Outcome of Soft Tissue Popliteal Sarcomas: 15 Years of Experience

Abstract

Background

Soft-tissue sarcoma involving the popliteal fossa remains challenging because it is difficult to achieve wide margins with limb salvage in this location. Adjuvant therapy is frequently necessary, and limb function can be adversely affected. We reviewed our experience with these tumors. A variety of lesions can be identified within the posterior knee, ranging from simple Baker’s cysts to malignant lesions. We present a review of frequently encountered and less common entities using an anatomic sieve, with the aim of providing a diagnostic approach to popliteal fossa masses Soft-tissue sarcomas (STSs) arising from the popliteal fossa present a challenge with regard to local control of primary tumors.

Method

In the study, patients who were operated for a mass in the popliteal region between 2007 and 2018 in our clinic were retrospectively analyzed. Patients were categorized by parameters such as age, gender, extremity direction, type of surgery, AJCC scores, surgical margin, tumor size, presence of distant metastases, mass pathology, follow-up time and MSTS score

Results

Our study included 13 patients (eight women and five men). The mean age was 48 (range 12–84) years. The mass was located in the left knee in nine patients and the right knee in four patients. Frequent histologic diagnoses were for maliğn soft-tissue tumor liposarcoma (n= 5), synovial sarcoma (n= 3) and pleomorphic sarcoma (n= 2), rabdomyorsarcoma, clear cell sarcoma, peripheral nerve sheath tumor (n=1). Tumor size varied from 3 to 14 cm (median 7 cm). American Joint Committee on Cancer staging was as follows: three patients had stage IIA disease, five patients had stage IIB disease, two patients had stage III and stage IB and 1 patient had stage IV disease. The mean duration of follow-up was 39 (range 12–96) months. All patients underwent wide resection. Recurrence developed in four of these patients during the 5-year follow-up period. Recurrence resection was performed in three of the patients who developed recurrence, while recurrence resection + femur distal tumor resection arthroplasty was performed in one patient. In addition, 3 of these 13 patients received neoadjuvant chemotherapy, while 5 received adjuvant chemotherapy treatment. Neoadjuvant RT was applied to 4 patients with a mass greater than 9 cm. Margins were negative in seven of 13 patients and microscopically positive in five patients. Complications included wound infections in four patients and thrombophlebitis in two patients and one patients peroneal nerve nöropraxy. Of the patients undergoing limb-salvaging procedures, two experienced local recurrences after limb salvage and four experienced lung metastases. Local recurrence was always associated with positive margins. The mean MusculoskeletalTumor Society 1987 score was 50 ( range 35–68). At latest follow-up, six patients had died of disease, one was alive with disease, and five patients remained free of disease. 

Conclusion

The popliteal region is a rare area in terms of mass localizations. Inpatients presenting with knee pain, regardless of external findings such as swelling ornot, tumors located in the popliteal region should be considered in patients withoutpathology on direct radiography.

Introduction

The popliteal fossa is bounded proximally by the hamstring tendons, distally by the gastrocnemius muscles, anteriorly by the posterior knee joint capsule and posteriorly by the deep fascia, and contains the popliteal artery and vene, posterior tibial and common peroneal nerves. Soft-tissue sarcomas (STSs) are a rare type of neoplasm that accounts for 2% of all malignancies [1]. Their formation in the popliteal fossa constitutes 3–5% of all extremity and trunk [2]. STSs are rare type of mesenchyme originated tumors and constitute approximately 1% of all adult cancers [3]. While the extremities represent one of the most common primary locations for STS, the popliteal fossa is an anatomic site that is relatively uncommon and presents unique management challenges [4]. Resection is challenging due to extra-compartmental location and proximity to neurovascular structures. Damage to neurovascular structures in the surgical approach causes a functional disability. Therefore, it is essential to know the anatomy [5].

