Immunohistochemical analysis aids in distinguishing SEDC from SCC and other adnexal tumors, with SEDC typically expressing epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) in ductal regions, a staining pattern absent in SCC [4,14]. The gene discussed is CEACAM5; the disease is spondyloepiphyseal dysplasia congenita.