Lesions having this type of pathology have also been described as malignant eccrine poroma, malignant hidroacanthoma simplex, and eccrine porocarcinoma, with the qualification that the lesion is not invasive. The term 'intraepithelial epithelioma of Jadassohn and Borst' is better avoided for a variety of reasons too lengthy to present at this time. The presence of clusters of cytologically atypical epithelial cells that are morphologically distinct from their neighbors and separated from the dermoepidermal junction by several layers of normal keratinocytes is characteristic of this lesion. Occasionally, and not specifically, a peculiar form of parakeratosis that has been designated as ' necrosis en masse' in benign acrosyringeal tumors is seen over clusters of such cells that have reached the surface of the epidermis.
Verrucous architecture is sometimes present, but the architecture is variable from case to case.
A CEA should be done in doubtful cases. The basal layer is rarely spared by the atypical melanocytes. A CEA and an S-100 would solve the problem. The location of the lesion is helpful. Epithelial mucin is present in most of these cases, and this mucin is usually positive by the PAS method after diastase or is aldehyde fuchsin positive.