A case of eccrine poroma with multiple transepidermal elimination

The skin functions to eliminate foreign substances through the epidermis to the epidermal surface; this process is called transepidermal elimination (TEE). TEE has been observed in various skin tumors. We encountered a 64-year-old male patient with eccrine poroma with marked TEE. A dark brown nodular papule appeared on the anterior aspect of his right leg about 20 years ago and gradually expanded. Histopathologically, cell nests of poroma were extruded to the epidermal surface at several sites. No erosion was noted, and mild to moderate inflammatory cell infiltration was observed in the upper layer of the dermis. According to Mehregan's classification, the TEE, phenomenon observed in our case may correspond to types 2 and 3.