The correlation of Ki-67 staining indices with tumour doubling times in regrowing non-functioning pituitary adenomas

Ki67 in endocrine neoplasms: to count or not to count, this is the question! A systematic review from the English language literature

BACKGROUND

Endocrine neoplasms are generally slow-growing tumors that can show hormonal activity and give metastases. In most cases they are benign and clearly malignant forms are easy to diagnose. However, borderline forms may occur and be, for the pathologists, very difficult to classify. In these cases, there is a strong need to identify factors that may aid. Official classification systems for endocrine neoplasms are based on the evaluation of proliferation and, in most cases, they rely on mitotic count. In support, the study of Ki67 is carried out which, however, has not yet been included in any official classification system, except for neuroendocrine neoplasms of the gastro-entero-pancreatic tract.

PURPOSE

The aim of the present study was to investigate the proven or unproven role of Ki67 in endocrine neoplasms, in different districts, in order to bring to light the substantial differences, in terms of proliferation, existing between neoplasms so similar, but at the same time, so different.

METHODS

A thorough search of English language literature was performed, looking for articles concerning Ki67 in five endocrine neoplasms (pituitary adenomas, thyroid neoplasms, adrenocortical neoplasms, pheochromocytomas and paragangliomas).

RESULTS

From 2170, 236 articles were selected and it was seen that the endocrine neoplasm in which Ki67 was most studied was the pituitary, where it still shows a controversial role. In other neoplasms different roles were identified.

CONCLUSION

The pathologist should be aware of the contribution that this proliferative marker can give to the diagnosis and, sometimes, to the therapy selection, for the clinician.

Adrenocorticotropic Hormone Secreting Pituitary Adenomas: Analysis of Growth Fraction Using the MIB-1 Antibody

AIMS AND BACKGROUND

Pituitary adenomas are usually considered well differentiated tumors, even if in about one third of cases they invade surrounding tissues, with the possibility of postoperative relapse after complete surgical removal. Adrenocorticotropic hormone (ACTH) secreting adenomas seem to be the most infiltrating subtype, with a higher incidence of recurrence. Ki-67 is a nuclear antigen which is easily detectable by means of the MIB-1 monoclonal antibody, and the labeling index (LI) obtained can be considered a marker of tumor proliferation.

METHODS

In order to identify the growth fraction of these tumors we used the MIB-1 antibody to evaluate the expression of Ki-67 antibody in 11 ACTH secreting pituitary adenomas and to compare it with the LI obtained in 98 other hormone secreting or non-functioning pituitary adenomas consecutively operated on during a 40-month period.

RESULTS

In relation to surgically verified infiltration of the sellar floor dura and bone, we identified eight non-invasive and three invasive ACTH secreting pituitary adenomas. All invasive tumors infiltrated the wall of the cavernous sinus (CS). The mean Ki-67 LI was 5.88 +/- 9.13% versus 2.33 +/- 2.40% in non-ACTH secreting adenomas (P = 0.0025). It was 13.27 +/- 15.42% in invasive and 3.11 +/- 4.37% in non-invasive ACTH adenomas, and 18.40 +/- 17.82% in patients over 50 years versus 3.10 +/- 4.09% in younger subjects (P = 0.02).

CONCLUSIONS

Ki-67 LI is a useful marker in the determination of proliferative activity and invasiveness of anterior pituitary adenomas. Our data seem to confirm that ACTH secreting adenomas have a higher growth fraction than other pituitary adenomas and this observation presumably explains the higher incidence of relapse of these tumors even after macroscopically total removal.

Non-functioning pituitary adenoma underwent surgery: A multicenter retrospective study over the last four decades (1977-2015)

OBJECTIVE

To assess clinical features, diagnostic procedures, therapies and outcomes in patients with clinically non-functioning pituitary adenomas (NFPAs) surgically treated over the last four decades.

DESIGN AND METHODS

A multicenter retrospective study in NFPA patients periodically followed up in specialized neuroendocrinology units who underwent surgery in the period 1977-2015 was performed.

RESULTS

A total of 131 patients were studied [66 women (50.4%); mean age 52.6±14.8years (range, 15-82)]. Median diameter of the adenoma was 2.6cm (interquartile range, 2.0-3.1). The most frequently type of surgery used was endoscopic endonasal surgery (58.5%) followed by microscopic transsphenoidal surgery (37.4%). Radiation therapy was used in 19 patients (14.5%). Ki-67 labeling index performed in 54 patients was ≤2% in 70% samples. After a median follow-up time of 57months (25 to 128months), tumor diameter significantly decreased to 0.9cm (0-1.8cm), p<0.001. Multivariant analysis showed that endoscopic endonasal surgery (HR 2.74, 1.06-6.87, p=0.036) and radiotherapy (HR 0.04, 0.02-0.65, p=0.024) behaved as positive and negative predictors, respectively, of tumor absence in the follow-up. Endoscopic endonasal surgery (HR 6.71, 1.45-31.05, p=0.015) was the only positive predictor for complete cure in the follow-up.

CONCLUSION

NFPAs surgically treated in Spain are usually macroadenomas diagnosed around the sixth decade of life with no sex predilection. Type of surgery is associated with clinical outcome. Endoscopic endonasal surgery behaves as a positive predictor for the absence of tumor imaging and complete cure in the follow up.

Clinical Impact of the Current WHO Classification of Pituitary Adenomas

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.

Update on prognostic factors in acromegaly: Is a risk score possible?

Certain clinical conditions and markers have recently been demonstrated to modify the natural history of acromegaly in affected patients. Thus, some clinical, histological, radiological and molecular factors are associated with more aggressive pituitary tumors that have higher biochemical activity, higher tumor volumes and decreased tumoral and biochemical responses to current therapies. However, these factors do not seem to have an equal influence on the prognosis of patients with acromegaly. We present a review of the factors that influence the clinical course of patients with acromegaly and propose a risk value for each factor that will allow prognostic scoring for affected patients by considering a combination of these factors.

