Additionally, the teratomatous cyst wall was strongly and diffusely immunoreactive (3+, cytoplasmic staining) for smooth muscle actin (SMA, Figure 6C); and weakly and focally immunoreactive (1+, cytoplasmic staining) for carbonic anhydrase IX (CA-IX), CD99, chromogranin and synaptophysin. The gene discussed is CD99; the disease is cyst.