Lymphatic Mapping Of The Skin

The first comprehensive descriptions of the lymphatic drainage of the skin were based on the elegant work of the anatomist Sappey, who in the nineteenth century injected mercury into the lymphatics of cadavers to display the lymph channels [3,4]. He reported drainage to the axilla and groin from the skin of the trunk (Figs. 1-3) and showed a vertical midline zone anteriorly and posteriorly where drainage tended to overlap. A similar zone was identified passing horizontally around the waist from the umbilicus to the region of the second lumbar vertebra posteriorly. In these zones, called ''Sappey's lines'' by others, drainage was said to be possible to either side in the case of the vertical zone or to either the groin or the axilla in the case of the horizontal zone. Outside these zones, however, Sappey stated that lymphatic drainage was always to the ipsilateral groin or axilla, depending on whether the skin site of interest was above or below the horizontal band around the waist.

In the early 1950s, Walker was the first to use radiotracers to map lymphatic drainage [5]. Following this, Sherman et al. developed the concept of lymphoscintigraphy [6], demonstrating that colloidal gold could be traced from the point of intradermal injection to the draining lymph nodes. This was the advent of cutaneous lymphoscintigraphy as we know it today. Initially, colloidal gold-198 (198Au) was used. This tracer has a very small particle size of about 5 nm. The disadvantage of colloidal 198Au is that it is a beta emitter and thus tissues around the site of injection receive a high radiation dose. Technetium-99m (99mTc)-labeled colloids were developed to deal with this problem.

Sappey Lymphatic
Figure 1 Lymphatics draining to groin lymph nodes. (From Ref. 4.) The Zones of Ambiguity

Sappey's concept of the lymphatic drainage of the trunk was accepted as correct for 130 years until modified somewhat by Haagensen et al. [7], who enlarged the ambiguous zone to a 5-cm band down the midline and around the waist. Sugarbaker and McBride confirmed that drainage was ambiguous from these areas, but it continued to be thought that lymph drainage from skin of the trunk outside these ambiguous zones would be predictable to the axilla or groin [8].

Colloidal 198Au was used by Fee et al. in 1978 when they studied 32 patients with melanoma [9]. This study confirmed that lymphoscintigraphy could accurately predict the node fields that potentially contained metastatic melanoma.

Lymph Node Map
Figure 2 Lymphatics draining to the axillary lymph nodes. (From Ref. 4.)
Lymph Node Drained Field

Nine of their patients had nodal metastases, and in every case, lymph drainage from the primary site to this node field was demonstrated on lymphoscintigraphy. Around this time, other investigators were also using scintigraphy to map lymph drainage in patients with melanomas located on the trunk and elsewhere when drainage was considered uncertain (i.e., in Sappey's zones of uncertainty or in the head and neck [10,11]). It was emphasized that lymphoscintigraphy could not predict whether lymph nodes contained metastases, but that it could identify which node fields were at greatest risk of harboring occult metastases [12].

More studies began to appear which expanded the zone of uncertainty around Sappey's lines and also demonstrated that drainage in the head and neck was quite variable [13]. The results of lymphoscintigraphy began to be used as a guide to determine which lymph node fields were to be subjected to elective lymphadenectomy [14-16]. It also became increasingly apparent that drainage could sometimes be identified with node fields, which would not be considered potential metastatic sites on clinical grounds [17].

For many years, cutaneous lymphoscintigraphy was thus used to identify which node fields received lymphatic drainage from the primary melanoma site on the skin and, therefore, which node fields were potential sites of occult metastases. With experience, it became clear that lymphoscintigraphy should be performed before wide local excision or lymphadenectomy, as it was shown that these procedures disrupted the normal lymphatic drainage pathways [18,19]. As such studies proceeded, the zones of ambiguity on the trunk and elsewhere were continually expanded as more and more exceptions to the expected patterns of lymphatic drainage were demonstrated [20,21]. Nevertheless, lymphoscintigra-phy continued to be performed only when some clinical doubt was present about the pattern of drainage. The threshold of doubt varied considerably from surgeon to surgeon, with the end result that there was considerable variation in the sites subjected to lymphadenectomy by different surgeons for lesions at the same site on the skin. Lymphoscintigraphy was not performed if the primary site was on a limb or close to an individual node field.

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  • nadia palerma
    Where are the lymph noteds?
    8 years ago

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