Reoperative Selective Sentinel Lymphadenectomy Combined With Lymphoscintigraphy Is Technically Feasible for Cutaneous Tumors of the Upper Extremity After Radical Dissection of Regional Lymph Node Basins for Breast Cancer

DISCUSSION

The primary purpose of this study was to demonstrate that SSL is technically feasible for patients whose predicted drainage basin had previously undergone radical lymphadenectomy. All 7 patients successfully underwent the procedure with the detection of radioactive lymph nodes. The presence of metastatic disease in 2 SLNs from 1 of the 7 patients is proof of principle—that in the presence of potentially altered lymphatics the SLN concept is valid in at least that radiotracer and metastases can follow the same pattern. It also demonstrates that careful, radioguided dissection is safe and can identify residual lymph nodes in a previously dissected axilla. What this study does not address is whether or not SSL has a similar reliability for staging. That 5 of the 6 patients with identified SLNs had SLNs negative for metastasis is certainly not unexpected; however, this study is underpowered to generate any reliable conclusion as to whether or not the false-negative rate should be similar to that which is reported in the literature.

The preoperative hypothesis was that lymphoscintigraphy would either reveal alternative lymphatic drainage pathways and basins (eg, supraclavicular nodes) or drainage via residual axillary nodes. The findings of both alternative pathways (eg, internal mammary nodes) as well as drainage to previously dissected axillae brings up several important considerations—including whether or not there is a “standard” postaxillary dissection lymph node pattern and if under these conditions SSL is accurate in predicting regional nodal metastasis.

The lymphatic drainage to the axilla after dissection has not been fully studied. Most investigation has centered on patients with breast cancer–related lymphedema. Stanton et–al^8,9 have studied (via lymphoscintigraphy) the drainage of the upper extremity after ALND in the subset of patients with postoperative lymphedema. In one study, 24 patients with postoperative lymphedema without hand edema were injected with radiolabeled IgG in the hand; the nonoperated arm was used as the control.¹⁰ No axillary lymph nodes were detected on the edematous, operated side. Furthermore, it appeared that there was increased lymphatic drainage along alternative routes, including the superficial tissues of the forearm and upper arm when compared with controls.

In a different study, fluorescence microlymphography revealed superficial lymphangiogenesis in patients with lymph edema.¹¹ When contrasted with controls who had undergone ALND for breast cancer not complicated lymphedema, new lymphatics were shown to form only in those with lymphedema. This is confirmed by another study that demonstrated that dermal lymphangiogenesis occurs only in patients with postdissection lymphedema. Unfortunately, these and other studies do not provide a comprehensive understanding of axillary drainage after ALND, particularly in those patients not complicated by lymphedema. However, it underscores the potential for alternative drainage patterns to the axilla in the presence of lymphedema.

Of all the observations mentioned earlier, probably the most important is that lymphoscintigraphy is an important tool for preoperative planning. With a multitude of possible drainage patterns, the data suggest that the use of isosulfan blue alone may be inadequate. Even radiocolloid injection and use of only the handheld gamma counter may similarly be inadequate as precise visualization of the SLN is not possible—potentially leading to incision over a “hot spot” in the supraclavicular area only to find that the node detected was high (level III) in the axilla. The opposite (inadvertently opening the previously dissected axilla) is possible and is potentially worse—risking injury to the vital structures in the axilla scarred by previous ALND. Lymphatic mapping avoids these problems by giving a pictorial representation of the SLN's anatomic position in several planes.

In the patients presented here, alternative drainage was present in 2 of the 7 patients. Lymphatic mapping was extremely useful for preoperative planning of all cases. It would be interesting to know whether or not lymphedema was present in any of these patients, but because of the retrospective nature of this study, these data were not available.

Although the patient numbers in this study are limited, SSL is demonstrated to be feasible for patients whose cancer has previously been treated with ALND. In these cases where the dissected axilla is an anticipated drainage basin, alternative lymphatic drainage pathways should be considered. Preoperative lymphoscintigraphy can be helpful in delineating the location(s) of the SLNs in these complicated cases and can guide the surgical plan. It is not clear from our study if the lymphatic drainage through a previously dissected axilla represents de novo lymphatic formation or residual lymph channels. There is evidence of lymphatic growth in humans following ALND (Stanton et al) with lymphedema. Although the complex interplay of cytokines responsible for lymphangiogenesis has been well defined in animal models, that understanding has yet been translated into human medicine.¹² In patients with previous ANLD, we cannot exclude either the possibility of lymphangiogenesis or of residual lymphatics. Unraveling the complexity of these drainage patterns in patients with previous ALND requires lymphoscintigraphy as a helpful means of identifying SLNs. Additional study will be needed to further validate these conclusions.