Aneurysmal bone cyst (ABC) is a benign, locally aggressive tumor of long bone and vertebral bodies. Soft tissue aneurysmal bone cyst (STABC) is an extremely rare entity that has same morphology as their osseous counterparts. The aim of this study is to keep in mind STABC in differential diagnosis of some benign and malignant tumors. A 68-year-old male presented with a swelling on his right shoulder. Radiographic imaging revealed a 9 cm calcified mass in latissimus dorsi. Excision material was interpreted as STABC. STABC is a tumor which is composed of cystic areas intermingled with reactive bone formation, hemorrhage, mononuclear cells, spindle cells and osteoclastic giant cells. This tumor has morphological features in common with variable benign and malignant entities so that it must be kept in mind for differential diagnosis.