Eight cases of malignant eccrine poromas were studied immunohistochemically with a broad panel of antibodies in order to better characterise the spectrum of their differentiating pathways. Special attention was paid to the expression of cytokeratins, mainly the newly recognised keratin 20. In general, the pattern of staining agreed to previous studies. Anyway, a non-expected positivity with keratin 20 was seen in two cases. The usefulness of the immunohistochemistry to discover areas with masked differentiation in adnexal tumours of the skin was once more confirmed.