This is a two-part study of pembrolizumab (MK-3475) in pediatric participants who have either advanced melanoma, relapsed or refractory classical Hodgkin lymphoma (rrcHL) or advanced, relapsed or refractory programmed cell death ligand 1 (PD-L1) positive malignant solid tumor or other lymphoma. Part 1 will find the maximum tolerated dose (MTD)/maximum administered dose (MAD), confirm the dose, and find the recommended Phase 2 dose (RP2D) for pembrolizumab therapy. Part 2 will further evaluate the safety and efficacy at the pediatric RP2D. This study is being sponsored by the Children's...