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.


jkunicki said...

Due to the lack of standards and a validated cut-off for p53 as well as some concerns with Ki67 cut off value for atypical pituitary adenomas there is still some confusion. Another problem with atypical adenomas is widely criticized lack of definition of invasiveness and incorporation of this parameter in 2004 WHO classification. The clinico-pathological studies show a wide range ( 2.7% - 15%) of atypical adenomas, according to different interpretations of its definition.
In Europe there is a growing interest in novel clinicopathological classification proposed by Jacqueline Truillas group.The classification takes into account tumour invasion and proliferation and seems to have honest clinical validation. It’s a new look at an quite known theme.

A new prognostic clinicopathological classification of pituitary adenomas: a multicentric case-control study of 410 patients with 8 years post-operative follow-up.
Trouillas J, Roy P, Sturm N, Dantony E,et al. Acta Neuropathol. 2013 Jul;126(1):123-35. doi: 10.1007/s00401-013-1084-y. Epub 2013 Feb 12.

Julie Mc. said...

My son had a macroprolactinoma initially misdiagnosed as non functioning so tumor was partially resected and pathology performed. I do not have access to read the WHO 2017 pituitary guidelines but I do understand they have dropped "atypical" and provided new standards for considering a tumor aggressive. My son's pathology showed Ki67 of 3.98% with mitosis less than 1 per 10 HPF. No p53 testing was done. His tumor was invasive, encasing his left carotid artery. Based upon what you may know of the WHO 2017 changes, what do you think of these results?