Null cell adenomas of the pituitary gland: an institutional review of their clinical imaging and behavioral characteristics

The aim of the study was to establish if the null cell adenoma (NCA) forms a distinct subgroup with unique clinicopathological characteristics within the nonfunctioning pituitary adenoma group particularly in relation to the silent gonadotroph adenomas (SGAs). We identified 31 patients with the pathological diagnosis of NCA verified by routine histology and immunohistochemistry with distinct differentiation from SGAs by an established negative testing for SF-1 at the Toronto Western Hospital between December 2004 and August 2010. We reviewed their demographic data, clinical features, magnetic resonance imaging, and the histologic variables: MIB-1, FGFR4, and P27. We compared these to 63 SGAs identified within the same period. All the NCAs were macroadenomas with diameter ranging from 15-57 mm and tumor volumes between 1.95-53.5 mm(3). Preoperative cavernous sinus tumor growth was able to predict the presence of a residual after surgery (p = 0.023). Furthermore, preoperative cavernous sinus extension (p = 0.002) and negative P27 expression (p = 0.035) were able to independently predict the subsequent growth of the postoperative tumor residual. Comparing the NCA to SGA, we found that MIB-1 was higher in NCA (mean ± SD = 3.43 ± 2.76 %) compared to SGAs (mean ± SD = 2.49 ± 1.41 %) (p = 0.044). The preoperative and postoperative tumor volume doubling times (TVDTs) displayed a negative correlation in the SGA (r = -0.855, p = 0.002) while in the NCA, a positive correlation was evident (r = 0.718, p = 0.029). Our study suggests that the NCAs are a distinct group with differing behavioral characteristics from the SGAs. It also appears that the finding of cavernous sinus extension on preoperative imaging and a negative P27 expression on immunohistochemistry in NCAs may be valuable tools in predicting residual tumor growth which may impact on postoperative care.

Combined high-field intraoperative magnetic resonance imaging and endoscopy increase extent of resection and progression-free survival for pituitary adenomas

PURPOSE

The clinical benefit of combined intraoperative magnetic resonance imaging (iMRI) and endoscopy for transsphenoidal pituitary adenoma resection has not been completely characterized. This study assessed the impact of microscopy, endoscopy, and/or iMRI on progression-free survival, extent of resection status (gross-, near-, and sub-total resection), and operative complications.

METHODS

Retrospective analyses were performed on 446 transsphenoidal pituitary adenoma surgeries at a single institution between 1998 and 2012. Multivariate analyses were used to control for baseline characteristics, differences during extent of resection status, and progression-free survival analysis.

RESULTS

Additional surgery was performed after iMRI in 56/156 cases (35.9%), which led to increased extent of resection status in 15/156 cases (9.6%). Multivariate ordinal logistic regression revealed no increase in extent of resection status following iMRI or endoscopy alone; however, combining these modalities increased extent of resection status (odds ratio 2.05, 95% CI 1.21-3.46) compared to conventional transsphenoidal microsurgery. Multivariate Cox regression revealed that reduced extent of resection status shortened progression-free survival for near- versus gross-total resection [hazard ratio (HR) 2.87, 95% CI 1.24-6.65] and sub- versus near-total resection (HR 2.10; 95% CI 1.00-4.40). Complication comparisons between microscopy, endoscopy, and iMRI revealed increased perioperative deaths for endoscopy versus microscopy (4/209 and 0/237, respectively), but this difference was non-significant considering multiple post hoc comparisons (Fisher exact, p = 0.24).

CONCLUSIONS

Combined use of endoscopy and iMRI increased pituitary adenoma extent of resection status compared to conventional transsphenoidal microsurgery, and increased extent of resection status was associated with longer progression-free survival. Treatment modality combination did not significantly impact complication rate.

Radically resected pituitary adenomas: prognostic role of Ki 67 labeling index in a monocentric retrospective series and literature review

Ki-67 Labeling Index is an immunocytochemical marker of cell proliferation. The correlation of Ki-67 expression with pituitary adenomas recurrence has been investigated and is highly debated. Aim of this study was to evaluate whether Ki-67 correlates with recurrence even in patients with an apparently completely removed pituitary adenoma. We retrospectively reviewed the database of the Hypothalamic-Pituitary Disease Unit at the Catholic University of Rome, collected between 2003 and 2011. Inclusion criteria were: patients who underwent surgery at the Department of Neurosurgery with an apparently complete removal of a pituitary adenoma; Ki-67 histological evaluation by the same operator and values of <3%. All patients underwent endocrine evaluation of the hypothalamic-pituitary function, ophthalmologic and neuro-radiological examinations, during the preoperative period and follow-up. Out of 490 patients recorded on the database of the Hypothalamic-Pituitary Disease Unit at the Catholic University of Rome, 191 cases met the inclusion criteria. Recurrence was observed in 49 cases (25.7% of the patients who had undergone radical excision). Optional cut-off value was identified at Ki-67 values of 1.50%. This was associated with worse disease-free survival time, even after correction for age at treatment, gender, positivity to p53, functional classification and Knosp grading. Ki-67 labeling index may be useful in postoperative management, even in patients who underwent radical PA removal. We suggest a Ki-67 cut-off value of 1.5% to plan an adequate clinical follow-up.

Growth patterns of pituitary adenomas and histopathological correlates

CONTEXT

The factors associated with pituitary adenoma (PA) growth rate remain unclear.

OBJECTIVE

The objective of the study was to establish whether the preoperative growth and extension pattern of PA can predict postoperative growth rate and recurrence in addition to whether the PA growth rate correlates with proliferation and growth factor expression.

PATIENTS

One hundred fifty-three consecutive patients who underwent surgery for pituitary adenoma from 1999 to 2011 at Toronto Western Hospital were identified.

MAIN OUTCOME MEASURES

The PA growth rate was measured both pre- and postoperatively, and its association with patient demographics, magnetic resonance imaging, and histolopathological parameters was determined.

RESULTS

The preoperative growth rate was associated with age (P = .0001), suprasellar growth (P = .003), the presence of a cyst/hemorrhage (P = .004), the mindbomb homolog-1 (P = .005), fibroblast growth factor receptor-4 positivity (P = .047), and p27 negativity (P = .007). After surgery, there were 34.6% residual volumes, which were associated with older age (P = .038) and also with growth patterns including anterior, posterior, suprasellar, and cavernous sinus extension (P = .001); 43.3% of these residuals grew and postoperative growth rate was calculated. Pre- and postoperative growth rates were correlated (r = 0.497, P = .026). Postoperative growth rate was associated with age (P = .015) and gender (P = .017).

CONCLUSIONS

Our data suggest that the growth rate of PAs are influenced by various patient- and tumor-specific characteristics including the age and sex of the patient, the specific subtype of PA, its hormonal activity, its immunohistochemical profile including the mindbomb homolog 1 labeling index status, and its preponderance for different growth directions relative to the pituitary fossa. Furthermore, the pre- and postoperative PA growth rates were correlated, suggesting that postoperative PA growth rates can be predicted, in part, by preoperative growth rates, thus better informing postoperative outcome.

Nonfunctioning pituitary adenomas: association of Ki-67 and HMGA-1 labeling indices with residual tumor growth

BACKGROUND

The postoperative biological behavior of nonfunctioning pituitary adenomas (NFPAs) is variable. Some residual NFPAs are stable long-term, others grow, and some recur despite complete removal. The usual histological markers of tumor aggressiveness are often similar between recurring, regrowing, and stable tumors, and therefore are not reliable as prognostic parameters. In this study, the clinical utility of proliferation indices (labeling index, Li) based on immunohistochemistry targeted at antigens Ki-67 and High-mobility group A1 (HMGA-1) for prediction of NFPA prognosis was investigated.

