Figure 1.

This is a 43-year-old female with left breast invasive ductal carcinoma (ER+, PR+, and HER2−) and metastases to the left supraclavicular, thoracic, and retroperitoneal nodes and left adrenal gland. She was on everolimus and exemestane at the time of ⁸⁹Zr-trastuzumab PET/CT. Tracer avidity was visualized in a known left adrenal metastasis (blue arrow), with SUVmax 9.2. Additional FDG-avid left supraclavicular, thoracic, and retroperitoneal nodes were not tracer avid on ⁸⁹Zr-trastuzumab PET/CT (green arrows), suggesting lack of HER2 expression and HER2 intertumoral heterogeneity of metastatic lesions.