Introduction. Malignant eccrine poroma, also called eccrine porocarcinoma, is a rare tumour of the dermal adnexa, derived from the acrosyringial duct of sweat glands. Historically it has been classified among a heterogenous group of adnexal skin tumours. It most probably originates from a pre-existing benign lesion (eccrine poroma) as against othermalignant tumours of the sweat glands which appear malignant from the start. Material and methods. The authors diagnosed a malignant skin lesion on the forehead 12x 12 cm in the fronto-temporal region. Within a period of two years it was the third surgical intervention, each time at a different facility. Preceding histology gave evidence of a spinocellular carcinoma. The lesion underwent radiotherapy, however, it recurred and grewlarger.Biopsymaterial was examined with the aid of classical staining methods and a wide array of immunohistochemical methods. Consequently, plastic surgery was performed - transplantation of skin from the patient’s thigh to the excised part of her face and head. Results. The tumour was made up of solid nests of atypical cells that in places contained abrupt keratinization, elsewhere in the form of narrow ducts in places with two layers of epithelium. The tumour parenchyma was buried in a denser, even hyalinized tumour stroma and infiltrated the epidermis as well as the dermis. Immunohistochemically the cells displayed CEA, EMA, Ck 18, 19, singularly containing a PAS-positive substance. Sialomucins were absent. On the basis of the results presented, the authors diagnosed a malignant tumour stemming from the acrosyringium, most probably an eccrine poroma. Conclusion. A rare malignant tumour of the skin has been described and discussed were the subtyping of tumours of the dermal adnexa, the histomorphology and immunohistology of the sweat glands, as well as the differential diagnostics of malignant eccrine poroma.

        Key words: malignant eccrine poroma - immunohistochemical examination - CEA, EMA, Ck 18, 19 - differential diagnosis