Clinical and histological characteristics of poroid neoplasms: a study of 25 cases in Taiwan.

Background Eccrine poroma (EP) are relatively common benign eccrine neoplasms. Other poroid neoplasms (PNs), namely hidroacanthoma simplex (HS), dermal duct tumor (DDT), and poroid hidradenoma (PH), are seldom reported. Methods Among 18 653 biopsy specimens received from January 1988 to October 2003, we found 25 PNs (0.134%). We conducted retrospective analysis and obtained clinical and histopathological information. Results There were 16 EP, 3 HS, 4 PH, and 2 PH coexisting with either HS or EP. No DDT was found. More than half of PNs presented as red-color neoplasms, but none were diagnosed correctly on clinical grounds alone. The most common preoperative diagnoses were pyogenic granuloma or soft fibromas. Most EPs were located on hair-bearing regions of the limbs (37.5%) and trunk (25%), instead of soles (18.8%) and palms (6.3%). Three HS showed no cuticular cell, but had monomorphic poroid cells. Most EPs (10/16) were composed of both poroid and cuticular cells. All PH were composed of cuticular and poroid cells. Horn cysts were found in three cases (12%). Most PNs (16/25) contained clear cells. Conclusions PNs are sudoriferous tumors that may vary considerably in clinical expression. EP, about 64% (16/25) of PNs in our series, was the most common. PH incidence is probably underestimated in the literature. We found six PHs in 25 PNs. Histopathologically, it is not justified to exclude PN diagnosis by noticing horn cysts. It was uncommon for two or three subtypes of PN to occur in a single lesion. [ABSTRACT FROM AUTHOR]