Unresectable or metastatic melanoma; adjuvant treatment of melanoma with lymph node involvement after complete resection; first-line treatment in combination with pemetrexed and platinum chemotherapy for metastatic nonsquamous non–small-cell lung cancer (NSCLC), with no EGFR or ALK genomic tumor aberrations; first-line in combination with carboplatin and either paclitaxel or paclitaxel protein-bound for metastatic squamous NSCLC; first-line, single agent for NSCLC expressing PD-L1 as determined by an FDA-approved test, with no EGFR or ALK genomic tumor aberrations, and is stage III where patients are metatstatic or not candidates for surgical resection or definitive chemoradiation; monotherapy for metastatic NSCLC whose tumors express PD-L1 as determined by an FDA-approved test, with disease progression on or after platinum-containing chemotherapy; first-line in combination with platinum and fluorouracil for metastatic or unresectable, recurrent head and neck squamous-cell carcinoma; first-line, single agent for metastatic or unresectable, recurrent head and neck squamous-cell carcinoma whose tumors express PD-L1 as determined by an FDA-approved test; monotherapy for recurrent or metastatic head and neck squamous-cell carcinoma with disease progression on or after platinum-containing chemotherapy; relapsed or refractory classical Hodgkin lymphoma in adult patients; refractory classical Hodgkin lymphoma, or classical Hodgkin lymphoma that has relapsed after 2 or more lines of therapy in pediatric patients; refractory primary mediastinal B-cell lymphoma in adult and pediatric patients who have relapsed after 2 or more prior lines of therapy; locally advanced or metastatic urothelial carcinoma in patients who are not eligible for cisplatin-containing chemotherapy, or locally advanced or metastatic urothelial carcinoma in patients who have disease progression during or following platinum-containing chemotherapy or within 12 months of neoadjuvant or adjuvant treatment with platinum-containing chemotherapy; Bacillus Calmette-Guerin (BCG)-unresponsive, high-risk, non–muscle-invasive bladder cancer with carcinoma in situ with or without papillary tumors in patients who are ineligible for or have elected not to undergo cystectomy; for the treatment of adult and pediatric patients with unresectable or metastatic, microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) solid tumors that have progressed following prior treatment and who have no satisfactory alternative treatment options; unresectable or metastatic MSI-H or dMMR colorectal cancer; first-line in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy for locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction (GEJ) adenocarcinoma; single agent for the treatment of patients with recurrent locally advanced or metastatic gastric or GEJ adenocarcinoma whose tumors express PD-L1 as determined by an FDA-approved test, with disease progression on or after 2 or more prior lines of therapy, including fluoropyrimidine- and platinum-containing chemotherapy and, if appropriate, HER2/neu-targeted therapy; locally advanced or metastatic esophageal or GEJ carcinoma that is not amenable to surgical resection or definitive chemoradiation either in combination with platinum- and fluoropyrimidine-based chemotherapy or as a single agent after 1 or more prior lines of systemic therapy for patients with tumors of squamous-cell histology that express PD-L1 as determined by an FDA-approved test; recurrent or metastatic cervical cancer with disease progression on or after chemotherapy whose tumors express PD-L1 as determined by an FDA-approved test; hepatocellular carcinoma in patients who have been previously treated with sorafenib; recurrent locally advanced or metastatic Merkel-cell carcinoma in adult and pediatric patients; first-line in combination with axitinib for advanced renal-cell carcinoma in adult patients; first-line in combination with lenvatinib for advanced renal-cell carcinoma; in combination with lenvatinib, for advanced endometrial carcinoma that is not MSI-H or dMMR, for patients who have disease progression following prior systemic therapy in any setting and are not candidates for curative surgery or radiation; adult and pediatric patients with unresectable or metastatic tumor mutational burden-high solid tumors, as determined by an FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment options; recurrent, metastatic, or locally advanced cutaneous squamous-cell carcinoma that is not curable by surgery or radiation; high-risk early-stage triple-negative breast cancer in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery; locally recurrent unresectable or metastatic triple-negative breast cancer in combination with chemotherapy, where tumors express PD-L1 as determined by an FDA-approved test