Interobserver agreement of proliferation index (Ki-67) outperforms mitotic count in pulmonary carcinoids

Assessment of the current and emerging criteria for the histopathological classification of lung neuroendocrine tumours in the lungNENomics project

BACKGROUND

Six thoracic pathologists reviewed 259 lung neuroendocrine tumours (LNETs) from the lungNENomics project, with 171 of them having associated survival data. This cohort presents a unique opportunity to assess the strengths and limitations of current World Health Organization (WHO) classification criteria and to evaluate the utility of emerging markers.

PATIENTS AND METHODS

Patients were diagnosed based on the 2021 WHO criteria, with atypical carcinoids (ACs) defined by the presence of focal necrosis and/or 2-10 mitoses per 2 mm2. We investigated two markers of tumour proliferation: the Ki-67 index and phospho-histone H3 (PHH3) protein expression, quantified by pathologists and automatically via deep learning. Additionally, an unsupervised deep learning algorithm was trained to uncover previously unnoticed morphological features with diagnostic value.

RESULTS

The accuracy in distinguishing typical from ACs is hampered by interobserver variability in mitotic counting and the limitations of morphological criteria in identifying aggressive cases. Our study reveals that different Ki-67 cut-offs can categorise LNETs similarly to current WHO criteria. Counting mitoses in PHH3+ areas does not improve diagnosis, while providing a similar prognostic value to the current criteria. With the advantage of being time efficient, automated assessment of these markers leads to similar conclusions. Lastly, state-of-the-art deep learning modelling does not uncover undisclosed morphological features with diagnostic value.

CONCLUSIONS

This study suggests that the mitotic criteria can be complemented by manual or automated assessment of Ki-67 or PHH3 protein expression, but these markers do not significantly improve the prognostic value of the current classification, as the AC group remains highly unspecific for aggressive cases. Therefore, we may have exhausted the potential of morphological features in classifying and prognosticating LNETs. Our study suggests that it might be time to shift the research focus towards investigating molecular markers that could contribute to a more clinically relevant morpho-molecular classification.

Prognostic Immunohistochemistry for Ki-67 and OTP on Small Biopsies of Pulmonary Carcinoid Tumors: Ki-67 Index Predicts Progression-free Survival and Atypical Histology

Prognostic stratification of pulmonary carcinoids into "typical" and "atypical" categories requires examination of large tissue volume. However, there is a need for tools that provide similar prognostic information on small biopsy samples. Ki-67 and OTP immunohistochemistry have shown promising prognostic value in studies of resected pulmonary carcinoids, but prognostic value when using biopsy/cytology specimens is unclear. Ki-67 immunohistochemistry was performed on small biopsy/cytology specimens from pulmonary carcinoid tumors (n=139), and labeling index was scored via automated image analysis of at least 500 cells. OTP immunohistochemistry was performed on 70 cases with sufficient tissue and scored as positive or negative (<20% tumor nuclei staining). Higher Ki-67 index was associated with worse disease-specific progression-free survival (ds-PFS), with 3% and 4% thresholds having similarly strong associations with ds-PFS ( P <0.001, hazard ratio ≥11). Three-year ds-PFS was 98% for patients with Ki-67 <3% and 89% for patients with Ki-67≥3% ( P =0.0006). The optimal Ki-67 threshold for prediction of typical versus atypical carcinoid histology on subsequent resection was 3.21 (AUC 0.68). Negative OTP staining approached significance with atypical carcinoid histology ( P =0.06) but not with ds-PFS ( P =0.24, hazard ratio=3.45), although sample size was limited. We propose that Ki-67 immunohistochemistry may contribute to risk stratification for carcinoid tumor patients based on small biopsy samples. Identification of a 3% hot-spot Ki-67 threshold as optimal for prediction of ds-PFS is notable as a 3% Ki-67 threshold is currently used for gastrointestinal neuroendocrine tumor stratification, allowing consideration of a unified classification system across organ systems.

