We report our experience that even extensive anal fistula cancer can be radically resected by reconstruction using an appropriate myocutaneous flap.

Repeated inflammation might predispose the risk factor for development of anal fistula cancer [3]. Increased circulating concentrations of cytokines due to chronic inflammation might influence tumor formation [7]. Patients are usually diagnosed as locally advanced cancer as the rate of definitive diagnosis from a single biopsy tissue is low at 40% [4]. Because the tumor in anal fistula dose not usually pierce the rectal mucosa unless cancer is far advanced. In addition, as the symptom mimic benign inflammatory condition such as perianal oozing or mucinous discharge, the early diagnosis of anal fistula cancer might be missed. Therefore, curative resection for anal fistula cancer requires extensive perineal skin incision and wide perineal tissue excision. APR with the extensive resection and myocutaneous flap reconstruction is often performed for curative resection of anal fistula cancer. Previous case studies have reported about extended APR and myocutaneous flap reconstruction for anal fistula cancer (Table 1) [5, 6, 8,9,10]. Myocutaneous flap reconstruction might allow wide-ranging extended resection of anal fistula cancer, and then lead to radical resection.

We used posterior thigh myocutaneous flap in Case 1 and gluteus maximus myocutaneous flap in Case 2 to repair the perineal defect caused by APR. Optimal myocutaneous flap conditions include good blood flow, close proximity to the postoperative tissue defect, adequate coverage of the defect area, and minimal functional loss due to myocutaneous flap harvesting. Flaps that meet these conditions after APR include the vertical rectus abdominis myocutaneous flap, posterior thigh myocutaneous flap, gluteus maximus myocutaneous flap and gracilis myocutaneous flap, etc. The vertical rectus abdominis myocutaneous flap is widely reported and most used in flap reconstruction after APR [11]. The vertical rectus abdominis myocutaneous flap has the advantage of a long robust pedicle, abundant volume and surface area, ease of harvest while spine position and low incidence of necrosis [12]. However, there are several reasons to limit the use of vertical rectus abdominis myocutaneous flap. These include situations where the rectus abdominis muscle or inferior epigastric vessels have been previously divided, unfavorable abdominal incisions and scarring and the presence of stomas exiting through the rectus abdominis muscle [13]. The posterior thigh flap is robust, easy to raise, and can provide abundant skin and muscle. It does not involve separating the muscles and does not necessarily result in lower limb motor dysfunction, and donor site morbidity is minimal provided direct closure is possible. However, the thigh scars are long and require prone positioning. The posterior thigh flap can be successfully used in the situation to provide both soft-tissue coverage and functional pelvic reconstructions [12, 13]. The gluteus maximus myocutaneous flap is technically easy to raise and provide ample skin and fat. This flap is used mainly for posterior perineal defects but can be extended to reach anterior defects. However, gluteal flaps require prone positioning and usually need to be bilateral [12, 14]. The gracilis myocutaneous flap has the advantage that thin and long muscle can be easily harvested in a spine position, and there is almost no functional sacrifice associated with muscle harvesting. Disadvantages include a lower amount of tissue and a higher risk of flap necrosis compared to the other flaps mentioned above [12]. In Case1, the patient had history of abdominal surgery and the patient underwent laparoscopic APR with extensive buttock resection and sacral resection. The vertical rectus abdominis myocutaneous flap is useful when the perineal defect involves the anterior pelvic compartment but it is not sufficient to fill the posterior pelvic compartments particularly after partial sacretomy [14]. The posterior thigh flap was considered appropriate to fill the large defect with a sufficient amount of skin and muscle. In Case 2, the patient had history of abdominal surgery and had a colostomy. Therefore, flaps arising from the lower extremities were preferable, and considering the size of the defect wound from this surgery, we used expanded gluteus maximus flaps. Regarding postoperative activities of daily living, although both cases felt skin tightness at the surgical site, they were able to walk to the hospital. Our experience with 2 cases shows that there are various options for myocutaneous flap reconstruction used in laparoscopic perineal resection. Therefore, it is necessary to use different myocutaneous flaps depending on their characteristics.

The use of adjuvant therapy is thought to affect patient prognosis; however, there are currently no clear standards for adjuvant therapy. Some case reports in Table 1 have indicated that the prognosis may be improved by adjuvant therapy. We suggest that it is feasible to consider the use of adjuvant therapy, in cases where postoperative adjuvant chemotherapy is deemed suitable. In our department, as with postoperative adjuvant chemotherapy for colorectal cancer, we offer postoperative adjuvant chemotherapy for stage III and high-risk stage II cases. As in the present cases, adjuvant chemotherapy is also administered in cases of suspected positive resection margins.

Although not performed in the present cases, preoperative chemoradiotherapy (CRT) has been reported to be beneficial in ensuring resection margins. Considering the local control effect of preoperative CRT for rectal cancer, preoperative CRT for anal fistula cancer may improve local control and prognosis [15, 16]. In our two cases, though pathological resection margin was suspected positive, a combination of preoperative treatment and extensive surgery could have yielded negative margins.