Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 57 4 2019 07 13 276 279 EN Soleyman Heydari Trauma Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. AND Department of Surgery, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran. Mohammad Javad Behzadnia Trauma Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. AND Department of Emergency Medicine, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran. Fatemeh Saboori Cancer Institute, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. 2018 05 02 2018 12 19 Male breast enlargement as gynecomastia may be as a sign of underlying systemic diseases. Male breast malignancy is also considered in differential diagnosis. We present a young man with primary chest wall lymphoma as gynecomastia, without pre-existing problem or other disease. Here, we present his clinical manifestation, management, and his early outcome. Chest wall lymphoma as an initial presentation of isolated chest wall mass in males is a rare clinical entity and its presentation as gynecomastia is even extremely unusual. https://acta.tums.ac.ir/index.php/acta/article/view/7240 https://acta.tums.ac.ir/index.php/acta/article/download/7240/5251