METHODS

Fifty patients with NFPAs were investigated. In each patient, Ki-67 and HMGA-1 Li were evaluated. Based on postoperative magnetic resonance images, patients were classified as tumor-free (18 patients), or harboring a residual tumor (32 patients). The latter group was further subdivided into groups with stable tumor remnants (11 patients) or progressive tumor remnants (21 patients).

RESULTS

The median follow-up period was 8 years. No significant relationship between HMGA-1 Li and residual tumor growth was found. Growing residual tumors showed a trend towards higher Ki-67 Li compared with stable ones (p = 0.104). All tumor remnants with Ki-67 Li above 2.2% were growing. The relationship between residual tumor growth and Ki-67 Li exceeding the cutoff value of 2.2% was significant (p = 0.01 in univariate, p = 0.044 in multivariate analysis).

CONCLUSIONS

The prognostic significance of the HMGA-1 antigen was not confirmed. In contrast, the Ki-67 Li provides useful and valuable information for the postoperative management of NFPAs. In residual adenomas with a Ki-67 Li above 2.2%, regrowth should be expected, and these tumors may require shorter intervals of follow-up magnetic resonance imaging (MRI) and/or early adjuvant therapy. Future larger studies are needed to confirm the results of this study.

Towards an integrated molecular and clinical strategy to predict early recurrence in surgically resected non-functional pituitary adenomas

Pituitary adenomas (PA) are histologically benign tumors of the sella that are capable of recurrence following resection. No mechanism exists to predict accurately the risk of recurrence in patients with PA following successful gross total surgical resection. We used microarray-based gene expression profiling to search for genotypically distinct subgroups of non-functional PA associated with the early recurrent phenotype. Rigorous phenotypic controls were used to select four patients with PA with early (<12 months) recurrence and seven patients with non-recurrent PA for comparative molecular analysis. Seventy genes with differential expression patterns between the phenotypic groups were identified, although this required some relaxation of rigid multiple-testing corrections. While some of these genes may therefore represent statistical false discoveries attributable to limited sample size, the CHL1 gene has a differential expression patterns that suggests a potential role as a predictor of recurrence phenotype. Transcriptome-level differences between early recurrent and non-recurrent non-functional PA appear to be subtle, although CHL1 expression may be a candidate for further study as a class discriminator. This suggests two possibilities with regard to recurrence; (i) that microscopic residual disease unidentifiable either by the surgeon or by current neuroimaging strategies may serve as a focus for early recurrence or that biological differences in recurrence phenotypes may occur outside of the transcriptome. These findings are useful for focusing future investigations into the clinical and biological mechanisms of PA recurrence as well as for development of strategies designed to predict prospectively these recurrence phenotypes.

Neurotrophins, their receptors and KI-67 in human GH-secreting pituitary adenomas: an immunohistochemical analysis

Pituitary adenomas are a diverse group of tumors arising from the pituitary gland. Typically, they are small, slow-growing, hormonally inactive lesions that come to light as incidental findings on radiologic or postmortem examinations, although some small, slow-growing lesions with excessive hormonal activity may manifest with a clinical syndrome. The family of neurotrophins plays a key role in the development and maintenance of the pituitary endocrine cell function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. The objective of our experimental study is to investigate the localization of the neurotrophins, their relative receptors and to detect the expression level of Ki-67 to determine whether all these factors participate in the transformation and development of human pituitary adenomas. A very strong expression of Neurotrophin-3 (NT-3) and its receptor TrKC was observed in the extracellular matrix (ECM) and vessel endothelium, together with a clear/marked presence of Brain-derived neurotrophic factor (BDNF), and its receptor TrKB, thus confirming their direct involvement in the progression of pituitary adenomas. On the contrary, NGF (Nerve growth factor) and its receptor TrKA and p75NTR were weakly expressed in the epithelial gland cells and the ECM.

Natural history of postoperative nonfunctioning pituitary adenomas: a systematic review and meta-analysis

OBJECTIVE

Previous studies attempting to define the natural history of postoperative nonfunctioning pituitary adenomas (pNFPAs) were somewhat limited by selection bias and/or small numbers and/or lack of consistency among the study findings. The aim of this study was to scrutinize the literature in order to analyze the natural history of pNFPAs.

METHODS

Electronic database including MEDLINE, PubMed and Cochrane CENTRAL were searched. The literature relating to the patients with pNFPAs without postoperative radiotherapy and pharmacotherapy was collected. Eligible studies reported on the rate of tumor recurrence, the tumor growth-free survival rate (TGFSR) at 5 and 10 years, and/or the residual tumor volume doubling time (TVDT).

RESULTS

19 studies met the criteria. The pNFPAs were divided into two groups: the pooled recurrence rate of group I without detectable residual tumor (371 patients) was 12% (95% CI 6-19%), the TGFSR at 5 and 10 years were 96% (95% CI 89-99%) and 82% (95% CI 65-94%), respectively. The pooled recurrence rate of group II with residual tumor (600 patients) was 46% (95% CI 36-56%), the TGFSR at 5 and 10 years were 56% (95% CI 41-71%) and 40% (95% CI 27-53%), respectively. The mean TVDT was 3.4 years (95% CI 2.4-4.5 years).

CONCLUSIONS

pNFPAs, with or without detectable residual tumor, need stratification of treatment and radiological/endocrinological follow-up strategy. According to the TVDT, residual tumor regrowth is very slow, which permits an extensive and safe follow-up program for most patients.

The role of radiation therapy in the management of non-functioning pituitary adenomas

Surgical removal of non-functioning pituitary adenoma (NFPA) is the first-choice therapeutic option, but radical removal of the tumor cannot be accomplished in all patients. The best strategy to prevent regrowth of NFPA is still a matter of debate. Adjuvant radiotherapy is very effective in reducing recurrence rate after incomplete removal of NFPA, but concerns still exist about long-term toxicity of radiation. Different modalities have been developed to irradiate the pituitary region. One major distinction is between radiation techniques that deliver the total dose in multiple sessions using 3 fixed radiation beams and radiosurgical equipment that delivers the total dose to the target volume in a single treatment session. Progression-free survival of patients with NFPA treated by adjuvant radiotherapy is well above 90% at 5 yr in most studies and diminishes only slightly at 10 yr. Very few studies have a more prolonged follow-up. In comparison, the 5- and 10-yr estimated recurrence rate without adjuvant radiotherapy ranged from 15% to 51% and from 44% to 78%, respectively. Complications of radiation include rare but severe side-effects, such as secondary brain neoplasm, optic neuropathy, cerebrovascular accidents, and more frequent but less severe complications, such as pituitary deficiency. Optimal management of patients with residual or recurring NFPA after surgical debulking can be achieved through the judicious use of different treatment options, necessitating close cooperation between neurosurgeons, endocrinologists, and radiation oncologists.

