Intracapsular melanoma: a new pitfall for sentinel lymph node biopsy

Sentinel lymph node biopsy (SLNB) has become an established technique for the staging and treatment of cutaneous melanoma. 1, 2 SLNB is very accurate in predicting tumour burden in the remaining regional lymph node basin and is also the most important independent prognostic indicator for recurrence and survival when compared with factors such as tumour thickness and ulceration. 1 Large retrospective studies have shown that positive sentinel lymph nodes (SLNs) contain metastatic foci of melanoma cells in the subcapsular, sinusoidal or parenchymal regions. The subcapsular region is most commonly associated and up to 86% of metastatic foci become seeded in this area. 3 An important caveat of SLNB, however, is the false positives which result from benign naevic cells present in the capsule (intracapsular) or trabeculae of SLNs. 4 It is the intracapsular location of these cells, as well as differences in immunostaining and atypia, that aids the pathologist in distinguishing benign naevic cells from metastatic foci. 3- 5 Indeed, false-positives resulting from benign naevic cells are a cause for concern and require further investigation.