Updates on lung neuroendocrine neoplasm classification

Lung neuroendocrine neoplasms (NENs) are a heterogeneous group of pulmonary neoplasms showing different morphological patterns and clinical and biological characteristics. The World Health Organisation (WHO) classification of lung NENs has been recently updated as part of the broader attempt to uniform the classification of NENs. This much-needed update has come at a time when insights from seminal molecular characterisation studies revolutionised our understanding of the biological and pathological architecture of lung NENs, paving the way for the development of novel diagnostic techniques, prognostic factors and therapeutic approaches. In this challenging and rapidly evolving landscape, the relevance of the 2021 WHO classification has been recently questioned, particularly in terms of its morphology-orientated approach and its prognostic implications. Here, we provide a state-of-the-art review on the contemporary understanding of pulmonary NEN morphology and the potential contribution of artificial intelligence, the advances in NEN molecular profiling with their impact on the classification system and, finally, the key current and upcoming prognostic factors.

In-depth analysis of immunohistochemistry concordance in biopsy-resection pairs of bronchial carcinoids

Primary diagnosis of bronchial carcinoids (BC) is always made on biopsies and additional immunohistochemistry (IHC) is often necessary. In the present study we investigated the concordance of common diagnostic (synaptophysin, chromogranin, CD56 and INSM-1) and potential prognostic (OTP, CD44, Rb and p16) IHC markers between the preoperative biopsies and resections of in total 64 BCs, 26 typical (41 %) and 38 atypical (59 %) carcinoid tumors. Synaptophysin and chromogranin had 100 % concordance in all resected carcinoids and paired diagnostic biopsies. Synaptophysin was not affected by variable expression in biopsies compared to chromogranin, CD56 and INSM-1. Notably, INSM-1 IHC was false negative in 8 % of biopsies. Of the novel and potential prognostic markers, only CD44 showed 100 % concordance between biopsies and resections, while OTP showed two (4 %) false negative results in paired biopsies. While Rb IHC was false negative in 8 % of biopsies, no strong and diffuse pattern of p16 expression was observed. In this study, most false negative IHC results (85 %, 22/26) were observed in small flexible biopsies. Taken together, our data suggest excellent concordance of synaptophysin and CD44 on the preoperative biopsy samples, while other neuroendocrine markers, Rb and OTP should be interpreted with caution, especially in small biopsies.

Lung carcinoid tumours: histology and Ki-67, the eternal rivalry

WHO classification of Thoracic Tumours defines lung carcinoid tumours (LCTs) as well-differentiated neuroendocrine neoplasms (NENs) classified in low grade typical (TC) and intermediate grade atypical carcinoids (AC). Limited data exist concerning protein expression and morphologic factors able to predict disease aggressiveness. Though Ki-67 has proved to be a powerful diagnostic and prognostic factor for Gastro-entero-pancreatic NENs, its role in lung NENs is still debated. A retrospective series of 370 LCT from two oncology centers was centrally reviewed. Morphology and immunohistochemical markers (Ki-67, TTF-1, CD44, OTP, SSTR-2A, Ascl1, and p53) were studied and correlated with Overall Survival (OS), Cancer-specific survival (CSS) and Disease-free survival (DFS). Carcinoid histology was confirmed in 355 patients: 297 (83.7%) TC and 58 (16.3%) AC. Ki-67 at 3% was the best value in predicting DFS. Ki-67 ≥ 3% tumours were significantly associated with AC histology, stage III-IV, smoking, vascular invasion, tumour spread through air spaces OTP negativity, and TTF-1, Ascl1 and p53 positivity. After adjustment for center and period of diagnosis, both Ki-67 (≥3 versus <3) and histology (AC versus TC) alone significantly added prognostic information to OS and CSS multivariable model with age, stage and OTP; addition of both variables did not provide further prognostic information. Conversely, an improved significance of the DFS prediction model at multivariate analysis was seen by adding Ki-67 (≥3 versus <3, P adj = 0.01) to TC and AC histological distinction, age, lymph node involvement, residual tumour and OTP. Ki-67 ≥ 3% plays a potentially pivotal role in LCT prognosis, irrespective of histological grade.