Therapeutic effect of retinoic acid on unilateral ureteral obstruction model

BACKGROUND

Retinoic acids, a group of natural and synthetic vitamin A derivatives, have potent anti-proliferative, anti-inflammatory and anti-fibrotic properties. We investigated the therapeutic effect of all-trans-retinoic acid (ATRA) on unilateral ureteral obstruction (UUO) model mice.

METHODS

First, to evaluate the prophylactic effect, we administered 0.5 mg of ATRA for 3 days before UUO (UUO ATRA). Then, to evaluate the therapeutic effects, we administered 0.5 mg of ATRA 3 days after UUO (Day 3 ATRA). We compared the histological changes and immunostaining of macrophages, α-smooth muscle actin (α-SMA) and collagen I, and mRNA expression of monocyte chemotactic protein-1 (MCP-1), transforming growth factor (TGF)-β(1) and TGF-β R-II by RT-PCR 7 days after UUO.

RESULTS

In the UUO ATRA and Day 3 ATRA groups, we observed a significant improvement in histological and immunological findings, including macrophage infiltration and improved expression of MCP-1, TGF-β(1), α-SMA and collagen I compared with the UUO Day 7 group.

CONCLUSION

ATRA treatment is not only an effective prophylactic strategy, but also a therapeutic strategy for the treatment of progressive renal fibrosis in diseased kidneys.

The clinical significance of MIB-1 labeling index in pituitary adenomas

Pituitary adenomas are unique in several ways--they are rarely malignant and yet can be invasive of several compartments. Recurrences in tumors with bland histological features that have been radically excised are a reason for frustration faced by endocrinologists and neurosurgeons in treatment of pituitary adenomas. Several attempts have therefore been made to determine the growth potential of pituitary adenomas. The aim of the present study was to define the biological significance of the MIB-1 labelling index (MIB-1 LI) in pituitary adenomas. The study included 159 cases of surgically treated pituitary adenoma seen in a single institution. MIB-1 LI was not found to be related to age or gender. The mean MIB-1 LI for clinically functional adenomas was marginally higher than that for clinically non-functional adenomas. There was a significant difference in the MIB-1 LI for tumors with a maximum diameter of more than 4 cm at a MIB-1 LI of ≥2%, however this difference was not statistically significant at a higher MIB-1 LI cut off value of >3%. The mean MIB-1 LI was significantly higher in tumors causing hydrocephalus and in those with cavernous sinus invasion and not when invasion was defined as invasion by tumor in any direction. We conclude that large pituitary macroadenomas, tumors filling the third ventricle causing hydrocephalus and tumors with true cavernous sinus invasions are more likely to have a higher proliferation index. Close follow up of tumors showing these imaging features would be recommended.

MIB-1 labeling index correlated with magnetic resonance imaging detected tumor volume doubling time in pituitary adenoma

OBJECTIVE

The purpose of this study was to evaluate whether MIB-1 labeling index (LI) could be used to predict growth velocity of residual pituitary adenomas after surgery.

MATERIALS AND METHODS

One hundred and sixty pituitary adenomas which had not received other treatment modality except for surgery were collected. Each of them had at least two post-operative magnetic resonance imaging (MRI) studies with an interval of at least 1 month apart. Tumor volume doubling time (TVDT) was calculated for those in which volume increased.

RESULTS

Post-operative tumor progression was noted in 54 (33.8%) cases, of which 39 (72.2%) cases were non-functioning adenomas. The MIB-1 LIs of the functioning and non-functioning adenomas were not significantly different. The median TVDT of these 54 cases was 34.6 months. The mean and median MIB-1 LI were 2.7 and 1.1 respectively (range 0.4-20.6). The MIB-1 LI was significantly correlated with log(2)(TVDT) (r=-0.363, P=0.007); when LI was <0.8, the TVDT of 90.5% cases was >or= 2 years.

CONCLUSIONS

Only one-third of the pituitary adenomas progressed after surgery, and their MIB-1 LIs were generally low. The MIB-1 LI was significantly correlated with the MRI detected TVDT of post-operative residual pituitary adenomas.

Determination of cell proliferation using Mcm2 antigen and evaluation of apoptosis and TGF-beta1 expression in GH-secreting or clinically nonfunctioning pituitary adenomas

Pituitary adenomas (PA) occasionally show aggressive behavior, with invasion of the surrounding tissues. The identification of markers able to recognize aggressive PA in early stages remains a challenge. We aimed to determine the expression of a new cell proliferation marker, Mcm2, and the presence of apoptosis in PA, and to evaluate the association of clinicopathological features with the apoptotic and proliferative indices. Additionally, the TGF-beta1 expression, an inducer of apoptosis, was determined. The proliferative index was determined in GH-secreting or clinically nonfunctioning PA using immunohistochemical (IH) methods for Mcm2 and Ki-67 antigens. The apoptosis was assessed by the TUNEL method and the TGF-beta1 expression by IH. A significant positive correlation was found between log Mcm2 index and log Ki-67 index (p < 0.001). Mcm2 and Ki-67 detected a similar number of proliferating cells. Mcm2 index showed a significant association with tumor extension (p = 0.02), but not with tumor invasion. Apoptosis was detected in 17% of the adenomas, with a maximum apoptotic index of 0.77%. Immunoreactivity to TGF-beta1 was observed in 77% of the adenomas, showing an association with tumor extension. We concluded that, in this sample, Mcm2 was similar to Ki-67 in the identification of the proliferating cells and that apoptosis was rare.

Ki-67 in pituitary neoplasms: a review--part I

KI-67, A MARKER of cellular proliferation, has been studied extensively in pituitary neoplasia. It is of relevance to various clinicopathological parameters, including tumor subtype, size, invasiveness, and recurrence, as well as patient age and sex. Generally, pituitary tumors behaving aggressively have increased Ki-67 labeling indices. Nonetheless, there is considerable overlap in Ki-67 labeling between noninvasive and invasive adenomas as well as between adenomas and pituitary carcinomas. Not only is there no general agreement regarding the relationship of Ki-67 labeling index and tumor invasiveness, but the same is also true of the association with pituitary tumor size, growth fraction, and recurrence. Whereas a number of studies found conclusive associations of Ki-67 labeling indices with aggressive behavior, size, and/or adenoma subtype, others fail to do so. It is evident that discrepant data regarding tumor behavior in part has its basis in nonuniform study criteria. For example, different investigators use varying criteria of tumor invasion and recurrence. Herein, we review the literature relating Ki-67 expression and various other clinicopathological parameters and conclude that uniform definitions and methods, as well as new markers, are key to improved treatment of pituitary tumors.

