10.1245/ASO.2005.05.009
Annals of Surgical Oncology 12:189-193 (2005)
© 2005 Society of Surgical Oncology
Popliteal Lymph Node Dissection
Alina Sholar, MD,
Robert C. G. Martin, II, MD and
Kelly M. McMasters, MD, PhD
Department of Surgery, Division of Surgical Oncology, University of Louisville, James Graham Brown Cancer Center, 315 E. Broadway, Suite 308, Louisville, Kentucky 40202
Correspondence: Address correspondence and reprint requests to: Kelly M. McMasters, MD, PhD; E-mail: kelly.mcmasters{at}norton-healthcare.org.
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ABSTRACT
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Most sentinel nodes are located in the cervical, axillary, and inguinal nodal basins. Sometimes, however, sentinel nodes exist outside these traditional nodal basins. Popliteal nodal metastasis is relatively uncommon, and popliteal lymph node dissection is infrequently necessary. However, with lymphoscintigraphic identification of popliteal sentinel nodes, surgeons are more frequently called on to address the popliteal nodal basin. Therefore, knowledge of the anatomy and surgical technique for popliteal lymphadenectomy is essential. This case study illustrates the importance of considering the approach to the popliteal lymph node basin for patients with melanoma.
Key Words: Sentinel lymph node • Lymphadenectomy • Lymph node dissection • Melanoma • Interval nodes • In-transit nodes
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INTRODUCTION
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With detailed preoperative lymphoscintigraphy, it is possible to determine the precise regional nodal drainage patterns for patients with cutaneous melanoma. This, coupled with intraoperative lymphatic mapping with blue dye and a handheld gamma probe, allows identification and removal of the first-draining, or sentinel, nodes. Although anatomical predictions of nodal drainage are not always reliable, most sentinel nodes are located in the cervical, axillary, and inguinal nodal basins. Sometimes, however, sentinel nodes exist outside these traditional nodal basins—including drainage to the epitrochlear and popliteal nodes for distal upper and lower extremity lesions, respectively. Popliteal nodal metastasis is relatively uncommon, and popliteal lymph node dissection is infrequently necessary. However, with lymphoscintigraphic identification of popliteal sentinel nodes, surgeons are more frequently called on to address the popliteal nodal basin. Therefore, knowledge of the anatomy and surgical technique for popliteal lymphadenectomy is essential, yet there are few published reports regarding the technique of popliteal lymph node dissection.1–4 This case study illustrates the importance of considering the approach to the popliteal lymph node basin for patients with melanoma.
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CASE REPORT
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A 52-year-old woman presented to a general surgeon with a 1-year history of an enlarging melanotic lesion of her right heel. A podiatrist had previously treated it as a plantar wart with acetic acid for 4 to 5 months. She was fair skinned and had a few sunburns as a child; she had no history of skin cancer, but her father had also had melanoma treated, without recurrence. Finally, 8 months after she first noticed the lesion, she underwent excisional biopsy of the lesion, which, on pathologic examination, was confirmed to be a 4.5-mm-thick, nonulcerated melanoma (Clark’s level IV). Wide local excision with a 2-cm margin was then performed, along with sentinel lymph node biopsy. Preoperative lymphoscintigraphy showed two separate lymph channels draining to two nodes in the popliteal fossa and then showed delayed uptake of radiotracer in one node in the groin (Fig. 1
). The inguinal sentinel node was removed and was found on final pathology to be positive for metastatic melanoma. The surgeon did not remove the popliteal sentinel nodes identified by the lymphoscintigram. Completion superficial inguinal lymph node dissection was performed, and this revealed 9 of 15 positive lymph nodes. Despite the presence of multiple positive superficial inguinal nodes, an iliac/obturator lymphadenectomy was not performed, although computed tomographic scans at that time did not demonstrate evidence of macroscopic nodal disease in the abdomen or pelvis. The patient had an unremarkable postoperative recovery except for mild to moderate lymphedema and went on to receive adjuvant therapy with high-dose interferon alfa-2b.
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FIG. 1. Popliteal and inguinal lymphoscintigraphy. (A) Lymphoscintigraphy identifies the location of two popliteal sentinel nodes (arrows). (B) Two separate lymphatic channels are seen. (C) Lateral views can give an indication of the depth of the lymph nodes relative to the skin, because some interval nodes can be subcutaneous or superficial. Arrow indicates location of inguinal nodes.
