A 43-year-old healthy man complained of constant general fatigue for 11 days. Twenty-two days earlier, the patient received his third dose of the coronavirus disease 2019 vaccine. An electrocardiogram revealed inverted T waves with a wide spectrum of precordial lead, and echocardiography revealed diffuse left ventricular dysfunction, indicating acute myocarditis.

A 73-year-old man underwent a stage Ⅱ sigmoid colon cancer resection. Careful monitoring was undertaken, and no evidence of metastasis or anastomotic recurrence was noted until 51 months later. Anal examination revealed a pink, firm perianal tumor histologically identified as a metastasis of the colon adenocarcinoma.

Axillary lymphadenopathy is a local reaction to mRNA COVID-19 vaccination. A 19-year-old healthy woman presented with a mass in the axilla diagnosed by ultrasonography as vaccine-induced hyperreactive lymphadenopathy. After two weeks, ultrasonography revealed that the lymph node had shrunk and that the blood flow signal in the hilum had disappeared.

A 73-year-old man reported left low back pain worsening since 2 weeks. Ten days prior, he felt indefinable anxiety, which abated, but the back pain persisted. His diaphoretic and vasoconstrictive hands suggested hypovolemic shock. Emergency computed tomography revealed impending rupture of an abdominal aortic aneurysm. Emergent surgery saved his life.