SENTINEL LYMPH NODE TECHNIQUE

Lymphogammagraphy has proved to be very useful in the study of the lymphatic drainage of melanomas. The concept of sentinel lymph node has been developed to diminish morbility produced by lymphadenectomy.

The sentinel lymph node is the first situated in the drainage lymphatic via of a tumour.

It is assumed that if the lymph node is free, so are the following ones, which makes posterior surgical interventions unnecessary in the lymphatic via.

At the Nuclear Medicine Department:

We administer a dose of colloid marked with Tc99M, in several peritumoral injections.

With a gammacamera we check the migration of the radiocolloid until the first or first lymph nodes appear. If there is more than one we choose the one that captures the most. We localise it through cutaneous marks.

At the operating Theatre:

Through a portable detector, wrapped in a sterile covering, we determine which one presents the highest activity in the biopsy slit and we extract what we consider the sentinel lymph node.

At the Pathology Department:

1.- Reception:

1.1.- The removed tissue must immediately be sent to the Pathology Department. The tissue must be fresh, if you wish intraoperatory study or manipulation previous to the fixation, with a clear determination of the sentinel lymph node.

1.2.- The tissue can be introduced straight into formol, without sectioning, carrying out a minimum fixation of 24h for posterior processing, with a clear reference of the sentinel lymph node in the conta.

2.- Macroscopic:

2.1.- The lymph node/s must be identified and their maximum diameter must be written down.

2.2.- We carry out cuts every 2mm and we include the total number of them.

3.- Technical processing:

3.1.- We do sections with 6 lamellas, the first three contiguous, the fourth at 100 micras, the fifth contiguous and the sixth at 200 micras.

3.2.- They are dyed according to the following sequence:1st HE, 2nd HMB-45, 3rd S-100, 4th HE, 5th HMB-45, 6th HE.

4.- Microscopic:

4.1.- The result is defined as positive or negative. 4.2.- In case of a positive result with IH we assess if the cellular group is smaller than 10 cells ("hidden tumoral cells") or bigger than 10 cells ("hidden tumoral colonies"). 4.3.- If there were any problems or doubts we can section the rest of the ganglionar tissue.