Sarcoma under shoulder muscle?

SheTre

My brother was recently diagnosed with Sarcoma. He lives in another state so we don't talk much and see each other rarely. He hasn't told me what type of sarcoma it is. All I know is that he had a tennis ball sized tumor under a muscle around his shoulder area. He went to the doctor because of extreme chronic pain in his shoulder. The doctor knew there was a problem when he was able to visually see the tumor when my brother took his shirt off. They had to go in and lift up the muscle in order to get a sample for biospy. It's undifferentiated and its sarcoma. That's all I know. He is scheduled for chemo and radiation therapy to shrink the tumor before they attempt surgery. What type of sarcoma does this sound like?