Chest Film Clinic: What caused a solitary pulmonary mass in this patient with fever?

A 45-year-old man presented to the emergency department (ED) with fever and left-sided pleuritic chest pain. He had been in good health until 4 days earlier, when diffuse myalgias, weakness, and frontal headache developed. Two days later, these symptoms were accompanied by onset of fever (temperature, 39.4°C [103°F]) and left-sided pleuritic chest pain. He denied chills, rigors, shortness of breath, hemoptysis, and cough.