The carcinoid tumor component was strongly and diffusely immunoreactive (3+, cytoplasmic staining) for CD56 (Figure 7A), chromogranin and synaptophysin (Figure 7B); weakly and focally immunoreactive (1+, cytoplasmic staining) for pancytokeratin (Figure 7C); and negative for CA-IX, CD99, CDX2, CK7, CK20 (Figure 7D) and SMA. The gene discussed is CD99; the disease is carcinoid tumor.