The case was 70 years old, female. She visited a nearby hospital complaining of a mass in the right breast which was diagnosed as a chest wall tumor and referred to our department. A computed tomography (CT) scan revealed a 10 cm-sized contrast enhanced mass with bone destruction of the 3rd and 4th ribs. Invasion to the mammary gland tissue was not observed. A malignant tumor was suspected by percutaneous needle biopsy and the tumor was excised with the chest wall including the 3rd, 4th and 5th ribs. Histopathological diagnosis was a pleomorphic rhabdomyosarcoma. No signs of recurrence have been observed for 5 years after the operation.