Syringocystadenoma papilliferum: light and electron microscopic studies.

Light microscopic and electron microscopic studies of a lesion displaying a typical histopathological picture of syringocystadenoma papilliferum (S.P.) are reported. Light microscopic serial sections showed that the tumor parenchyma extended to the epithelium just above the intrafollicular sebaceous duct. The tumor thus presumably develops from the epithelial region corresponding to the intrafollicular duct of the apocrine sweat gland. Electron microscopy revealed a non-keratinized intracytoplasmic cavity and intercellular canaliculi apparently formed as a continuation of this cavity. Keratinized cells were absent from the glandular and duct epithelium and even from the superficial epithelial portion of acanthotic areas. Neither myoepithelial cells nor secretory granules were identified in areas showing tubular, glandular, or sinusoidal structures. It was concluded that the tumor differentiates towards both the intrafollicular and intradermal duct of the embryonic apocrine sweat gland apparatus.