Scanning electron microscopy of the interior of cells in Hürthle cell tumors.

Four cases of Hürthle cell tumor were examined by scanning electron microscopy after being macerated to remove all soluble components. By all morphological criteria, Hürthle cells are oncocytes with their usual augmented complement of mitochondria. The Hürthle cell mitochondria either are ovate with central stacks of cristae or elliptical or rod-like with cristae that often are finger-like. As in salivary gland oncocytes, the shelf-like cristae are anchored to the inner boundary membrane by tubular necks. In some Hürthle cells, all of the mitochondria exhibit reticulate cristae. A few mitochondria harbor a globular inclusion in their inner compartment. The Golgi apparatuses are relatively simple, consisting of imbricated saccules that are edged by small, bud-like structures. The rare lumina in the midst of clusters of Hürthle cells are lined by numerous microvilli. Thus, scanning electron microscopy of macerated Hürthle cell tumors has revealed a number of features, especially of their mitochondria, that have escaped detection by transmission electron microscopy.