Subtyping does matter in pituitary adenomas

New WHO classification of pituitary adenomas (4th edition): assessment of pituitary transcription factors and the prognostic histological factors

WHO classification of pituitary adenomas was revised in 2017. The two major and significant changes are discussed. (1) The new classification focuses on adenohypophysial-cell lineage for the designation of adenomas, and thus, assessment of pituitary transcription factors is recommended. Its appropriate use has a complementary role in obtaining an accurate diagnosis, particularly in hormone-negative adenomas. Subclassification of nonfunctioning adenomas was revised accordingly and, consequently, null cell adenomas became quite rare. (2) "Atypical adenoma", a previous category, was eliminated due to the poor reproducibility and predictive value. Assessment of tumor proliferation marker and other clinical parameters such as invasion are recommended to predict aggressiveness. "High-risk adenomas" are those with rapid growth, radiological invasion, and a high Ki-67 proliferation index, whereas some special adenoma subtypes commonly show aggressive behavior.

Implications of the World Health Organization definition of atypia on surgically treated functional and non-functional pituitary adenomas

BACKGROUND

The World Health Organization (WHO) defines atypical pituitary adenomas as tumours with a MIB-1 labelling index ≥3%, p53 positivity and increased mitotic activity. Although a few reports have described the clinical and radiological correlates of atypia in pituitary adenomas, its impact on postoperative outcomes is not clearly defined.

METHOD

We reviewed preoperative and postoperative records of patients undergoing surgery for pituitary adenomas. Postoperative outcomes for functional adenomas (FPAs) were assessed according to contemporary definitions of remission and recurrence. For non-functional pituitary adenomas (NFPAs), extent of resection and disease progression were defined on the basis of postoperative magnetic resonance imaging.

RESULTS

Of 394 patients included for analysis, 29 cases (7.4%) fulfilled criteria for atypia. Patients with atypical tumours were significantly younger than those with typical adenomas. Remission was possible in 47.4% of FPAs, and was unrelated to the presence of atypia. In NFPAs, local invasiveness was negatively associated with extent of resection (OR, 0.255; 95% CI, 0.086-0.753; p < 0.001). In 93 NFPAs followed postoperatively with serial imaging over a mean duration of 37.5 months, disease progression/recurrence was significantly associated with the presence of atypia (OR, 5.058; 95% CI, 1.273-20.098; p = 0.021) on multivariate analysis.

CONCLUSIONS

Patients with atypical non-functional pituitary adenomas are at risk for postoperative recurrence and disease progression, suggesting a need for adjuvant therapy. However, only a small fraction of pituitary tumours demonstrate atypia, as defined by the WHO, limiting its clinical utility.

The Predictive Value of Pathologic Features in Pituitary Adenoma and Correlation with Pituitary Adenoma Recurrence

Background

The 2004 World Health Organization classification introduced atypical pituitary adenoma (aPA), which was equivocally defined as invasion with increased mitotic activity that had a Ki-67 labeling index (LI) greater than 3%, and extensive p53 immunoreactivity. However, aPAs that exhibit all of these features are rare and the predictive value for recurrence in pituitary adenomas (PAs) remains uncertain. Thus, we sought to characterize pathological features of PAs that correlated with recurrence.

Methods

One hundred and sixty-seven cases of surgically resected PA or aPA were retrieved from 2011 to 2013 in Seoul St. Mary’s Hospital. Among them, 28 cases were confirmed to be recurrent, based on pathologic or radiologic examination. The pathologic characteristics including mitosis, invasion, Ki-67 LI and p53 immunoreactivity were analyzed in relation to recurrence.

Results

Analysis of the pathologic features indicated that only Ki-67 LI over 3% was significantly associated with tumor recurrence (p = .02). The cases with at least one pathologic feature showed significantly higher recurrence rates (p < .01). Analysis indicated that cases with two pathologic features, Ki-67 LI over 3% and extensive p53 immunoreactivity 20% or more, were significantly associated with tumor recurrence (p < .01).