Grading of Medullary Thyroid Carcinoma: an Interobserver Reproducibility Study

Grade, based on proliferative activity and tumor necrosis, has recently been shown to be prognostic in medullary thyroid carcinoma (MTC) in multivariate analysis. The aim of this study was to evaluate the interobserver reproducibility of assessed grade in MTC. Three groups (each group included one resident/fellow and one attending pathologist) independently evaluated a cohort of 44 sporadic MTC. For each case, all available tumor slides were reviewed, and mitotic count and the presence of tumor necrosis were recorded. Ki-67 was performed, and the Ki-67 proliferative index was determined in the area of highest proliferative activity. Tumors were graded according to the recently published International Medullary Thyroid Carcinoma Grading System (IMTCGS). Kappa statistics were calculated for each individual criterion (mitotic count, Ki-67 proliferative index, and necrosis) and for assigned IMTCGS grade. For our cohort of 44 MTCs, the kappa statistic for mitotic count, Ki-67 proliferative index, and necrosis was 0.68, 0.86, and 0.89, respectively. The kappa statistic for assigned IMTCGS grade was 0.87. Our findings indicate that there was a strong level of agreement for assessment of grade in our cohort of MTC, indicating that grade as assessed by the IMTCGS is not only prognostic but also reproducible.

A Multimodal Biomarker Predicts Dissemination of Bronchial Carcinoid

Background: Curatively treated bronchial carcinoid tumors have a relatively low metastatic potential. Gradation into typical (TC) and atypical carcinoid (AC) is limited in terms of prognostic value, resulting in yearly follow-up of all patients. We examined the additional prognostic value of novel immunohistochemical (IHC) markers to current gradation of carcinoids. Methods: A retrospective single-institution cohort study was performed on 171 patients with pathologically diagnosed bronchial carcinoid (median follow-up: 66 months). The risk of developing distant metastases based on histopathological characteristics (Ki-67, p16, Rb, OTP, CD44, and tumor diameter) was evaluated using multivariate regression analysis and the Kaplan−Meier method. Results: Of 171 patients, seven (4%) had disseminated disease at presentation, and 164 (96%) received curative-intent treatment with either endobronchial treatment (EBT) (n = 61, 36%) or surgery (n = 103, 60%). Among the 164 patients, 13 developed metastases at follow-up of 81 months (IQR 45−162). Univariate analysis showed that Ki-67, mitotic index, OTP, CD44, and tumor diameter were associated with development of distant metastases. Multivariate analysis showed that mitotic count, Ki-67, and OTP were independent risk factors for development of distant metastases. Using a 5% cutoff for Ki-67, Kaplan−Meier analysis showed that the risk of distant metastasis development was significantly associated with the number of risk predictors (AC, Ki-67 ≥ 5%, and loss of OTP or CD44) (p < 0.0001). Six out of seven patients (86%) with all three positive risk factors developed distant metastasis. Conclusions: Mitotic count, proliferation index, and OTP IHC were independent predictors of dissemination at follow-up. In addition to the widely used carcinoid classification, a comprehensive analysis of histopathological variables including Ki-67, OTP, and CD44 could assist in the determination of distant metastasis risks of bronchial carcinoids.

The classification of neuroendocrine neoplasms of the lung and digestive system according to WHO, 5th Edition: similarities, differences, challenges & unmet needs

Neuroendocrine neoplasms (NENs) are a group of disease entities sharing common morphological, ultrastructural and immunophenotypical features, yet with distinct biological behavior and clinical outcome, ranging from benign to frankly malignant. Accordingly, a spectrum of therapeutic options for each single entity is available, including somatostatin analogues (SSA), mTOR-inhibitors, peptide receptor radionuclide therapy (PRRT), non-platinum and platinum chemotherapy. In the last few decades, several attempts have been made in order to (1) better stratify these lesions refining the pathological classifications, so as to obtain an optimal correspondence between the scientific terminology and, the predictive and prognostic features of each disease subtype, and (2) achieve a global Classification encompassing NENs arising at different anatomical sites. Aim of this review is to analyze, compare and discuss the main features and issues of the latest WHO Classifications of NENs of the lung and the digestive system, in order to point out the strengths and limitations of our current understanding of these complex diseases.