Residual nonfunctioning pituitary adenomas: prognostic value of MIB-1 labeling index for tumor progression

Object

In residual nonfunctioning pituitary adenomas, reliable prognostic parameters indicating probability of tumor progression are needed. The Ki 67 expression/MIB-1 labeling index (LI) is considered to be a promising candidate factor. The aim in the present study was to analyze the clinical usefulness of MIB-1 LI for prognosis of tumor progression.

Methods

The authors studied a cohort of 92 patients with nonfunctioning pituitary adenomas. Based on sequential postoperative MR images, patients were classified as tumor free (51 patients) or as harboring residual tumor (41 individuals). The residual tumor group was further subdivided in groups with stable residual tumors (14 patients) or progressive residual tumors (27 patients). The MIB-1 LI was assessed in tumor specimens obtained in all patients, and statistical comparisons of MIB-1 LI of the various subgroups were performed.

Results

. The authors found no significant difference of MIB-1 LI in the residual tumor group compared with the tumor-free group. However, MIB-1 LI was significantly higher in the progressive residual tumor group, compared with the stable residual tumor group. Additionally, the time period to second surgery was significantly shorter in residual adenomas showing an MIB-1 LI > 3%.

Conclusions

The data indicate that MIB-1 LI in nonfunctioning pituitary adenomas is a clinically useful prognostic parameter indicating probability of progression of postoperative tumor remnants. The MIB-1 LI may be helpful in decisions of postoperative disease management (for example, frequency of radiographic intervals, planning for reoperation, radiotherapy, and/or radiosurgery).

Relevance of Ki-67 and prognostic factors for recurrence/progression of gonadotropic adenomas after first surgery

OBJECTIVE

Gonadotropin-secreting pituitary adenomas carry a high risk of local recurrence or progression (R/P) of remnant tumor after first surgery. The clinical characteristics and the long-term outcome of these silent adenomas, which show no signs of endocrine hyperfunction, differ from those of other types of pituitary adenomas. However, to date, no study has focused specifically on gonadotropic adenomas.

MATERIALS AND METHODS

To identify prognostic factors of R/P of remnants, we studied the postoperative outcome of 32 gonadotropic pituitary adenomas, defined on immunohistochemical staining, according to their clinical and radiological characteristics as well as the Ki-67 labeling index (LI).

RESULTS

The Ki-67 LI failed to provide independent information for the identification of patients at risk of progression of remnants or recurrence. Multivariate survival analysis (Cox regression) showed that neither invasiveness nor remnant tumors nor hyposomatotropism influenced tumor recurrence. The strongest predicting factors of R/P were the antero-posterior (AP) diameter in the sagittal plane (P = 0.014), and the age of the patient at surgery (P = 0.047), with younger patients being at greater risk. Hazard ratios were 2.11 for each 5 mm increase in AP diameter and 0.57 for every 10 years of age.

CONCLUSION

The two simple clinical criteria revealed by our study, the AP diameter of the tumor and the age of the patient, should be helpful in planning clinical management and radiological monitoring after first surgery of gonadotropic adenomas, while awaiting the identification of other pathological parameters.

Relevance of high Ki-67 in pituitary adenomas

Pituitary adenomas are heterogeneous in growth rate, invasiveness, and recurrence. To understand the biological behavior of the individual adenoma more fully, cell proliferation markers such as monoclonal antibodies targeted against the Ki-67 antigen have been applied. The Ki-67 antigen is a protein related to cell proliferation and is expressed in cell nuclei throughout the entire cell cycle. The authors report the case of an extremely rapidly growing pituitary adenoma with cavernous sinus invasion. The lesion, which displayed a high Ki-67 labeling index (LI; 22%), was found in a 54-year-old woman who presented with diplopia and headaches. The patient underwent three transsphenoidal operations in less than 6 months and, ultimately, was treated with fractionated intensity-modulated radiation therapy. The relationships between high Ki-67 LIs and tumor recurrence, invasiveness, and growth velocity in pituitary adenomas are reviewed.

Clinical significance of Ki-67 labeling index in pituitary macroadenoma

The aim of our study was to investigate the correlation of the proliferative activity of pituitary neoplasms with clinical characteristics and recurrences. Tumor specimens were obtained from 44 consecutive patients with pituitary macroadenomas who underwent surgery between July 1998 and August 2003. Specimens were immediately fixed in 10% buffered formalin and then embedded in paraffin. The Ki-67 antigen was assessed by immumohistochemical analysis using the monoclonal antibody. We investigated the correlation of the Ki-67 labeling index with the following clinical and radiological characteristics: sex, age, presence or absence visual field defect, tumor classification, maximal tumor diameter, Hardy's classification, type of tumor, invasiveness, and recurrence. Our study suggests that the clinical characteristics such as visual field defect and recurrence are correlated with the high Ki-67 labeling index. No statistical differences were observed in the Ki-67 labeling index in relation to the following characteristics: sex, age, tumor classification, maximal tumor diameter, Hardy's classification, type of tumor, and invasiveness into the sphenoid sinus or cavernous sinus.

Measurement of Ki-67 antigen in 159 pituitary adenomas using the MIB-1 monoclonal antibody

Pituitary adenomas sometimes show rapid growth and recurrence, and about one third invade the structures surrounding the sella turcica. In an attempt to determine aggressive behavior at an early stage, we used the MIB-1 antibody to identify the Ki-67 antigen. The present study was designed to evaluate pituitary adenomatous tissue in terms of secretion and proliferation and to correlate the Ki-67 index with hormone phenotype and invasive behavior. Material from 159 patients submitted to one or more resections of pituitary adenomas was evaluated. Forty-two non-secretory adenomas and 43 adenomas immunoreactive for growth hormone, 19 for prolactin, 18 for growth hormone and prolactin, 16 for adrenocorticotropic hormone (ACTH), and 21 cases of plurihormonal/gonadotropin adenomas were detected by immunohistochemistry. The MIB-1 antibody was positive in 139 samples and the Ki-67 index ranged from 0.16 to 15.48% (mean = 1.22 +/- 2.09%), with no significant difference between genders, age groups, or secretory and non-secretory status. The Ki-67 index was higher in ACTH-secreting adenomas. Invasive pituitary adenomas had a significantly higher Ki-67 index (2.01 +/- 3.15%) than macroadenomas with or without supra-sellar extension (1.12 +/- 1.87%; P = 0.02). The index was not significantly different in the subgroup of adenomas with invasion of the cavernous sinus compared to groups with other types of invasion. We conclude that tumoral proliferative activity evaluated by the detection of the Ki-67 antigen is significantly higher in invasive than noninvasive adenomas, information which can be useful in therapeutic postoperative management since index cut-off values associated with aggressive behavior can be established.

