Oncocytic Adrenocortical Tumors

Oncocytic tumors of the adrenal cortex are very uncommon. Arriving at the correct diagnosis is important and the use of mES-13 immunohistochemical testing or ultrastructural analysis can support their recognition. However, once the diagnosis is established, trying to predict their biologic behavior is even more important. The Weiss system, considered to be predictive of the biologic behavior of conventional (nononcocytic) adrenocortical tumors, has been recently reviewed in the context of its possible application to the oncocytic tumor variant, along with the introduction of the size and weight parameter. Definitional criteria (mainly cells with eosinophilic and granular cytoplasm, high nuclear grade, diffuse architectural pattern) common to all types of oncocytic tumors are outlined, and proposed major criteria (high mitotic rate, atypical mitoses, venous invasion) and minor criteria (large size and huge weight, necrosis, capsular invasion, sinusoidal invasion) for distinguishing malignant tumors are discussed. As a starting point for this discussion, a case of uncertain malignant potential is presented. The authors’ proposed working rules for diagnostic categorization of such tumors are defined, with the presence of 1 major criterion indicating malignancy, 1 to 4 minor criteria indicating uncertain malignant potential (borderline), and the absence of all major and minor criteria indicative of benignancy.