Acral syringoma: electron microscopic studies on its origin.

A case of acral syringoma associated with the usual eruption on the lower eyelids was examined by light and electron microscopy for the first time. In the upper dermis there were a few ducts and cystic formation, while predominant atypical solid strands composed of tumor cells were often seen by light microscopy. Electron microscopy showed the formation of small ducts in the solid strands and numerous microvilli with a pinching off of the luminal tumor cells. A large number of multivesicular dense bodies (mvb) and keratohyalin granules were also found in the periluminal tumor cells. The ducts resembled embryonic intra-epidermal ducts. The unusual anatomical sites of eruption and the electron microscopic findings suggest an eccrine intra-epidermal duct origin of acral syringoma.