OTP and small cell lung carcinoma: Other markers used to characterize SCLC are: B-cell lymphoma 2 (BCL2; expressed often), P16 nuclear staining (expressed in 95–100% of cases), tyrosine-protein kinase KIT (CD117/c-KIT; expressed in about 60% of cases, retinoblastoma protein (P-RB; always negative), and homeobox protein orthopedia (OTP, always negative) [29].