The purpose of the study is to check how safe and well-tolerated [18F]LY4214835 injection is in healthy participants and participants with cancer. The study drug will be administered intravenously (IV) (into a vein). Participation in the study will last approximately 35 days.

Inclusion Criteria:

• Cohort 1

  • Have a radiologically, cytologically, or histologically confirmed diagnosis of cancer
  • Are treatment-naïve to a systemic cancer therapy, OR have a documented disease progression on standard-of-care treatment (for example, failure of chemotherapy, targeted therapy or immunotherapy)
  • Have at least 1 imageable tumor that is 15 millimeter (mm) or larger in the longest diameter

• Cohort 2

  • Are overtly healthy at the Screening Visit and upon reporting to the clinic for the positron emission tomography (PET) Imaging Visit, as determined by medical evaluation including updated medical history, vital signs, physical examination, laboratory tests, and electrocardiogram (ECG)

Exclusion Criteria:

• Are pregnant or intend to become pregnant during their participation in the study
• Are breastfeeding or intending to breastfeed during their participation in the study
• Have a history of risk factors for Torsades de Pointes (for example, heart failure, hypokalemia, family history of Long QT Syndrome)
• Are actively receiving cancer therapy or are in between cycles of treatment
• Have a marked baseline prolongation of QT/corrected QT interval (QTc) interval (for example, repeated demonstration of a QTc interval greater than (>) 450 millisecond (ms)