Thoracic cage is the site of development of various primary or metastatic tumors. An aneurysmal rib cyst is a benign tumor arising from the chest wall. Aneurysmal rib cyst is considered a rare surgical entity and its presence must be followed by removal for histology examination. We present here the case of an aneurysmal rib cyst to a young 33-year-old female. The tumor was presented as an expanding left anterior second rib mass during a self-breast examination. Chest x-ray showed a shadow on the left upper lung area and CT scan revealed a large multicystic mass in the anterolateral left 2nd rib protruding underneath the thoracic major muscle. We discuss the clinicopathological characteristics of this tumor and its surgical management along with a short literature review.