Diagnosis of atypical carcinoid can be made on biopsies > 4 mm2 and is accurate

In the 2021 WHO thoracic tumors, gradation of lung carcinoids in biopsies is discouraged. We hypothesized that atypical carcinoid (AC) could be reliably diagnosed in larger preoperative biopsies. Biopsy-resection paired specimens of carcinoid patients were included, and definitive diagnosis was based on the resection specimen according to the WHO 2021 classification. A total of 64 biopsy-resection pairs (26 typical carcinoid (TC) (41%) and 38 AC (59%)) were analyzed. In 35 patients (55%), tumor classification between the biopsy and resection specimen was concordant (26 TC, 9 AC). The discordance in the remaining 29 biopsies (45%, 29 TC, 0 AC) was caused by misclassification of AC as TC. In biopsies measuring < 4 mm², 15/15 AC (100%) were misclassified compared to 14/23 AC (61%) of biopsies ≥ 4 mm². Categorical concordance of Ki-67 in biopsy-resection pairs at threshold of 5% was 68%. Ki-67 in the biopsy was not of additional value to discriminate between TC and AC, irrespective of the biopsy size. Atypical carcinoid is frequently missed in small bronchial biopsies (< 4 mm²). If the carcinoid classification is clinically relevant, a cumulative biopsy size of at least 4 mm² should be considered. Our study provides strong arguments to make the diagnosis of AC in case of sufficient mitosis for AC on a biopsy and keep the diagnosis "carcinoid NOS" for carcinoids with ≤ 1 mitosis per 2 mm². Ki-67 has a good concordance but was not discriminative for definitive diagnosis.

Lung neuroendocrine neoplasms: recent progress and persistent challenges

This review summarizes key recent developments relevant to the pathologic diagnosis of lung neuroendocrine neoplasms, including carcinoids, small cell lung carcinoma (SCLC), and large cell neuroendocrine carcinoma (LCNEC). Covered are recent insights into the biological subtypes within each main tumor type, progress in pathological diagnosis and immunohistochemical markers, and persistent challenging areas. Highlighted topics include highly proliferative carcinoids and their distinction from small cell and large cell neuroendocrine carcinomas (NECs), the evolving role of Ki67, the update on the differential diagnosis of NEC to include thoracic SMARCA4-deficient undifferentiated tumors, the recent data on SCLC transcriptional subtypes with the emergence of POU2F3 as a novel marker for the diagnosis of SCLC with low/negative expression of standard neuroendocrine markers, and the update on the diagnosis of LCNEC, particularly in biopsies. There has been remarkable recent progress in the understanding of the genetic and expression-based profiles within each type of lung neuroendocrine neoplasm, and it is hoped that these insights will enable the development of novel diagnostic, prognostic, and predictive biomarkers to aid in the pathologic assessment of these tumors in the future.

Prognostic nomogram for predicting long-term survival in bronchopulmonary carcinoid tumor patients receiving resection

Background

We analyzed bronchopulmonary carcinoid tumor (BPC) patients receiving resection from the Surveillance, Epidemiology, and End Results (SEER) database to identify the predictive factors of their survival. Then, we developed and validated nomograms to predict overall survival (OS) and cancer-specific survival (CSS) in BPC patients.

Methods

BPC patients registered in the SEER database were included. They were divided into a training set and an internal validation set (7:3). BPC patients from our center were included as an external validation set. Independent prognostic factors identified by a Cox regression model in the training set were used to construct nomograms to predict survival. Discrimination and calibration plots were used to evaluate the predictive accuracy of the nomograms. The nomograms were evaluated in both the internal and the external validation datasets.

