Elemental bio-imaging of melanoma in lymph node biopsies.

The spatial distribution of trace elements in human lymph nodes partially infiltrated by melanoma cells was determined by elemental bio-imaging. Imaging of (31)P within the nodal capsule and normal lymph node tissue showed a clear demarcation of the tumour boundary, with a significant decrease in relative (31)P concentration within the tumour. The location of the tumour boundary was confirmed by haematoxylin and eosin staining of serial sections and observation by light microscopy. Further enhancement of the tumour boundary was achieved by imaging the (31)P/(34)S ratio. (31)P/(66)Zn ratio images showed a decreasing ratio beyond the tumour boundary that extended into peritumour normal lymph node tissue.