Muscle biopsy

Today I'm looking at a muscle biopsy from a 63-year-old female with muscle cramping and increased creatinine level. There appears to be a chronic inflammatory infiltrate surrounding scattered non-necrotic muscle fibers. This is most consistent with polymyositis. I suppose, given the prefix "poly", that by definition polymyositis is in more than one muscle. So, given that I have a single biopsy of a single muscle, I can only claim that these histologic findings are consistent with polymyositis.