Tjarks BJ, et al. - An inquiry was set up with regard to the diagnostic utility of the nuclear immunohistochemical stains for sebaceous neoplasms by comparing their staining pattern to adipophilin, a consistently positive cytoplasmic stain. The findings revealed Factor XIIIa (AC-1A1) as a sensitive and specific nuclear marker for sebaceous differentiation. Its diagnostic utility exceeded that of adipophilin. Hence, the inclusion of Factor XIIIa was recommended in the expanding group of immunohistochemical and special stains which could be utilized to assist in the diagnosis of sebaceous neoplasms.