Twelve cases of oral leukoplakia were studied at the light and electron microscopic levels. In clinical leukoplakia simplex and verrucosa, both light and electron microscopic investigations revealed evidence of increased keratinization. Clinically erosive and histologically dysplastic leukoplakias showed ultrastructural alterations characteristic of oral carcinomas in some instances.

Heterotopic tissue, identified by both light and electron microscopy as cardiac muscle, was detected at autopsy on the surface of the right superior temporal gyrus of a 73-year old female patient. The cells of the heterotopic tissue were interconnected by intercalated discs and the fibres contained regularly cross-striated, contracted, or relaxed myofibrils indicating a continuing contractile activity until the time of death.

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