Conclusions

Based on these results, PA tumor recurrence can be predicted by using mitosis, invasion, Ki-67 LI (3%), or extensive p53 immunoreactivity (≥ 20%). Assessment of these features is recommended for PA diagnosis for more accurate prediction of recurrence.

Atypical pituitary adenomas: clinical characteristics and role of ki-67 and p53 in prognostic and therapeutic evaluation. A series of 50 patients

The aim of the study was to assess incidence rate, hormonal activity, and local invasiveness and evaluate outcomes of so-diagnosed atypical pituitary adenomas that underwent endoscopic endonasal surgery at the Division of Neurosurgery of Università degli Studi di Napoli Federico II. According to the 2004 WHO classification, atypical pituitary adenomas are defined by an invasive growth, Ki-67/MIB-1 proliferative index greater than 3 %, high p53 immunoreactivity, and increased mitotic activity. A retrospective analysis of a series of 434 pituitary adenomas that underwent endoscopic endonasal surgery at our department between March 2007 and February 2013 was performed. Fifty adenomas (11.5 %) met the criteria of diagnosis of atypical lesions; 10 (21.6 %) of the 50 patients were recurrent tumors with a previous transsphenoidal surgery. Forty-one (82 %) were macroadenomas, and 21/50 (42 %) showed a clear invasion of the cavernous sinus. Histotype of atypical adenomas figured out to be nonfunctioning in 23 cases (46 %), PRL secreting in 10 cases (20 %), ACTH secreting and GH secreting each apart in 8 patients (16 %), and in a single case a GH/PRL secreting adenoma (2 %). The Ki-67 labeling index ranged from 3.5 to 22.5 % (mean 5.6 %). Tumor recurrence was observed in six cases (12 %) after a mean time of 18 months (range 9-24 months). Mean follow-up was 36.5 months (range 2-80 months). Atypical pituitary adenomas account for ca. 10 % of all pituitary adenomas; these lesions have peculiar features. It should be considered that a strong immunopositivity of p53 and higher Ki-67 LI could predict an increased risk of tumor recurrence, but more studies and larger series are expected to confirm and enlarge the diagnostic and therapeutic management process of these lesions.

Steroidogenic Factor 1, Pit-1, and Adrenocorticotropic Hormone: A Rational Starting Place for the Immunohistochemical Characterization of Pituitary Adenoma

Context.—Pituitary adenoma classification is complex, and diagnostic strategies vary greatly from laboratory to laboratory. No optimal diagnostic algorithm has been defined.

Objective.—To develop a panel of immunohistochemical (IHC) stains that provides the optimal combination of cost, accuracy, and ease of use.

Design.—We examined 136 pituitary adenomas with stains of steroidogenic factor 1 (SF-1), Pit-1, anterior pituitary hormones, cytokeratin CAM5.2, and α subunit of human chorionic gonadotropin. Immunohistochemical staining was scored using the Allred system. Adenomas were assigned to a gold standard class based on IHC results and available clinical and serologic information. Correlation and cluster analyses were used to develop an algorithm for parsimoniously classifying adenomas.

Results.—The algorithm entailed a 1- or 2-step process: (1) a screening step consisting of IHC stains for SF-1, Pit-1, and adrenocorticotropic hormone; and (2) when screening IHC pattern and clinical history were not clearly gonadotrophic (SF-1 positive only), corticotrophic (adrenocorticotropic hormone positive only), or IHC null cell (negative-screening IHC), we subsequently used IHC for prolactin, growth hormone, thyroid-stimulating hormone, and cytokeratin CAM5.2.

Conclusions.—Comparison between diagnoses generated by our algorithm and the gold standard diagnoses showed excellent agreement. When compared with a commonly used panel using 6 IHC for anterior pituitary hormones plus IHC for a low-molecular-weight cytokeratin in certain tumors, our algorithm uses approximately one-third fewer IHC stains and detects gonadotroph adenomas with greater sensitivity.