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She did not return for a scheduled follow-up appointment initially but finally presented to a different surgeon approximately 17 months later. On reviewing the patient’s medical records, this surgeon recognized the popliteal sentinel nodes, which had not been addressed previously. Positron emission tomography scan revealed evidence of nodal metastasis in the right iliac chain and persistent nodal disease at the right posterior knee. This was followed by magnetic resonance imaging to evaluate the anatomy of the nodal basin of the popliteal space. This revealed two grossly enlarged nodes as well (Fig. 2).
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FIG. 2. Magnetic resonance image of the right popliteal space. (A) Sagittal view showing an abnormal lymph node anterior to the popliteal vessels (arrow). It is important to recognize that 1 or 2 nodes may exist in this location. (B) Sagittal view showing a more superficial node that is abnormally enlarged (arrow). (C) Axial view showing the node (arrow) seen in panel B. (D) Coronal view demonstrating the enlarged node (arrow) seen in panel A.
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The next step was a popliteal node dissection. All nodes in the dissection specimen were diffusely replaced by melanoma (three nodes); each measured >2 cm in diameter. The patient also underwent concomitant iliac and obturator lymph node dissection because of recurrent disease in that location as well, with 8 of 13 positive nodes. All wounds healed in a satisfactory fashion, without excessive scarring or contracture of the posterior knee crease. A medical oncologist was consulted for subsequent systemic treatment options. She was also referred for radiation treatment to the right groin and popliteal space because of the presence of bulky nodal disease and extracapsular extension. The patient, predictably, developed worse lymphedema of the right lower extremity. This was treated by compression stocking and massage therapy, although she remained ambulatory without assistance.
In 1980, Karakousis1 published an elegant and detailed description of popliteal lymph node dissection that remains the seminal report on this procedure. He used a long sigmoid-shaped incision with the horizontal portion across the posterior crease of the knee. Our technique differs somewhat from his in the incision and exposure. The patient is placed prone with the knee slightly flexed. A Z-plasty incision is made over the flexor crease to, first, allow for optimal exposure, and, second, heal in a manner not to cause a deforming joint contracture (Fig. 3). The width and length of the Z is judged by the caliber of the lower thigh, usually with an interior angle of approximately 100° to 120°. After the incision is created and carried down through the subcutaneous tissue, lateral and medial flaps are raised while traction is maintained with skin hooks. As the fascia is exposed, the most superficial structures that come in to view are the lesser saphenous vein and some small cutaneous nerve terminal branches (Fig. 3). At this point, the lesser saphenous vein must be ligated and divided. Next, the deep fascia is incised vertically, with care not to damage structures below the fascia, because the nerves are quite superficial (Fig. 4). If the medial sural nerve can be retracted out of the way, it should be. However, if need be, it can be divided to gain better access to deeper structures; this will result in cutaneous anesthesia. The tibial nerve is the most superficial midline structure. This is very gently retracted laterally with a vessel loop. Likewise, the peroneal nerve courses along the biceps femoris tendon and then obliquely turns more laterally toward the fibula. The superior extent of the dissection is bounded by the intersection of the biceps femoris and semimembranosus muscles. Inferiorly, the two heads of the gastrocnemius muscle can be further retracted as well to enhance distal exposure. A fat pad overlying and alongside the popliteal vessels is reported to encase six to seven lymph nodes,1 although our experience and that of others suggests that fewer nodes may be encountered (Fig. 4) (Delman et al., unpublished data). It is important to recognize that one lymph node is frequently located anterior to the artery and posterior to the knee joint. The popliteal vessels are ensheathed, and the popliteal artery is slightly medial and deeper to the vein. The popliteal vein has variable small tributaries below the level of the lesser saphenous vein branch of which the surgeon should be mindful.
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FIG. 3. Right popliteal node dissection. Z-incision of the posterior right knee (left) and exposure of superficial structures (fascia) (right). v, vein; Post., posterior.
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FIG. 4. Exposure of the right posterior knee: popliteal vessels and tibial nerve, with a deeper view of the dissection.
