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Incidence of Pituitary adenomas

Histologic studies of pituitary glands obtained from unselected routine adult autopsies show the presence of incidental adenomas in 8 to 23 percent, suggesting that transformation in adenohypophyseal cells is a relatively common event, albeit one that is not always apparent clinically. The pituitary gland is a common substrate for neoplastic transformation, giving rise to approximately 15 percent of all diagnosed intracranial tumors.

 
 

The adenohypophysis is a functional endocrine unit composed of three anatomic parts: the pars distalis (anterior lobe), pars intermedia (intermediate lobe), and pars tuberalis (a sleeve of adenohypophyseal cells ensheathing the lower hypophyseal stalk). The pars distalis is the site of meticulously regulated hormone synthesis and release, and is also the principal site of clinically significant intrasellar pathology. Tumors arising from adenohypophyseal cells represent the most common form of primary neoplasia occurring in the sellar region. The overwhelming majority of these tumors are histologically benign adenomas, and although many exhibit varying degrees of local invasiveness, exceptionally few demonstrate the metastatic dissemination necessary for the designation pituitary carcinoma. Even so, the' 'benign" histology of pituitary adenomas is often an all too beguiling feature of their biology, for the regularity with which they encroach on critical neural structures, coupled with the distressing endocrinopathies they frequently induce, make them a frequent and significant source of patient morbidity and, occasionally, patient mortality.

The neurohypophysis, which includes the infundibulum, pituitary stalk, and posterior pituitary, rarely gives rise to clinically significant primary tumors. Granular cell tumors of the posterior lobe and pituitary stalk, though relatively common as incidental autopsy findings, rarely grow large enough to be of clinical significance. The remaining tumors of neurohypophyseal origin are gliomas, which are very rare. By contrast, the neurohypophysis is one of the favored intracranial recipient sites for metastatic disease. Metastatic deposits emanating from a variety of systemic malignancy are not uncommonly in the posterior lobe, and although most of these occur in the setting of advanced systemic disease, occasionally a posterior lobe deposit is the first manifestation of a unrecognized neoplastic process.

Pituitary adenomas have place in the common population in 25%, according to postmortum studies performed in several centers. Most of them are microadenomas and could be multiple. Most of the died were not complaining of them.
For some reasons, these microadenomas start to grow and regain variable hormonal activity. In the case that, they are active hormonally, they could be detected in the early stage.
When the pituitary adenoma hormonally inactive, then the clinical signs become evident when mass compression to the surrounding structures start to manifest the clinical presence of the pituitary adenomas.
Clinically diagnosed pituitary adenomas consist 15% of extra-axial intracranial tumors. The are usually benign in behavior, but when they become large, they regained morbidity with the expansion.
Clinical presentation discussed elsewhere, and the neuroradiologic and hormonal studies with the detailed evaluation of all the neural structures surrounding the mass is mandatory to have the proper decision of treatment.
In the past, the mortality rate was high in the surgical treatment of pituitary adenomas. Introduction of microscopic facilities and microsurgical techniques with improvement of the neurosurgical approaches not only lowered the mortality, but also the morbidity and negative drawbacks of the surgical intervention.
In 1985 I had a patent for the new surgical subfrontal approaches to the chiasmal region with mobilization and preservation of the olfactory tracts. These approaches are designed to the giant pituitary adenomas with massive suprasellar extension. The important point here is not the patent, but these modifications brought with them an entire package of surgical standards and concepts, that I realized that performing more than thousand operations in pituitary adenomas over 25 years, I never had mortality.
Thanks to the great neurosurgeon Prof. Tigliev G.S. who spent all the seconds of his life perfecting the neurosurgical standards in Leningrad. He died 2003, but he is living in our heart and all my experience is a continuum of the way of his thinking.


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