The treatment method is shifted from amputation to limb-preserving surgery within years. At present, a multidisciplinary approach is regularly involved. However, adequate surgical resection is still the mainstay of primary regional treatment for STS, with the size and grade of the tumor reported to be essential factors for survival by previous studies [6, 7]. These replace the fact that microscopic disease can often be controlled with radiotherapy and previously unresectable tumors may become resectable after neoadjuvant chemotherapy. The resection of the sciatic nerve or its major branches is not a contraindication to the limb-salvage procedure [8–11].

However, there are limited data regarding the clinical presentation, characteristics, and outcome of patients with this challenging presentation of STS. In addition, aggressive local control, such as adding radiation therapy either before or after resection, may have an increased risk of functional morbidity [12].

The primary goal of this study was to examine our institution’s experience with patients diagnosed and treated for STS of the popliteal fossa and evaluate the risk factors.

Methods

This research was conducted in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments. The study was approved by the local ethical committee (No: E-77082166–604.01.02–730786). Our prospective tumor patient database served to identify all eligible participants. We identified 24 patients diagnosed with soft-tissue sarcomas of the popliteal fossa treated between 2007 and 2022. Eligibility criteria included patients with deep popliteal sarcomas with at least nine months of follow-up for all survivors. Tumors included those involving the popliteal area and those extending beyond its borders.

Surgeries were planned by same surgical team, led by orthopedic oncologist expert. Each patient was prepared, in the prone position and both extremities were surgically prepared for limb-salvage surgery. The aim is to use the saphenous vein of the contralateral side as a graft if resection of the popliteal artery is required. After making an “S”-shaped incision from the femur, starting from the lateral proximal to the tibia and ending at the distal medial, the skin was lifted as a flap. Both heads of gastrocnemius and hamstring muscles were dissected and retracted to optimize the field of view. Wide resection was planned to all patients and after wide resection, the remaining anatomic landmarks were repaired and separated muscles were reconstructed as a unified muscular cover and closed.

We performed a retrospective chart review to obtain and update the necessary information for each participant. We examined the radiologic imaging to ensure the involvement of the popliteal area, and the diagnosis was performed via biopsy. Collected data included demographic and tumor characteristics such as diagnosis, grade, size, surgical margin (Categorized as negative, positive and near positive) and recurrence; treatment protocols, such as surgery, chemotherapy, and radiotherapy; complications; and oncologic and functional outcomes. We staged tumors by the American Joint Committee on Cancer (AJCC). 14 of the 24 cases were given radiotherapy and/or chemotherapy. The application of radiotherapy or chemotherapy was based on the tumor grade higher than grade 1, tumor type, surgical margin and tumor stage, in accordance with the departments of oncology and radiation oncology, based on our national guidelines [13, 14].

In statistical analysis, categorical and continuous variables were given as numbers, percentages, mean ± standard deviation, median (min–max) values, and descriptive analyses. Chi-square tests were used to compare the categorical variables between groups. The conformity of continuous variables to normal distribution was evaluated by visual (Histogram and probability graphs) and analytical methods (Kolmogorov–Smirnov/Shapiro–Wilk tests), respectively.

Analysis of normality revealed that not all data sets are typically distributed. The Mann–Whitney U and Kruskall–Wallis tests were used to compare the data sets that were not normally distributed for the variables. Spearman correlation was used to test the relationship between tumor size and patients’ age. P < 0.05 was considered statistically significant (Fig. 1).

Fig. 1.

Performing the limb-sparing surgery in popliteal STS

Results

There were no statistical differences in the gender distribution of the patients (Female = 13, male = 11) (p = 0.683). The mean age of the patients at admission was 47.21 ± 20.53 (12–84). The tumor size is 8.79 ± 5.34 (range: 2–22) cm. The mean follow-up period was 32.38 ± 24.22 (range: 9–96) months. The most common malignancy diagnosed in the patients were liposarcoma (20.8%, n = 5), synovial sarcoma (20.8%, n = 5), and pleomorphic sarcoma (16.7%, n = 4), respectively. Data on patient diagnoses are given in Table 1. Wide resection was performed in 87.5% (n = 21) of the patients. According to the pathology results, the surgical margin was negative at 62.5% (n = 15). Recurrence was observed in 29.2% (n = 7) of the cases. Mean time to recurrence was 22.14 ± 11.02 (range: 2–36) months. Amputation was performed in one patient with recurrence, wide resection was performed in five patients, and one patient was followed up palliatively. Demographic data of 24 patients diagnosed with sarcoma in the popliteal region are given in Table 2. Age and tumor size had no significant relationship (r = − 0.088, p = 0.683). When gender and tumor size were compared statistically, no significant relationship was found (p = 0.861). In addition, no significant relationship was found between tumor size with recurrence (p = 0,076) and tumor size with metastatis (p = 0,155).