Expression of Ki-67 antigen in nonfunctioning pituitary adenomas: correlation with growth velocity and invasiveness

Object. The cell cycle—dependent nuclear antigen Ki-67 is related to growth potential in a variety of tumors. Elevated expression of Ki-67 was previously shown in recurrent pituitary adenomas; however, it has remained unclear whether this expression is related to the growth velocity or invasive behavior of these tumors. The aim of this study was to determine the correlation of Ki-67 antigen expression, growth velocity, and invasiveness in nonfunctioning pituitary adenomas.

Methods. Between April 1998 and April 2002, 23 patients with nonfunctioning pituitary adenomas who had participated in an observation period in which multiple computerized tomography and magnetic resonance imaging studies had been performed were surgically treated in our department. Tumor volumes were assessed using a stereological method based on the Cavalieri principle. The growth rate was calculated for each patient. Expression of Ki-67 antigen was examined using the monoclonal antibody MIB-1.

The assessed growth velocity of the adenomas was best described by a linear growth model. The correlation between Ki-67 expression and growth rate was highly significant. Rapidly growing adenomas (>0.07% daily increase in size) were found to have a Ki-67 labeling index (LI) exceeding 1.5%, whereas all five adenomas with a very slow growth rate (< 0.02% daily increase in size) had a Ki-67 LI lower than 1.5%. No correlation was found between the growth rate and the invasive character of the adenomas.

Conclusions. Expression of Ki-67 antigen is significantly correlated to the growth velocity of pituitary adenomas. Invasive behavior is a feature independent of proliferative activity. The extent of Ki-67 expression is helpful for clinical decision making and routine assessment of Ki-67 is recommended during the histopathological workup of pituitary adenomas.

Growth pattern and rate in residual nonfunctioning pituitary adenomas: correlations among tumor volume doubling time, patient age, and MIB-1 index

OBJECT

Surgical cure can be achieved in pituitary adenomas when they are completely removed. It is controversial whether postoperative radiation therapy should be given to prevent recurrence, and whether an early reoperation should be performed for residual adenomas, because we have little information about the natural history of postoperative residual adenomas.

METHODS

The residual tumor volume was serially measured in 40 nonfunctioning pituitary adenomas (NFPAs) and the tumor volume doubling time (TVDT) was calculated. Correlations between the patients' age, tumor volume, log TVDT, and MIB-1 index were examined. Other factors including the patient's sex, cavernous sinus (CS) invasion by the tumor, or presence of an intratumoral cyst were analyzed to assess their influence on the TVDT. Values are expressed as the means +/- standard deviations. Thirty-eight adenomas increased in volume and two decreased during a follow-up period ranging from 4 to 141 months (mean 52.5 months). Exponentially linear tumor growth was observed in the 38 growing adenomas regardless of the residual tumor volume, with the TVDT ranging from 506 to 5378 days (mean 1836 days). The patients' age was 57.1 +/- 15.7 years (range 15-79 years), the tumor volume at the beginning of the magnetic resonance imaging observation period was 2.5 +/- 2.2 cm3 (range 0.07-14.5 cm3), and the MIB-1 index was 0.73 +/- 0.68% (range 0.1-2.9%). There was a correlation between the log TVDT and patient age (R = 0.73), an inverse correlation between the log TVDT and MIB-1 index (r = -0.49), and an inverse correlation between the MIB-1 index and patient age (r = -0.61). A significant difference (p = 0.0001) was noted between the TVDT (1,106 days) in the 19 patients younger than 61 years of age and the TVDT (2566 days) in the 19 patients who were 61 years of age or older. There was also a significant difference (p = 0.0002) between the age (50.8 +/- 15.3 years) of the patients with rapidly growing tumors (TVDT < 1,836 days, 24 patients) and the age (69.1 +/- 7.6 years) of the patients with slowly growing tumors (TVDT> 1836 days, 14 patients). Other factors including the patients' sex, CS invasion, and intratumoral cyst formation did not affect the TVDT of residual NFPAs.

CONCLUSIONS

The tumor growth rate of residual NFPAs is strongly influenced by the patient's age. The TVDT in elderly patients is much longer than that previously reported. Treatment strategies that take into consideration the natural history of residual adenomas should be established especially in the elderly population.

Surgical treatment of pituitary tumors in the elderly: clinical outcome and long-term follow-up

Pituitary adenomas in the elderly represent an increasing proportion of pituitary tumors, making the surgical management of these patients of special importance. We therefore decided to review our experience with transsphenoidal surgery (TSS) in this age group, in order to better evaluate its efficacy, safety and outcome. A retrospective study was performed on 39 patients aged more than 70 years at the time of surgery (mean age 74.1 +/- 2.9 years) and with a minimum follow-up duration of 4 years at the time of the study. Thirty-one had a nonfunctioning pituitary adenoma, 5 had a GH-secreting adenoma and 3 a macroprolactinoma, respectively. The commonest presenting symptom was visual deterioration (60%), whereas hypopituitarism were present in 41% of patients. All patients underwent TSS without any major peri- and post-operative complications. Visual fields improved in 74% of patients. Post-operative radiotherapy was performed in 17 patients with partial surgical resection and/or persistent hormonal hypersecretion, whereas 22 patients with subtotal or total surgical resection were treated by surgery only. Long-term follow-up (mean 9.1 +/- 2.7 years) showed evidence for tumor regrowth in one irradiated (5.9%) and 3 non-irradiated patients (13.6%), respectively. A noticeable complication of radiotherapy was progressive hypopituitarism, which worsened or developed in 65% of patients. We conclude that TSS is safe and well tolerated even in elderly patients, with a low incidence of minor complications. The indications for post-operative radiotherapy in patients with incomplete tumor resection should be better defined.

Anterior pituitary adenomas in patients aged more than 65 years: analysis of growth fraction (using the MIB-1 monoclonal antibody) and of clinical features in comparison to younger patients

AIMS AND BACKGROUND

The incidence of pituitary adenomas (PA). in patients aged more than 65 years is relatively low. The goal of this study was to evaluate the growth fraction and the clinical features of PA affecting old patients and to compare the results to those of younger subjects.

METHODS

We evaluated the Ki-67 LI using the monoclonal antibody MIB-1 in 21 patients of more than 65 years of age affected by PA consecutively operated on and compared the mean LI with that one of 104 patients under 65 operated on in the same period. The clinical behavior of PA was also analyzed in both groups.

RESULTS

In older cases PA occurred more frequently with visual disturbances: 17 out of 21 (80.9%) older patients showed pre-operative visual disturbances, versus 43 out of 104 (41.3%) younger patients (P=0.0009). Fifteen out of 21 (71.4%) older patients had a non-functioning PA, versus 38 out of 66 (36.5%) younger patients (P=0.003). In relation to surgically verified infiltration of sellar floor dura and bone, we identified non-invasive (12/21 older cases) and invasive (9 cases) adenomas; the wall of the cavernous sinus was infiltrated in 5 cases. The overall mean Ki-67 LI was 4.06+/-6.73 versus 2.35+/-2.54% of younger patients (P=0.04).

