Incidental Breast Cancer Diagnosis From Lymphoscintography Using 99mTc-Labeled Nanocolloid for Cutaneous Melanoma of the Upper Arm.

A 51-year-old woman with a 2-mm-Breslow-thickness melanoma on her arm had 99mTc-nanocolloid lymphoscintigraphy to localize the associated sentinel lymph node. A single axillary node was identified, and histology confirmed a micrometastasis of breast tissue origin. Imaging of the patient's breasts and subsequent biopsy confirmed ipsilateral stage III breast cancer, which was treated with lumpectomy and axillary node clearance. This is the first reported case of an incidental solid cancer diagnosis from a sentinel lymph node biopsy undertaken for a different tumor origin. This illustrates the importance of recognizing overlapping lymphatic distribution of sentinel lymph nodes, which can drain multiple organs.