Table 1.

Baseline demographics (n = 24)

	n	%	Mean ± SD	Median	Min–max
Age			47.21 ± 20.53	53.0	12–84
Sex
Male	11	45.8
Female	13	54.2
Side
Right	6	33.3
Left	16	66.7
Treatment
Total eksizyon	3	12.5
Geniş rezeksiyon	21	87.5
Follow-up period (months)			32.38 ± 24.22	24.50	9–96
Size (cm)			8.79 ± 5.34	7.50	2–22
Recurrence
Yes	7	29.2
No	17	70.8
Surgical margin
Positive	4	16.7
< 1 mm	5	20.8
Negative	15	62.5
Adjuvant therapy
Yes	16	66.7
No	8	33.3
Metastasis
Yes	6	26.08
No	17	73.92

Table 2.

Frequency of diagnosis

	(n = 24)	%
Clear-cell sarcoma	1	4.2
Ewing sarcoma	1	4.2
FibrosarcomA	1	4.2
Leiomyosarcoma	1	4.2
Liposarcoma	5	20.8
Low grade chondrosarcoma	1	4.2
Malignant melanom metastasis	1	4.2
Parosteal osteosarcoma	1	4.2
Periferic nerve sheath tumor	2	8.3
Pleomorphic sarcoma	4	16.7
Rabdomyosarcoma	1	4.2
Synovial sarcoma	5	20.8

The AJCC score at admission was stage IV in 33.3% of the patients at latest follow-up (Table 3). The presence of recurrence could not be shown to have a statistically significant effect on survival (p = 0.235).

Table 3.

Frequency of AJCC Stages

	n (N = 24)	%
Stage IB	4	16.7
Stage IIA	4	16.7
Stage IIB	4	16.7
Stage IIC	1	4.2
Stage IIIA	2	8.3
Stage IIIB	1	4.2
Stage IV	8	33.3

Of the 16 patients who received adjuvant/neoadjuvant therapy, 31.25% (n = 5) received radiotherapy alone, 18.75% (n = 3) chemotherapy alone, and 50% (n = 8) both radiotherapy and chemotherapy. When RT and/or CT was added, the effect of reducing recurrence could not be statistically demonstrated. (p = 0,663).

Metastases were detected in 6 patients (26.08%) during follow-up, which were inguinal and pulmonary metastasis in one patient, peritoneal metastasis in one patient, lung metastasis in one patient, popliteal lymph node metastasis in one patient, and thoracic vertebral metastasis in one patient. It has been observed that adding RT and/or CT in the treatment reduces the metastasis rate statistically significantly (p = 0,041).

No complications were observed during the follow-ups in 66.7% (n = 16) of 16 patients. Peroneal nerve neuropraxia developed in one patient (4.2%), thrombophlebitis in 2 patients (8.3%), and wound infection in 5 patients (20.8%).

At the time of this study, the final status of the patients was followed as 2 of them were (8.3%) alive with disease, 7 of them were (29.2%) died of disease, and 15 of them had (62.5%) relapse-free survival (Fig. 2).

Fig. 2.

MRI section of a popliteal malignant peripheral nerve sheat tumor

Discussion

Popliteal soft-tissue tumors are sporadic and account for 1–5% of all extremity STSs in total [15]. In our case series, popliteal sarcomas constituted only 1.1% of the soft-tissue sarcomas in our prospective database. Although the lower extremity is the region where soft-tissue sarcomas are most frequently observed, the reason why popliteal sarcomas are so rare can be explained by their high vascularity, being entirely surrounded by the joint capsule, being resistant to tumor invasion and being extra-compartmental [16].