CONCLUSIONS

Our data confirm that Ki-67 LI detected by the MIB-1 monoclonal antibody is a useful marker in the determination of the growth fraction of PA. In relation to our preliminary results, PA in the elderly seem to have a higher growth fraction than in younger patients, are more often non-functioning and occur frequently with visual disturbances. In order to confirm our data further larger studies are necessary.

Endocrine inactive and gonadotroph adenomas: diagnosis and management

Endocrine inactive pituitary adenomas represent about one quarter of all pituitary tumors. By immunocytochemistry, most of these tumors are positive for intact gonadotropins and/or their subunits. Clinical presentation is usually secondary to mass effect symptoms, such as visual disturbances, headache, and hypopituitarism. Differential diagnosis is usually accomplished by neuroradiologic studies, even though in selected cases positron emission tomography and/or single photon emission tomography may aid to distinguish pituitary adenomas from other endocrine inactive lesions, such as meningiomas and craniopharyngiomas. Surgical management is usually considered the first choice treatment for patients with endocrine inactive pituitary adenomas because it is very effective in ameliorating symptoms of chiasmal compression and headache. Radical removal of the tumor, however, is difficult to obtain because of the frequent invasiveness into the cavernous sinus. Radiation therapy diminishes the likelihood of tumor recurrence, especially in patients with demonstrable tumor remnants after surgery. Medical therapy with dopaminergic drugs, somatostatin analogs, or gonadotropin-releasing hormone agonists or antagonists causes mild reduction of tumor size in few patients and, therefore, seems to be of limited value in the therapeutic management of patients with endocrine inactive pituitary adenomas.

Lack of correlation between Ki-67 labelling index and tumor size of anterior pituitary adenomas

AIMS AND BACKGROUND

The Ki-67 is a nuclear antigen detected by the monoclonal antibody MIB-1 and its Labeling Index (LI) is considered a marker of normal and abnormal cell proliferation. Pituitary adenomas are generally well differentiated neoplasms, even if in about one third of cases they are invasive of surrounding tissues. The aim of this study is to evaluate the correlation between Ki-67 labelling index and tumor size of pituitary adenomas extimated by means CT and MRI and confirmed at operation.

METHODS

Using the monoclonal antibody MIB-1, we evaluated the expression of Ki-67 in 121 anterior pituitary adenomas consecutively operated on in a 48-month period.

RESULTS

In relation to neuroradiological (CT and MRI) and surgically verified tumor size, we identified 24 microadenomas, 27 intrasellar macroadenomas, 34 intra-suprasellar macroadenomas, and 36 intra-supra-parasellar macroadenomas. The adenomas were non-infiltrating (76 cases) and infiltrating (45 cases) adenomas. The wall of the cavernous sinus (CS) was infiltrated in 18 cases. Forty-eight adenomas were non-functioning and 73 functioning. The overall mean +/- SD Ki-67 LI was 2.72 +/- 2.49% (median 1.6). It was 2.59 +/- 1.81 in microadenomas, 2.63 +/- 3.45 in intrasellar macroadenomas, 1.91 +/- 2.11 in intra-suprasellar macroadenomas, and 3.29 +/- 5.45 in intra-supra-parasellar macroadenomas (p = 0.27). It was 3.73 +/- 5.13% in infiltrating and 2.03 +/- 2.41% in non-infiltrating adenomas (p = 0.02), and 5.61 +/- 7.19% in CS-infiltrating versus 2.09 +/- 2.37% in CS-non-infiltrating adenomas (p = 0.0005).

CONCLUSIONS

Our preliminary results seem to exclude significative correlations between Ki-67 LI and tumor size of anterior pituitary adenomas, even if this index can be considered a useful marker in the determination of the infiltrative behaviour of these tumors.

Relationships among DNA Index, S-Phase, and invasive behavior in anterior pituitary adenomas. A cytometric study of 61 cases with Feulgen-positive DNA analysis

BACKGROUND

Pituitary adenomas are usually well differentiated neoplasms, although in about 1/3 of cases they invade the surrounding dura mater and bone, as confirmed by surgical findings, resulting in a long-term possibility of relapse.

METHODS

To identify the cellular growth rate and to correlate it with surgical evidence of invasiveness, we performed the analysis of DNA with static cytometric quantitation on fresh surgical specimens, using a computer-assisted image processor. The DNA index and the percentage of cells in S-phase (%SPh) were obtained in 61 pituitary tumors consecutively operated on. In relation to surgically verified infiltration of dura and bone, we identified 39 noninvasive and 22 invasive adenomas. The cavernous sinus (CS) was infiltrated in 13 cases. On the basis of immunohistochemical staining and endocrine activity we recognized 27 nonsecreting and 34 secreting adenomas.

RESULTS

The DNA content was aneuploid in 33 cases (11 nonfunctioning, 22 functioning; p = 0.05); there was no correlation with the invasive behavior of the adenomas. The DNA index ranged between 0.93 and 2.50 (median 1.13); the range of %SPh was 0-12.00% (median 2.54%). In invasive adenomas the mean DNA index was 1.33 (p not significant) and the mean %SPh was 4.03% (p = 0.05). In CS-infiltrating pituitary adenomas, the mean DNA index was 1.44 (p = 0.04) and the mean %SPh was 4.52% (p = 0.05).

CONCLUSIONS

Our preliminary results seem to reveal a correlation between DNA index, %SPh, and invasive behavior of pituitary adenomas, encouraging the use of DNA analysis in the prognostic evaluation of these tumors.

Recurrence in pituitary adenomas in childhood and adolescence

Pediatric pituitary adenomas are thought to behave more aggressively than their adult counterparts, and the ability to predict the degree of such behavior remains elusive. Proliferation marker Ki-67 and tumor suppressor gene p53 mutations have been used in adults to assist in the evaluation of invasiveness and recurrence; however, their use in childhood and adolescence remains anecdotal. Our study evaluates the proliferative potential in pituitary adenomas of five patients and its relationship with recurrence or persistence of endocrinologic or clinical abnormalities. For such assessment, tissues were stained with monoclonal antibodies BP53-12 forp53 tumor suppressor gene mutation and MIB-1, which binds to cell cycle-specific nuclear antigen Ki-67. In our series, one patient with recurrent adenoma demonstrated the highest (50%) p53 immunoreactivity. Ki-67-stained nuclei ranged from 0 to 2%, failing to identify the recurrent tumor. Therefore, p53 immunoreactivity, rather than Ki-67 nuclear stain, may be useful for identification of recurrent pituitary adenomas in childhood and adolescence.

