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Free keywords:
Pituitary, adenoma, Classification, WHO, clinical impact
Abstract:
WHO classifications should be used for comparing the results from
different groups of pathologist and clinicians by standardized
histopathological methods. Our present report describes the important
parameters of pituitary adenoma pathology as demand of the WHO
classification for correlation to endocrine data and prognosis. The
combination of HE stain based structures with immunostainings for
pituitary hormones allows subclassification of adenomas as the best
method not only for correlations to clinical hyperfunctions but also for
statements to the sensitivity of drug therapies (somatostatin analogs,
dopamine agonists). GH-, PRL- and ACTH-secreting pituitary adenomas are
further classified based on the size and number of their secretory
granules by electron microscopy, or as is mostly the case nowadays by
cytokeratin staining pattern, into densely and sparsely granulated.
Granulation pattern may be considered for the prediction of treatment
response in patients with GH-secreting adenomas, since the sparsely
granulated subtype was shown to be less responsive to somatostatin
analog treatment. For prognosis, it is important to identify aggressive
adenomas by measurements of the Ki-67 index, of the number of mitoses,
and of nuclear expression of p53. Among the criteria for atypical
adenomas, high Ki-67 labeling index and invasive character are the most
important adverse prognostic factors. Promising molecular markers have
been identified that might supplement the currently used proliferation
parameters. For defining atypical adenomas in a future histopathological
classification system, we propose to provide the proliferative potential
and the invasive character separately.
