Small cell undifferentiated carcinoma of salivary gland origin: an ultrastructural study.

A case of small cell carcinoma of salivary gland was studied by light and electron microscopy. Light microscopy showed sheets of small uniform cells with scanty cytoplasm and pyknotic nuclei. Electron microscopy showed two distinct cell types; an electron-lucent epithelial-appearing cell, and a denser cell with processes containing bundles of filaments and other features suggesting myoepithelial differentiation. Neurosecretory granules were absent. These findings support a salivary duct origin, and are evidence against a neurendocrine derivation for this tumor.