Nowadays, surgery, radiotherapy and chemotherapy are the most frequently used modalities in the treatment of breast cancer. It is very well-known that some severe complications may result from after these treatments. Early and late complications of radiotherapy are well known. The complications of radiation therapy may be seen in (early) or after three months (late-delayed) of periods. These complications may be related with direct or indirect effect of radiation. The radiation fibrosis syndrome is a progressive fibrotic tissue sclerosis together with various clinical symptoms in the irradiation field. It is usually a late finding of radiation therapy and may be seen weeks or even years after the treatment. Many systems such as musculo-skeletal, soft tissue, neural tissue and cardiopulmonary system may be affected. In this report, we present a case of a breast cancer treated with breast conserving surgery and radiation therapy twelve years ago. The patient had ipsilateral lymphedema, right axillary mass, and pain during arm and shoulder mobilization. Her physical examination and radiologic findings revealed a big mass invading right thoracic wall, thoracic cavity and the axilla. Histopathological evaluation performed after tru-cut and open biopsy from the mass showed fibrosis resulting from radiation therapy.