LAUSR

BACKGROUND Few studies have addressed the efficacy of pembrolizumab in pulmonary sarcomatoid carcinoma (PSC), a rare, previously rapidly fatal subtype of non-small-cell lung cancer. CASE SUMMARY We report the case of a 69-year-old man presented with respiratory distress caused by a large left upper lung lobe mass diagnosed as PSC with programmed death-ligand 1 expressed on more than 50 percent of tumor cells. The patient was started on pembrolizumab and, after 5 cycles, there was a more than 80 percent decrease in the size of the tumor mass. Further decrease was seen at the end of 10 cycles. The patient has been tolerating pembrolizumab well, with no limiting side-effects. Fourteen months after first coming into the hospital, he remains asymptomatic. CONCLUSION Pembrolizumab appears as a viable emerging treatment for PSC.