Because the properties of EWS-Oct-4B are very similar to those of EWS-Oct-4, it would be interesting to investigate whether abnormal expression of EWS-Oct-4B in two types of epithelial tumours, hidradenoma of the skin and mucoepidermoid carcinoma of salivary glands, also contributes to the induction of the incomplete embryonic transition. This evidence concerns the gene POU5F1 and salivary gland mucoepidermoid carcinoma.