Proliferation Index of Nonfunctioning Pituitary Adenomas: Correlations with Clinical Characteristics and Long-term Follow-up Results

OBJECTIVE

The recurrence of nonfunctioning pituitary adenomas (NFPAs) after surgical removal is common. The aim of our study was to investigate and correlate the growth fraction of NFPAs with clinical characteristics and long-term follow-up results.

METHODS

Tumor specimens were obtained from 101 consecutive patients with NFPAs (48 female patients and 53 male patients; mean age, 52.0 ± 1.5 yr). Specimens were immediately fixed in 10% buffered formalin and then embedded in paraffin. The Ki-67 antigen was assessed by immunocytochemical analysis using the monoclonal antibody MIB-1. The Ki-67 antigen labeling index (LI) was determined by counting a total of at least 1000 neoplastic nuclei.

RESULTS

The mean Ki-67 LI for the 101 patients was 2.4 ± 0.3% (range, 0–23.0%). Only age at surgery was inversely correlated with the Ki-67 LI; sex, maximal tumor diameter, and invasiveness into the cavernous sinuses did not significantly affect the Ki-67 LI. The mean follow-up period was 39.7 ± 2.1 months. During follow-up monitoring, 23 patients experienced tumor recurrence, after a mean period of 28.6 ± 4.8 months. Invasiveness of the tumor on preoperative magnetic resonance imaging scans was the strongest predictor of late tumor recurrence, followed by previous pituitary surgery, younger age, and lack of postoperative radiotherapy. The Ki-67 LI had no independent prognostic value.

CONCLUSION

Our study suggests that the clinical characteristics of patients with NFPAs, except for age at surgery, are not correlated with the Ki-67 LI. Moreover, the Ki-67 LI does not seem to provide independent information to identify patients at high risk for tumor recurrence.

Mitosis and apoptosis in the pituitary gland: tumour formation or hyperplasia?

Direct analyses of trophic activity in the pituitary have been hampered by the lack of normal human tissue to study and by the short duration of the histologically overt phases of mitosis and apoptosis, which renders significant trophic events difficult to quantify. In rats and dogs, pituitary cell turnover is rapid in youth, declines markedly with age and virtually ceases by 'late middle age'. Specific stimuli superimpose brief but dramatic trophic events on this active background. There is little convincing evidence, as yet, for plasticity, i.e. the persistence of cell population changes after transient stimuli have passed. In contrast to spontaneous pituitary adenomas in rats, human pituitary tumours show relatively modest increases in mitotic activity. In the light of these observations, this chapter examines the accepted models of pituitary adenoma formation and propagation, with special reference to trophic activity, clonality and tumour behaviour.

Invasive pituitary adenomas: significance of proliferation parameters

Although most pituitary adenomas behave in a purely benign fashion, microscopic invasion of the subjacent dura is very common, and clinically overt infiltration of the surrounding dura and bone is apparent at intraoperative inspection in about one third of cases. The factors governing invasive behavior remain unknown but are believed to be separate from those regulating cell proliferation. Histological features alone do not distinguish between benign, invasive, and malignant tumors of adenohypophyseal origin. Multiple attempts have been made to identify prognostic markers of aggressive behavior among these tumors. They include cytogenetic analysis of putative tumor suppressor genes or proto-oncogenes as well as immunohistochemical detection of cell-cycle specific antigens. At present, however, these analyses can neither distinguish the indolent pituitary adenoma from one that will pursue an invasive course, nor reliably predict the prognosis in individual patients.

The effects of age and spontaneous adenoma formation on trophic activity in the rat pituitary gland: a comparison with trophic activity in the human pituitary and in human pituitary adenomas

The effects of ageing on trophic activity in the pituitary gland and the molecular events that underlie pituitary tumour formation are poorly understood. In the present study we have used an extremely accurate system to analyse trophic activity in human pituitary tumours and compared our findings with trophic activity in spontaneous rat pituitary adenomas and with changes in basal rates of turnover as the animals age. Thin, hematoxylin and eosin-stained pituitary sections from groups of male Wistar rats aged 6 weeks to 16 months, killed at 90-min intervals after receiving a single intraperitoneal bolus of colchicine to block cellular passage through mitosis, were evaluated histologically. Extremely accurate quantification of small changes in the prevalence of trophic events, and thus the rate of cell turnover, was achieved using a dedicated computerized aid to manual cell counting. Results were compared with the prevalence of mitotic activity in 24 spontaneous rat pituitary adenomas and with a series of 97 archival human pituitary adenomas and 24 normal human pituitary glands obtained at autopsy. In rats, average basal pituitary cell turnover declined by over 95% between 6 weeks and 16 months of age. Concurrent with this decline was a marked increase in the prevalence of adenoma formation. The prevalence of mitotic activity in spontaneous rat pituitary adenomas averaged almost twice that seen in normal, young rat pituitary and exceeded 16 times that seen in the pituitary of aged animals. In contrast, when compared to normal human pituitary tissue, average trophic activity in human pituitary adenomas remained extremely low.

Ki-67 labelling index and invasiveness among anterior pituitary adenomas: analysis of 103 cases using the MIB-1 monoclonal antibody

AIMS

To investigate the relation between proliferative activity of anterior pituitary adenomas, quantified by the Ki-67 labelling index, and their invasive behaviour.

METHODS

Expression of Ki-67 was evaluated in 103 anterior pituitary adenomas consecutively operated on in a 36 month period and correlated with surgical evidence of invasiveness.

RESULTS

Non-invasive (n = 65) and invasive (n = 38) adenomas were identified from surgically verified infiltration of sellar floor dura and bone. The wall of the cavernous sinus was infiltrated in 16 cases. Forty one adenomas were non-functioning and 62 functioning (24 prolactin, 21 growth hormone, 10 ACTH, seven mixed). The overall mean (SD) Ki-67 labelling index was 2.64 (3.69) per cent (median 1.5). The mean index was 3.08 (4.59) per cent in functioning and 1.97 (1.78) per cent in non-functioning tumours; 5.47 (9.52) per cent in ACTH adenomas and 2.33 (2.42) per cent in others (p = 0.01); 3.71 (5.17) per cent in invasive and 2.01 (2.45) per cent in non-invasive adenomas (p = 0.027); and 5.58 (7.24) per cent in cavernous sinus infiltrating v 2.10 (2.39) per cent in cavernous sinus non-infiltrating adenomas (p = 0.0005). To identify a value of labelling index beyond which adenomas should be considered invasive and another beyond which cavernous sinus infiltration should be suspected, normality Q-Q plots were obtained: a threshold labelling index of 3.5% for invasive adenomas and of 5% for cavernous sinus infiltrating adenomas was defined, with statistically significant differences (p = 0.02 and p = 0.004, respectively).

CONCLUSIONS

The Ki-67 labelling index can be considered a useful marker in determining the invasive behaviour of anterior pituitary adenomas.