Soft tissue sarcomas of the popliteal fossa are extremely rare tumors of mesenchymal origin accounting for 3–5% of all extremity sarcomas. Turcotte et al. reported this rate as 2.7% in their series [1]. In the present sarcoma series, the incidence rate of popliteal fossa sarcomas was 1.3%. Recent studies showed that the use of radio-chemotherapy could produce limb-sparing rates of 65–95% [7, 8], which was 87.5% in the present cohort. Surgical margins are one of the most important factors affecting local recurrence [9]. In this study, the adventitia or the nerve sheath was routinely removed when the vessels or nerve was in close proximity. In a recent study authors reported that although the close proximity, vital tissues were surrounded by the tumor only in 11.5%. They concluded that carcinomas infiltrate, sarcomas displace the vessel and nerve [10]. Negative margins plus radiotherapy provide lower rates of local recurrence [11]. Radiation therapy has been reported as an adjuvant that improves the local recurrence rates [12]. However, radiotherapy is unable to control the positive margins. Local recurrences after popliteal soft tissue tumors are usually encountered within 2 years after the initial procedure [13]. Local recurrence after limb salvage was recorded in the present study in six patients (25%). Only in one patient, the surgical margins were positive. In four patients, lymph node metastasis was detected. In this regard, lymph node or distant metastasis might be predictive factors for a local recurrence. Turcotte et al. reported the recurrence rate of positive margin as 9% (1/11) in their series of 18 patients. In the present series, only one patient had positive margins, who had a local recurrence. The relationship between local recurrence and survival remains unclear. Two patients with local recurrence underwent amputation, and they had local recurrence. Also, lung metastases developed in one of them. Two deaths occurred due to synovial sarcoma and malignant peripheral nerve shield tumor because of metastasis at diagnosis and early-term follow-up, respectively. The mean event-free survival was 13.8 months. Pritsch et al reported a series of 27 cases. They reported that 7% of patients had metastatic disease at diagnosis. The amputation rate was 14%. They also reported no difference between the amputees and the limb-salvage group according to survival [7]. The rate of local recurrence was 10% and the wound complication rate was 30%, in their series. In this study, the rate of metastatic disease at diagnosis was 25%. The amputation rate was 13%, the local recurrence rate was 25%, the total complication rate was 29%, and the wound complication rate was 25%. Five-sixth of local recurrence cases and surgical margins were negative. This result was attributed to the fact that the surgical margins < 1 cm were accepted as intact. Neoadjuvant radiotherapy had a negative impact on wound tissue healing [14]. Also, radiation-induced fibrosis, lymphedema, and joint stiffness might alter the functional scores [15, 16]. In this study, no relationship was found between neoadjuvant radiotherapy and wound complications/lower functional scores. Wound complications might alter the functional scores. However, in this study, no complications were encountered in a patient in whom the medial hamstring and medial head of the biceps muscle with neoadjuvant radiotherapy were resected. In another patient, the gastrocnemious lateral head was resected, and no complications were encountered. In two other patients, the posteromedial corner reconstruction with allograft and rotational gastrocnemious flap was made with postoperative radiotherapy. No complications were encountered, and the mean TESS score was 85 in these two patients. Turcotte et al. reported the TESS and MSTS 1987 mean scores as 82.4% and 33/35, respectively. Bickels et al. reported 15 patients who underwent sciatic nerve resection. They reported good functional results [1].. The mean TESS and MTST 1993 scores were 77.4% and 81.2%, respectively, in this study. The sacrificed nerve branches of the sciatic nerve did not reduce the functional results. All below-average functional scores and local recurrences might belong to neurovascular stripping. Also, amputation, multiple metastases, and fracture might belong to lower scores. All preferences on the present series are given in Table 1. Data regarding detailed analysis of neurovascular involvement are limited. In two patients, the margins were positive. Four neural resections and three vascular by-passes were performed. Only in two patients who underwent neurovascular stripping (margins < 1 cm), local recurrence was detected. Hohenberger et al. reported 20 patients with soft tissue sarcoma invading neurovascular structures, but only four patients had popliteal fossa tumors [18]. No other study has evaluated neurovascular involvement so far. In the present study, five neural and eight vascular invasions were detected. Of the 20 patients with neurovascular stripping, only 5 (25%) had a local recurrence. Of the six patients with local recurrence, four patients had no pre-/postoperative radiotherapy.
The present study had several limitations. It was a retrospective study and was relatively small and heterogeneous. Second, the minimum follow-up was only 2 years. However, to our knowledge, this report is one of the largest series about popliteal soft tissue sarcomas in English literature. The rates of local recurrence and systemic disease increased only slightly during a longer follow-up because local recurrence and metastasis usually occur in first two years, and the median follow-up in this study was more than 70 months [10].
In conclusion, microscopically positive margins may not be an absolute indication for amputation. Also, negative margins do not provide a guarantee that local recurrence will not occur. Lymph node or distant metastases may be predictive factors for local recurrence rather than positive margins. Metastases at diagnosis or early term after surgery might increase the local recurrence despite negative margins. Therefore, in these patients, preoperative radiotherapy was suggested despite wound complication risk. Irradiation before re-resection in positive margins is not recommended; instead, the re-resection should be done first, followed by radiotherapy.