What characterizes oncocytomas?

Oncocytomas are characterized by large eosinophilic cells that are notable for the presence of large nucleoli. These cells contain an abundance of mitochondria, leading to their characteristic eosinophilic (or pink-staining) appearance when viewed under a microscope. The presence of large nucleoli is significant as these structures often indicate a high level of metabolic activity, which is consistent with the features of oncocytomas.

The eosinophilic cytoplasm and prominent nucleoli are key histological features that help in distinguishing oncocytomas from other types of tumors. Their cellular composition is reflective of the tumor's origin, typically arising from epithelial cells in organs like the kidney and salivary glands. Therefore, the diagnosis of oncocytoma relies heavily on these histological characteristics, confirming the answer choice that includes large eosinophilic cells with large nucleoli.