A case of adenoid cystic carcinoma which developed in the left parotid gland of an 11‐year‐old girl was studied by electron microscopy. Islands of tumor cells, showing glandular and cribriform appearances, infiltrated the surrounding tissue and nerves. True lumina and pseudocysts were present in the islands of tumor cells. Electron microscopic examination revealed two types of tumor cells; clear cells (secretory epithelial cells) and dark cells myoepithelium‐like cells). Some of the tumor cells, showing a transitional form between the two types, formed a part of the luminal wall. There were many crystalline spicules, cellular debris, and fine stellate granules in the lumina. Pseudocysts were composed of replicated basal laminae, fine stellate granules, and a central core of microfilaments. Rarely, a capillary was noted in the center of the pseudocysts. It is speculated that ultrastructural features of adenoid cystic carcinoma in children may differ from the adult cases in the following ways; they contain numerous crystalline spicules in the lumina, dark cells with microvilli forming the luminal wall, and fine capillaries in the pseudo
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