Typical and atypical pituitary adenomas: a single-center analysis of outcome and prognosis

BACKGROUND AND OBJECTIVE

In 2004, the World Health Organization defined atypical pituitary adenomas as those with a Ki-67 expression > 3%, an excessive p53 expression and increased mitotic activity. As the usefulness of this classification is controversial, we reviewed typical and atypical pituitary adenomas to compare the clinical and prognostic features.

PATIENTS AND METHODS

We retrospectively reviewed 343 consecutive pituitary adenomas. Atypical pituitary adenomas represented 18.7% of cases. All patients were operated on at the Department of Neurosurgery of our institution and were followed up at the Hypothalamic-Pituitary Disease Unit of the same institution. The median follow-up time was 75 months (range 7-345).

RESULTS

Younger age at diagnosis as well as immunohistochemical positivity for adrenocorticotropic hormone and prolactin correlated with a higher risk of atypical pituitary adenomas, whereas typical and atypical pituitary adenomas did not differ with regard to gender, tumor size, recurrence risk and disease-free survival time (DFST). Among the 219 patients who underwent radical surgery, a Ki-67 expression ≥ 1.5% was associated with a higher risk of recurrence and a worse DFST, even after correction for age at diagnosis, gender, immunohistochemical classification, tumor size, invasiveness and Knosp classification [p = 0.01; hazard ratio (HR) 2.572; 95% confidence interval (CI) 1.251-5.285). Pituitary adenomas with a Ki-67 expression ≥ 1.5% showed a worse DFST as compared to pituitary adenomas with a Ki-67 expression < 1.5% (HR 2.166; 95% CI 1.154-4.064).

CONCLUSION

In this series, atypical and typical pituitary adenomas did not differ with regard to recurrence and DFST. Pituitary adenomas with a Ki-67 expression ≥ 1.5% showed a higher recurrence risk and a worse DFST as compared to those with a Ki-67 expression < 1.5%. We suggest that a Ki-67 expression ≥ 1.5% may be useful as a prognostic marker, though this will need to be confirmed by prospective, multicenter data.

Atypical pituitary adenomas: incidence, clinical characteristics, and implications

Object

The 2004 WHO classification of pituitary adenomas now includes an “atypical” variant, defined as follows: MIB-1 proliferative index greater than 3%, excessive p53 immunoreactivity, and increased mitotic activity. The authors review the incidence of this atypical histopathological subtype and its correlation with tumor subtype, invasion, and surgical features.

Methods

The records of 121 consecutive patients who underwent transsphenoidal surgery for pituitary adenomas during an 18-month period were retrospectively reviewed for evidence of atypical adenomas.

Results

Eighteen adenomas (15%) met the criteria for atypical lesions; 17 (94%) of the 18 were macroadenomas. On imaging, 15 (83%) demonstrated imaging evidence of surrounding invasion, compared with 45% of typical adenomas (p = 0.004). Atypical tumors occurred in 12 female (67%) and 6 male (33%) patients. Patient age ranged from 16 to 70 years (mean 48 years). Nine patients (50%) had hormonally active tumors, and 9 had nonfunctional lesions. Four (22%) of the 18 patients presented to us with recurrent tumors. Immunohistochemical analysis demonstrated the following tumor subtypes: GH-secreting adenoma with plurihormonal staining (5 patients [28%]); null-cell adenoma (5 patients [28%]); silent ACTH tumor (3 patients [17%]), ACTH-staining tumor with Cushing's disease (2 patients [11%]), prolactinoma (2 patients [11%]), and silent FSH-staining tumor (1 patient [6%]). The MIB-1 labeling index ranged from 3% to 20% (mean 7%).

Conclusions

Atypical tumors were identified in 15% of resected pituitary adenomas, and they tended to be aggressive, invasive macroadenomas. More longitudinal follow-up is required to determine whether surgical outcomes, potential for recurrence, or metastasis of atypical adenomas vary significantly from their typical counterparts.

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.