Immunostaining showed the axillary tumor to be positive for cluster of differentiation (CD) antigen 34, CD31 (Fig. 5e, f) and erythroblast transformation specific-related gene, while negative for cytokeratin AE1/3, epithelial membrane antigen, and thyroid transcription factor-1 (data not shown). The gene discussed is PECAM1; the disease is neoplasm.