Results

Age, pathological type, and N stage were identified as independent prognostic factors of OS and CSS by Cox analyses (all P<0.05). Tumor size ≥2.5 cm (P=0.045) was an independent factor for unfavorable CSS. Based on these variables, nomograms were constructed. All concordance indexes of the training set, internal validation set, and external validation set indicated that the nomograms had the preferable discriminatory ability. The calibration plots for predictions of the 1-, 3-, and 5-year OS and CSS were in excellent agreement.

Conclusions

Age, pathological type, N stage, and tumor size were independent predictive factors of prognosis in BPC patients receiving resection. These nomograms could serve as effective and accurate tools for the prognostic evaluation of patients with BPCs.

Automated Analysis of Proliferating Cells Spatial Organisation Predicts Prognosis in Lung Neuroendocrine Neoplasms

Simple Summary

Lung neuroendocrine neoplasms (lung NENs) are categorised by morphology, defining a classification sometimes unable to reflect ultimate clinical outcome, particularly for the intermediate domains of adenocarcinomas and large-cell neuroendocrine carcinomas. Moreover, subjectivity and poor reproducibility characterise diagnosis and prognosis assessment of all NENs. The aim of this study was to design and evaluate an objective and reproducible approach to the grading of lung NENs, potentially extendable to other NENs, by exploring a completely new perspective of interpreting the well-recognised proliferation marker Ki-67. We designed an automated pipeline to harvest quantitative information from the spatial distribution of Ki-67-positive cells, analysing its heterogeneity in the entire extent of tumour tissue—which currently represents the main weakness of Ki-67—and employed machine learning techniques to predict prognosis based on this information. Demonstrating the efficacy of the proposed framework would hint at a possible path for the future of grading and classification of NENs.

Abstract

Lung neuroendocrine neoplasms (lung NENs) are categorised by morphology, defining a classification sometimes unable to reflect ultimate clinical outcome. Subjectivity and poor reproducibility characterise diagnosis and prognosis assessment of all NENs. Here, we propose a machine learning framework for tumour prognosis assessment based on a quantitative, automated and repeatable evaluation of the spatial distribution of cells immunohistochemically positive for the proliferation marker Ki-67, performed on the entire extent of high-resolution whole slide images. Combining features from the fields of graph theory, fractality analysis, stochastic geometry and information theory, we describe the topology of replicating cells and predict prognosis in a histology-independent way. We demonstrate how our approach outperforms the well-recognised prognostic role of Ki-67 Labelling Index on a multi-centre dataset comprising the most controversial lung NENs. Moreover, we show that our system identifies arrangement patterns in the cells positive for Ki-67 that appear independently of tumour subtyping. Strikingly, the subset of these features whose presence is also independent of the value of the Labelling Index and the density of Ki-67-positive cells prove to be especially relevant in discerning prognostic classes. These findings disclose a possible path for the future of grading and classification of NENs.

Clinical-Pathologic Challenges in the Classification of Pulmonary Neuroendocrine Neoplasms and Targets on the Horizon for Future Clinical Practice

Diagnosing a pulmonary neuroendocrine neoplasm (NEN) may be difficult, challenging clinical decision making. In this review, the following key clinical and pathologic issues and informative molecular markers are being discussed: (1) What is the preferred outcome parameter for curatively resected low-grade NENs (carcinoid), for example, overall survival or recurrence-free interval? (2) Does the WHO classification combined with a Ki-67 proliferation index and molecular markers, such as OTP and CD44, offer improved prognostication in low-grade NENs? (3) What is the value of a typical versus atypical carcinoid diagnosis on a biopsy specimen in local and metastatic disease? Diagnosis is difficult in biopsy specimens and recent observations of an increased mitotic rate in metastatic carcinoid from typical to atypical and high-grade NEN can further complicate diagnosis. (4) What is the (ir)relevance of morphologically separating large cell neuroendocrine carcinoma (LCNEC) SCLC and the value of molecular markers (RB1 gene and pRb protein or transcription factors NEUROD1, ASCL1, POU2F3, or YAP1 [NAPY]) to predict systemic treatment outcome? (5) Are additional diagnostic criteria required to accurately separate LCNEC from NSCLC in biopsy specimens? Neuroendocrine morphology can be absent owing to limited sample size leading to missed LCNEC diagnoses. Evaluation of genomic studies on LCNEC and marker studies have identified that a combination of napsin A and neuroendocrine markers could be helpful. Hence, to improve clinical practice, we should consider to adjust our NEN classification incorporating prognostic and predictive markers applicable on biopsy specimens to inform a treatment outcome-driven classification.

