I have a tumor on my right arm muscle. what could it be?

Anything from...: ... A benign lipoma to a vicious synovial sarcoma. If your physician is confident it's a benign lipoma, he/she may leave it alone. Otherwise, you'll be wise to allow excision for diagnosis (and who really wants a tumor on the arm?) a final diagnosis cannot be made until a pathologist has examined the excised tumor.

Have u seen an md?: If but just feeling a mass and have not had it looked it then that would be the first step. Torn or attained muscles can feel like a lump but usually with pain and difficulty with motion. If it is a tumor it most likely would be a fatty benign lipoma but these can become or b malignant. Physical exam and likely an MRI would be first steps to evaluate. Could b clot, lymph, met but need more info.