Calreticulin expression is variable in the plasma cells of patients with systemic AL-amyloidosis by immunohistochemical staining of bone marrow biopsies. In these images from adjacent sections of bone marrow biopsies from 2 patients, CD138⁺ plasma cells stained immunohistochemically are shown on the left and calreticulin on the right. A pathologist who did not know the clinical status of the patients scored all cases blindly for intensity and distribution of calreticulin to compute the calreticulin index. In panel A, the calreticulin index of 9 is a function of the intensity of staining, indicating that calreticulin was found in a pancytoplasmic distribution. In panel B, the calreticulin index of 3 is a function of an intensity score of 1, indicating that the distribution of calreticulin was rare and scattered.