Although rare, resection of popliteal sarcomas with wide surgical margins is quite challenging due to proximity to neurovascular structures, reducing the chance of success and increasing the complication rate. For this reason, while the preferred surgical method in the past was amputation, it resulted in irreversible loss of function and a decrease in the patient’s quality of life. It has been shown that amputation has no positive effect on distant metastasis and survival [17, 18]. In addition, studies are showing that neurovascular invasion does not affect amputation and clinical outcomes [3].

In current treatment approaches, limb-sparing surgery is the primary choice of treatment. It has been reported that the addition of radiotherapy results in better results than surgical treatment alone and is a viable alternative to amputation surgery. Even though the effect of radiotherapy on the recurrence rate could not be demonstrated in our case series, we attribute the fact that it significantly reduced metastasis development to a positive effect on survival. It is also reported that radiotherapy reduces amputation rates when applied on time [19]. The rate of amputation in our clinic was % 4,1. Although the secondary amputation rate varies in other studies, this rate is around 20–35% in early studies can be interpreted as the widespread use of radiotherapy playing an essential role in reducing the amputation rate. In our case series, the sole amputation case was a case of pleomorphic sarcoma who had refused radiotherapy the first time, and did not follow-up appropriately. When applied again, the limb had to be amputated because of progression. Neoadjuvant therapy is beneficial in cases where surgical margin negativity is difficult to achieve. However, postoperative radiotherapy can also be given independently of the surgical margin, depending on the grade of the tumor. There is no standard approach in this aspect, and it can be given in low-grade sarcomas with positive surgical margins and in higher-grade sarcomas regardless of surgical margin [20].

In our case series, the surgical margin was positive in only one of seven patients who developed recurrence, suggesting that recurrence is independent of the surgical margin. The recurrence rate varies in the literature, varying between % 7–30 [21]. Although the surgical margin is one of the most important factors affecting local recurrence, different factors may come to the fore according to the tumor type. In a retrospective analysis of 171 synovial sarcoma cases, factors affecting local recurrence were reported to increase local recurrence by tumor size greater than 5 cm, not receiving postoperative radiotherapy, marginal resection, and multiple recurrences in addition to positive surgical margin [22]. In our series, all of the synovial sarcoma cases that showed recurrence were over 5 cm and developed despite receiving chemoradiation,

It has been stated that recurrences after 2 years generally develop independently of surgical margin positivity and adversely affect the prognosis. This phenomenon was thought to be due to the histologically aggressive nature of the tumor [23]. For this reason, long-term close follow-up is of great importance and benefit in detecting a potential recurrence and providing appropriate treatment to increase survival.

Conclusion

The main goal in popliteal sarcomas is to achieve negative surgical margins. However, the proximity of neurovascular structures and vulnerability to invasion make this very difficult. Positive surgical margins or involvement of neurovascular structures, although challenging, is not an absolute indication for amputation; limb-sparing surgery can be performed with reconstructive options such as bypass and satisfactory results can be achieved. In addition, since the popliteal region may be problematic for wide resection, we think that neoadjuvant and adjuvant radiotherapy are practical options, although we have not been able to show its effect on recurrence. Regardless of the surgical margin, recurrence can be seen after 5 years despite successful treatment. Therefore, close follow-up of patients for at least 2 years is mandatory.

Author Contributions

TT: review and editing, HET: data collection, Writing ÖO: statistics, ŞMA: conception and design, GT: review and editing, EA: data collection.

Funding

The authors received no financial support for the research and/or authorship of this article.

Data availability

The data is available in Figshare with the identifier 10.6084/m9.figshare.26984662.

Declarations

Conflict of Interest

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Ethical Approval

The ethical approval obtained for conducting this study from Gazi University Ethics Committee the approval number no: E-77082166-604.01.02-730786, the approval date 27.07.2023.

Informed Consent

There is no information (names, initials, hospital identification numbers, or photographs) in the submitted manuscript that can be used to identify patients.