Immunohistochemistry usually shows a characteristic staining profile of ECD cells (positive CD68, CD163, and factor XIIIa and negative CD1a and CD207), whereas S-100 positivity is rare.[18] Immunohistochemical analysis of BRAFV600E staining detected mutant protein in histiocytic neoplasms in more than 50% of ECD patients. The gene discussed is CD68; the disease is familial atrioventricular septal defect.