Testing a New Imaging Agent to Identify Cancer

The purpose of this study is to see whether 89Zr-ss-pertuzumab is safe in people with HER2+ cancer.

Inclusion Criteria: * Biopsy proven HER2-positive or HER2-low primary malignancy or metastatic disease Note: HER2 positivity is defined according to American Society of Clinical Oncology guidelines or ERBB2 amplification on next generation sequencing Note: HER2-low is defined as low HER2 expression, with immunohistochemistry (IHC) 1+ or IHC 2+ and in situ hybridization \[ISH\]-negative, including FISH. * Biopsy proven primary malignancy or metastatic disease * At least one malignant lesion on CT, MR, or FDG PET/CT within 60 days of protocol enrollment * Age 18 years or greater * ECOG performance of 0-2 Exclusion Criteria: * Creatinine \> 2 times normal limit (obtained with 8 weeks of enrollment) * AST/ALT \> 2 times normal limit (obtained with 8 weeks of enrollment) * Life expectancy \< 3 months * Pregnancy or lactation * Patients who cannot undergo PET/CT due to weight limits (over 450 pounds)