Popliteal lymph node dissection for metastatic squamous cell carcinoma: a case report of an uncommon procedure for an uncommon presentation
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Lymph node metastasis from cutaneous squamous cell carcinoma is uncommon. The popliteal fossa is rarely involved with metastasis. Popliteal lymph node dissection is uncommonly performed and not frequently discussed in the literature. We present a case of squamous cell carcinoma of the heel with popliteal and inguinal metastasis. This is followed by a description of the relevant anatomy of the popliteal fossa and the technique of popliteal lymphadenectomy.
KeywordsSquamous cell carcinoma Popliteal metastasis Popliteal dissection
Regional lymph node (LN) metastasis is an important prognostic factor for skin cancers like melanomas and squamous cell carcinomas (SCC) . The usual nodal basins involved are the cervical, axillary and inguinal regions. However, metastasis can involve other areas, like the epitrochlear and popliteal regions. The use of preoperative lymphoscintigrapy (LS) has allowed the detection of interval or in-transit LN, which can also be involved with metastatic disease .
Skin cancers of the lower limb below the knee mainly metastasise to the groin. Metastasis to the popliteal LN is much less common. In melanoma, the incidence of popliteal metastasis ranges from 0.3% to 7% [2, 3, 4]. For SCC the incidence is not known, but appears to be less than these figures. Lymph nodes in this region should be managed as those in any other nodal basin. They should be looked for, and if involved, they should be resected. Due to the fact that popliteal node metastasis is uncommon and that many surgeons lack the experience in popliteal dissection, this issue is infrequently discussed in the literature. The wider adoption of sentinel lymph node (SLN) biopsy for skin cancer is causing more surgeons to deal with LN in this region. We present a case of SCC with popliteal LN metastasis. This is followed by a review of the relevant anatomy and the surgical technique of popliteal lymphadenectomy.
In 2008, a 41-year-old lady developed an ulcer on her left heel. This was excised by a general surgeon at another hospital. Pathological examination revealed a 3.8 cm, moderately differentiated SCC; the margins were involved. No further treatment was offered to the patient. A year later, in June 2009, the tumor recurred and was excised again; the margins were negative this time.
Popliteal lymph node dissection
In general there are 2 steps to popliteal LN dissection. The first step is adequate exposure of the diamond shaped fossa. This should include careful identification and preservation of the neurovascular structures. Once that is done, dissection of the fat pad should be performed thoroughly.
Subsequently, the popliteal fossa is entered by opening the popliteal fascia vertically in the midline. The first structure to appear is the Tibial nerve, which crosses vertically and disappears between the 2 heads of Gastrocnemius. Lateral to it is the Peroneal nerve, which courses laterally along the biceps femoris tendon and then turns obliquely towards the fibula. Both nerves should be retracted laterally with vessel loops to allow adequate and safe exposure of the vessels and the LNs. Dissection deep to the Tibial nerve will reveal the popliteal vein. The popliteal artery passes deep and slightly medial to the vein. It is the deepest structure in the popliteal fossa and lies on the femur and capsule of the knee joint. The LNs are contained within the fatty tissue that is found superficial, alongside and deep to the popliteal vessels. LN dissection should include, therefore, all the fatty tissue in the popliteal fossa till reaching the posterior aspect of the knee joint. It should be noted that the popliteal fossa is wider in the deeper part than in the superficial part. Adequate retraction of the Gastrocnemius muscle heads, therefore, is essential to ensure adequate exposure and dissection of all the LNs.
After securing hemostasis, the fascia is approximated and the wound is closed over a negative suction drain. A knee splint or back slab is preferably applied at this stage and left in for the first few postoperative days. Postoperative Lymphoedema is expected in some patients . The incidence of lymphoedema is expected to increase dramatically with the addition of inguinal dissection and or radiotherapy.
We describe an unusual case. The incidence of LN metastasis from SCC is relatively uncommon. It ranges from 0.5% to 16% , with most series reporting a rate of < 5% . Usually this occurs in tumors with poor prognostic factors such as larger size, poor differentiation, presence of perineural invasion or recurrent tumors. Popliteal metastasis is quite rare. In a series of 1, 118 patients, with localized squamous cell carcinoma of the extremity, treated at M.D. Anderson Hospital and Tumor Institute in Houston, Texas, only 16 patients (1.4%) developed recurrence . Of the 106 treated patients who had regional or distant metastasis, only 2 patients had popliteal metastasis, and both had inguinal metastasis as well.
Although SLN biopsy is mainly indicated for melanomas, it is gaining wider application in the management of other skin tumors, like SCC . Still, the indications for SLN biopsy in SCC are not clear. Its' use in lower extremity tumors will allow the detection of more patients with popliteal LN metastasis, many of those will probably be micrometastases.
The procedure of popliteal lymphadenectomy was first described by Karakousis in 1980. Most later descriptions are based on it. Knowledge of the relevant anatomy and the surgical technique of popliteal LN dissection is important to avoid injury to important structures and to allow adequate LN dissection.
Popliteal metastasis from skin SCC is quite uncommon. It usually occurs in patients with advanced or recurrent tumors. Appropriate management is not clear, but surgical dissection, in the absence of distant metastasis, is indicated since there is no known effective adjuvant treatment for skin SCC.
Written informed consent was obtained from the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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