The Skin

The lymphatic drainage of the skin on the medial side of the scapula could be to the ipsilateral supraclavicular fossa, the ipsilateral axilla, the ipsilateral mid trunk node or indeed it could drain to the contralateral side.

This unpredictability of drainage makes a best guess approach akin to the battleships board game. You may hit the right basin, but then again you may not.

A further problem is the morbidity associated with radical excision of the lymph node basin, in particular the axillary basin, which may result in upper limb lymph-oedema.

Yet another reservation is lack of evidence of benefit to the patient with melanoma from elective lymph node dissection.

However, lymphatic metastases do offer prognostic information. If there is no evidence of lymphatic metastatic disease the patient may be reassured.

For these reasons, sentinal node techniques are becoming attractive. They combine a minimal surgical approach (lower morbidity), with accurate identification of the first draining node (no battleships). The node may be examined pathologically and decisions regarding block dissection made on the basis of the sentinal node result.

It seems however, that the sentinal node technique has introduced new complexities.

• It is not 100% accurate, the surgeon may miss the true first draining node.
• Metastases may skip the first node and be found elsewhere in the basin.
• Absence of lymphatic metastases does not mean that there are no widespread haematogenous metastases.
• With a smaller amount of tissue available the pathologist will examine the sentinal node closer than, she would examine say 30 nodes from a conventional block dissection. This would increase the chance of smaller metastases being detected in the sentinal node, that may have been missed on conventional assessment. Moreover, the pathologist may use adjuvant techniques such as immuno-histochemistry to pick out metastatic cells that are invisible on ordinary haematoxylin and eosin preparations. Both these factors may mean that the significance of such micro-metastases may not be as great as metastases detected on examination of conventional block dissections.