Abstract
A 74-year-old man first noticed a tumor on his right hand 5 years previously. On physical examination, a red, hemispherical tumor measuring about 13×9 mm in size was found on the back of his right hand. A histopathological examination showed a large cyst in the dermis. Within the cyst wall, small solid components consisting of poroid cells were observed. The tumor was diagnosed to be poroid hidradenoma, which was a new variant of poroma first described by Abenoza and Ackerman in 1990. An immunohistochemical examination using monoclonal antikeratin antibodies revealed the poroid cells to differentiate toward the eccrine dermal ducts, whereas the luminal cells differentiated toward the dermal ducts to the secretory regions.
