IBM trichrome with highlighted r

This is a Gomori trichrome stain of skeletal muscle. The patient has inclusion body myositis (IBM). Note that most of the muscle fibers look pretty normal. However, there are a couple of fibers (encircled by the thick red line) which contain numerous rimmed vacuoles. These rimmed vacuoles are the inclusion bodies. Because not every fiber has inclusions, it is possible that a biopsy might not contain any affected fibers.