incision has been performed around the subcutaneous tumor. (b) En bloc resection of tumor mass and surrounding tissue barrier. (c) Visible dorsal spinous processes (arrows) of cervical vertebrae after tumor removal. (d) Closure in layers with simple interrupted suture patterns. Blue nylon skin sutures are visible.

The most important prognostic factor for local recurrence, and subsequent survival time, is the achievement of clean surgical margins (Banerji and Kanjilal 2006; Cronin et al. 1998; Hershey et al. 2000; Kobayashi et al. 2002). Cats undergoing limb amputation for FISAS did better than local excision anywhere else on the body (Hershey et al. 2000). Size of the tumor has been reported to influence survival time after surgery (Cohen et al. 2001; Dillon et al. 2005; Spugnini et al. 2007b). To achieve wide tumor resection, resection of the dorsal portion of interscapular vertebral spinous processes, partial scapulectomy (Trout et al. 1995), lateral body wall resection (Lidbetter et al. 2002), and hemipelvectomy (Barbur et al. 2015; Straw et al. 1992) may be necessary (Davidson et al. 1997; Davis et al. 2007; Hershey et al. 2000; Romanelli et al. 2008). Some surgeons promote using wider surgical margins than the commonly recommended 2–3 cm lateral margins with one tissue plane in depth, because of the high recurrence rate of FISAS. Fifty‐seven cats with FISASs were treated by wide resection using 4–5 cm lateral margins and one fascial plane deep to the tumor, including partial scapulectomy and removal of dorsal spinal processes if indicated. Histologically complete resections were reported for 95% of the tumors; 5% had tumor cells in the margins. Local tumor recurrence developed in 39%, with distant metastasis in 21%. About 51% of the cats were alive at an overall median follow‐up period of 366 days (median follow‐up period for the alive cats was 600 days) (Romanelli et al. 2008).

Phelps et al. (2011) reported in a case series on 91 cats treated by radical excision with five‐centimeter margins including 2 muscle planes or bone deep to the tumor (Figure 4.9). Any anatomic structures that fell within the determined margins were excised, including thoracic wall, abdominal wall, dorsal spinous processes, ilial wing, and scapula. If the tumor was subcutaneous and could be elevated away from underlying structures with 5‐cm margins, the underlying structures were not excised. Although excision of FISAS resulted in a metastasis rate similar to rates reported previously, the local recurrence rate appeared to be substantially less than rates reported after less aggressive surgeries. Overall median survival time was 901 days. Out of 91, 13 (14%) cats had local tumor recurrence, 18 (20%) cats had evidence of metastasis after surgery. The median survival time of cats with and without recurrence was 499 and 1461 days, respectively. The MST of cats with and without metastasis was 388 and 1528 days, respectively. Tumor recurrence and metastasis were significantly associated with survival time, whereas other examined variables were not. Major complications occurred in 10 cats, including 7 with incisional dehiscence. The best predictor for the development of wound healing complications after wide excision of FISAS is an increased duration of surgery (Cantatore et al. 2014).

Figure 4.9 Radical excision of a feline injection‐site‐associated sarcoma. (a) Five cm margins are measured and marked with sterile marker on the skin. (b) The radical excision required abdominal body wall excision and excision of facias in the pelvic limb and over the epaxial muscles, en bloc with the tumor. (c) It was possible to close the skin defect primarily, without the use of reconstructive techniques, which is often the case in cats after radical excision.

      It is important to consider that the margin size will alter directly after removal of the specimen. Significant decreases in surgical margin length in FISASs specimens occur immediately following excision (prior to formalin fixation). Median tumor volume decreases significantly between in vivo and ex vivo assessments regardless whether measurements are obtained from 2‐D or 3‐D CT images. Subgross evaluation of tumor‐free margins from on‐slide grossly normal surgical margins to pathologist‐reported histologic tumor‐free margin overestimates the actual (histologic) tumor‐free margins (Terry et al. 2016, 2017).

      Radical surgery is easier with the guidance of advanced imaging in the form of CT or MRI compared to manual palpation. Preoperatively the skin is marked as required for sufficient margins. Available amount of skin for closure has to be assessed preoperatively. If insufficient, a skin flap can be used (Montinaro et al. 2015), or skin stretcher can help to recruit extra skin in two to three days. Changes in the muscular form according to the forelimb positioning must be appreciated. It is important to have an in‐depth anatomical knowledge of the interscapular region of the feline patient to approach the study of any pathology located there and, in particular, to set up an appropriate therapy for the FISASs (Longo et al. 2015).

Adjuvant radiation therapy can improve outcomes. Median DFIs after complete resection combined with radiation therapy were 405–1110 days. Survival times after complete resection combined with radiation therapy were 476–1290 days. DFIs after resection with contaminated margins combined with radiation therapy were 112–600 days. Median survival times for contaminated margins combined with radiotherapy were 502–900 days (Cohen et al. 2001; Cronin et al. 1998; Eckstein et al. 2009). According to Eckstein et al. (2009), radiation therapy of residual microscopic tumor improves median DFI and survival time (20 and 30 months, respectively) compared to residual macroscopic tumor (4 and 7 months, respectively). However, even with neoadjuvant radiation therapy and complete margins after surgical excision, local recurrence has been reported to be 42% (Kobayashi et al. 2002).

      In a study of 76 cats with vaccine‐associated