PTPRC and small cell lung carcinoma: They expressed high levels of cytokeratins (PanCK), markers of epithelial tumors, calcitonin gene–related peptide (CGRP), and synaptophysin (Syp), markers for SCLC of neuroendocrine origin (Meuwissen et al., 2003), but were negative for CD45, a marker for cells of hematopoietic origin (Fig. 9 C).