Whole-body scans and immunohistochemistry of a patient with a complete response to therapy. A: Serial whole-body positron emission tomography/computed tomography scanning of a patient who developed a complete regression of metastatic melanoma. Scans show before and after treatment results. Mo, months. B: Immunohistochemistry of resected stable tumor mass after competing therapy. H&E, hematoxylin and eosin staining; HMB-45, melanoma marker antibody staining; CD68, macrophage lineage staining; CD56, natural killers staining; CD20, B-cell lineage staining; CD3, T-cell staining; CD4, staining for helper T cells; CD8, staining for cytotoxic T cells.