The hidden sentinel node and SPECT/CT in breast cancer patients.

Purpose: In a minority of breast cancer patients, lymphoscintigraphy shows no lymphatic drainage and 'hidden' sentinel nodes may remain undiscovered. The purpose of this study was to explore the additional value of the recently introduced hybrid SPECT/CT in breast cancer patients with axillary non-visualisation on planar images. The role of blue dye and careful palpation of the axilla was evaluated in patients in whom axillary sentinel nodes remained hidden after SPECT/CT.

Methods: Fifteen breast cancer patients with non-visualisation on planar lymphoscintigraphy and 13 women with only extra-axillary sentinel nodes underwent SPECT/CT following late planar imaging without re-injection of the radiopharmaceutical.

Results: SPECT/CT visualised lymphatic drainage in eight of the 15 patients (53%) with non-visualisation on planar imaging, depicted nine of the 14 harvested sentinel nodes (64%) and three of five tumour-positive sentinel nodes. In two of the 13 patients (15%) with only extra-axillary sentinel nodes on their planar lymphoscintigram, SPECT/CT showed an axillary sentinel node that appeared to be uninvolved. Careful exploration of the axilla with the combined use of blue dye, a gamma probe and intra-operative palpation revealed an axillary sentinel node in the remaining 18 patients. SPECT/CT showed the exact anatomical location of all visualised sentinel nodes.

Conclusion: SPECT/CT discovered 'hidden' sentinel nodes in the majority of patients with non-visualisation, but was less valuable in patients with only extra-axillary lymphatic drainage on the planar images. Exploration of the axilla in patients with persistent non-visualisation improved the identification of axillary (involved) sentinel nodes.