SERPINB5 and neoplasm: Taking SERPINB5 (encoding maspin) as a specific example, we reasoned that the rare expression of such genes in histologically normal differentiated cells and more commonly in preneoplastic lesions (Smith et al, 2003) and tumours might be a consequence of a failure to appropriately inactivate these sequences in differentiation-committed progeny during the asymmetric division of multi-potent cells (Heighway et al, 2004).