ECCRINE POROMA
Numerous epidermal connections by a uniform population of small keratinocytes having visible cytoplasmic borders are seen in eccrine poromas. The epithelium has the histochemical characteristics of the epithelium of the eccrine acrosyringium. The stroma is frequently quite vascular, and this is not location dependent. Although the foot and lower extremety are supposed to be the most common sites, over half of my cases have been from the head or neck. The architecture is frequently dome-shaped as in this case, but poromas may be polypoid or even verrrucoid. The small keratinocytes comprising these tumors may be indistinguishable from those found in some seborrheic keratoses. The marked acanthosis and lack of pseudohorn cysts are more characteristic of poromas. The same acrosyringeal cell population is seen in dermal duct tumors, and these differ from poromas by the lack of epidermal connections. There are cases where just a few epidermal connections are demonstrated, and the diagnostic choice is then arbitrary.

 
Eccrine poroma, scan power view. Note numerous epidermal connections by the tumor and the degree of acanthosis.
Low power view of above showing the vascular stroma and relatively uniform cell population.
High power view of the small kertinocyte population having distinct cytoplasmic borders.

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