You’re a R1 Emergency Medicine Resident working a 23:00 - 07:00 shift, your favorite! Your next patient presented with acute onset of shortness of breath without exertion, a swollen face, and what appears to be bulging veins on their chest. You astutely suspect SVC syndrome. Your attending gives you a fist bump, as this is what he was thinking. He then asks: which of the following is the most common etiology for SVC syndrome?