Patients undergo routine sentinel lymph node procedure (99mTc injection, planar imaging, SPECT-CT and surgery) for clinical purposes. After 99mTc injections and imaging has been executed peritumoral SPIO injections are performed by a medical doctor. A T2*-weighted iron sensitive MRI scan is made 1 hour later.

SPIO is peritumorally injected. A T2*-weighted iron sensitive MRI scan is performed 1 hour later to localize and assess the sentinel lymph nodes.

The first two patients will receive a dose of 0.012 ml SPIO. MR-images will be assessed. If this dose provides satisfactory MR-images (good visualization of lymph nodes without disturbing artefacts), subsequent patients will receive the same dose. If the artefact is too large, the dose will be decreased. If visualization is poor, the dose will be increased. The procedure will be repeated with adjusted doses each time in two patients until satisfactory MR-images are obtained.

The investigators have established timing of MRI 1 hour after SPIO injection. It is assumed that after this time interval SPIO particles have had sufficient time to migrate to the SNs and to be taken up. However, if this interval appears to be too long because 'too many' SNs are visualized the time interval will be shortened. If this interval appears to be too short since no or too little SNs are visualized because SPIO uptake has not taken place yet, the time interval will be lengthened.

SPIO-enhanced MR-images and SPECT-CT images are compared to investigate whether SPIO-enhanced MRI detects the same sentinel lymph nodes as SPECT-CT.