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The popliteal space can be palpated to identify any obviously abnormal nodes. In the patient presented, the nodes seen on magnetic resonance imaging were easily palpable but could easily have been missed on casual inspection. With careful sharp dissection, the fat pad and lymphatic tissue are removed in continuity superficial to, beneath, and alongside the vessels and nerves. Once this is completed, the space should be reevaluated by inspection and palpation to ensure that all lymphatic tissue is excised. At this point, hemostasis should be meticulous. The deep fascia is then reapproximated with a running 2-0 absorbable suture. The skin is then closed in the usual manner over a closed suction drain. A posterior knee splint, or knee immobilizer, is applied for the first few postoperative days to allow healing before the patient returns to full ambulation.
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DISCUSSION
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Lymphoscintigraphy is used more often now for sentinel lymph node biopsy and sometimes identifies popliteal nodal drainage, which can be the only site of nodal metastasis in some cases. It is therefore important to perform preoperative lymphoscintigraphy even for distal extremity lesions and to remove all sentinel nodes identified by the lymphoscintigram. Furthermore, although the indications for iliac/obturator lymph node dissection are debated, many believe that the presence of multiple positive superficial inguinal nodes is an appropriate indication for performing the deep nodal dissection. This case illustrates the difficult problem of regional disease control that can occur when lymphadenectomy of all affected nodal basins is not performed. Certainly, completion lymph node dissection for patients with microscopically positive sentinel nodes seems to provide much better regional disease control compared with lymph node dissection performed for bulky nodal disease.5 Whether the extent of lymphadenectomy ultimately affects survival remains an unanswered question.
Before the advent of sentinel lymph node biopsy, metastasis to the popliteal nodes from lower leg melanomas was an unusual finding unless the nodes were very bulky. Because lymph nodes in the popliteal space lie beneath a thick fascial layer, they are not easily palpable. With observation of lymphoscintigrams of >4000 patients with primary cutaneous melanomas occurring distal to the knee, Thompson et al.2 demonstrated that there were significantly fewer positive nodes in the popliteal fossa than expected. However, if a node in the popliteal fossa is observed on lymphoscintigraphy, then a sentinel lymph node biopsy is indicated. If the specimen is positive for melanoma, a popliteal node dissection, as described, is the logical next step. Thompson et al. concluded that there are two indications for popliteal node clearance: a histologically positive sentinel node in the popliteal fossa or clinical evidence of metastatic disease in this area.
With the increasing use of high-quality lymphoscintigraphy, dissection of the popliteal lymph nodes is more frequently necessary. A working knowledge of the anatomy and technique of popliteal lymph node dissection is therefore required. Although on the surface it may seem to be a trivial procedure to remove a few lymph nodes around the popliteal fossa vessels and nerves, we have found that it is easy to underestimate this procedure. The challenges of popliteal lymphadenectomy are highlighted by a recent report in which a substantial number of patients underwent popliteal lymphadenectomy without removal of a single lymph node (Delman et al., unpublished data). Specifically, attempts to dissect the popliteal lymph nodes through a medial incision (similar to that used for a femoral-popliteal bypass graft) may not allow sufficient exposure to accomplish thorough lymph node dissection. The approach described herein, and as originally described by Karakousis,1 allows better exposure and more thorough dissection.
Received for publication May 10, 2004.
Accepted for publication October 26, 2004.
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REFERENCES
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- Karakousis CP. The technique of popliteal node dissection. Surg Gynecol Obstet 1980;151:420–3.[Medline]
- Thompson JF, Hunt JA, Culjak G, Uren RF, Howman-Giles R, Harman CR. Popliteal lymph node metastasis from primary cutaneous melanoma. Eur J Surg Oncol 2000; 26:172–6.[CrossRef][Medline]
- Georgeu GA, El-Muttardi N, Mercer DM. Malignant melanoma metastasis to the sentinel node in the popliteal fossa. Br J Plast Surg 2002;55:443–5.[Medline]
- Coit DG, Balch CM. Groin and popliteal dissection. Technique and complications. In: Balch CM, Houghton AN, Sober AJ, Soong S-J (eds.). Cutaneous Melanoma. 4th ed. St. Louis: Quality Medical Publishing 2003:4167.
- Chao C, Wong SL, Ross MI, et al. Patterns of early recurrence after sentinel lymph node biopsy for melanoma. Am J Surg 2002;184:520–4.[CrossRef][Medline]
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ABSTRACT
INTRODUCTION
