Abstract
INTRODUCTION: Pirfenidone was approved in 2014 for the treatment of idiopathic pulmonary fibrosis. Pirfenidone inhibits several factors such as tissue growth factor-β and platelet-derived growth factor, leading to decreased epithelial and fibroblast proliferation and collagen synthesis. The drug improves progression-free survival and is well tolerated, with minimal side effects. However, data on its long-term effects are lacking. CASE PRESENTATION: We present a rare case in which an undifferentiated pleomorphic sarcoma developed in a 59-year-old man with idiopathic pulmonary fibrosis who was treated with pirfenidone for more than a year. DISCUSSION: Undifferentiated pleomorphic sarcoma, also known as malignant fibrous histiocytoma, is a soft-tissue sarcoma arising from fibroblasts. The disease presents in the extremities and the trunk of elderly patients, and rarely in the retroperitoneum. Surgical excision is the mainstay of treatment; however, recurrence is common in the form of lung and lymph node metastases. In this report we review this rare malignancy and highlight the need for postmarketing longitudinal studies to determine additional adverse effects in patients with idiopathic pulmonary fibrosis who are on pirfenidone therapy.