Monday, July 11, 2016
What is the current status of "atypical pituitary adenoma"?
What is the current status of "atypical pituitary adenoma" as a distinct entity? Currently, that designation remains in flux. Originally defined in the 2004 WHO Classification of Tumors of Endocrine Organs as a pituitary adenoma with "excessive" p53 immunoreactivity and a MIB1 proliferation index greater than 3%, the entity known as "atypical pituitary adenoma" has over time fallen into some disfavor. Since the literature on this entity is still evolving, some neuropathologists (including me) prefer to sign out such cases as "pituitary adenoma with elevated MIB1 proliferative index" with a comment suggesting that closer-than-usual clinical follow-up might be warranted. Finessing the diagnosis in this way may help the patient avoid automatic administration of radiation therapy while lowering the decision threshold to administer radiation at first recurrence.As for p53, use of that immunohistochemical index is even more controversial with some neuropathologists (including me) eschewing its use entirely in the setting of pituitary adenoma.
Kleinschmidt-DeMasters BK, Lopes MB, Prayson RA. An algorithmic approach to sellar region masses. Arch Pathol Lab Med. 2015;139(3):356-372.