Challenges in Ki-67 assessments in pulmonary large-cell neuroendocrine carcinomas

AIMS

To gather the best available evidence regarding Ki-67% values in large-cell neuroendocrine carcinoma (LCNEC) and determine whether certain cut-off values could serve as a prognostic feature in LCNEC.

METHODS AND RESULTS

Aperio ScanScope AT Turbo, eSlide Manager and ImageScope software (Leica Biosystems) were used to measure Ki-67% in 77 resected LCNEC diagnosed by World Health Organisation (WHO) criteria. Cases were stratified into six classes by 10% Ki-67 increments. Using the Kaplan-Meier method, overall (OS) and disease-free survivals (DFS) were compared by AJCC stage, by six Ki-67% classes and with Ki-67% cut-points ≥20% and ≥40%. Tumours were from 0.9 to 11.5 cm and pathological stages 1-3. The system measured Ki-67% positivity using 4072-44 533 tumour nuclei per case (mean 16610 ± 8039). Ki-67% ranged from 1 to 64% (mean = 26%; median = 26%). Only 16 (21%) tumours had Ki-67% ≥40%. OS ranged from 1 to 298 months (median follow-up = 25 months). DFS ranged from 1 to 276 months (median follow-up = 9 months). OS and DFS differed across AJCC stage (overall log-rank P = 0.038 and P = 0.037). However, neither OS nor DFS significantly correlated with Ki-67% when six or two classes were used with either ≥20% Ki-67 or ≥40% Ki-67 as cut-point. A literature review identified 14 reports meeting our inclusion criteria with ≥10 LCNEC. Reported Ki-67% ranged from 2% to 100%. Problems contributing to variability in Ki-67% measurements are discussed.

CONCLUSION

Our findings caution against a blanket use of 20%, 40% or other Ki-67% cut-points for LCNEC diagnosis or prognostication.

Pulmonary neuroendocrine neoplasms with well differentiated morphology and high proliferative activity: illustrated by a case series and review of the literature

OBJECTIVES

Pulmonary neuroendocrine neoplasms (NENs) are subdivided in carcinoids and neuroendocrine carcinomas (small cell lung carcinoma and large cell neuroendocrine carcinoma (LCNEC)), based on the presence of necrosis and mitotic index (MI). However, it is unclear if tumors with well differentiated morphology but high proliferation rate should be regarded as LCNEC or as high grade carcinoids. In previous case series, a longer overall survival then expected in LCNEC has been suggested. We describe 7 of those cases analyzed for pRb expression and overall survival.

MATERIAL AND METHODS

Cases with well differentiated morphology, but MI > 10/2mm² and/or Ki-67 proliferation index >20% were selected based on pathology reports of consecutive NENs in our university medical center (Maastricht UMC+, 2007-2018) and confirmed by pathological review. Immunohistochemistry was performed to assess pRb expression.

RESULTS

Seven stage IV cases were included in this study. Median overall survival was 8 months (95% confidence interval 5-11 months). Cases with well differentiated morphology and preserved pRb expression (4/7) had a median overall survival of 45 months.

CONCLUSION

A subgroup of pulmonary NENs with well differentiated morphology but high proliferation rate likely exists. pRb staining might be helpful to predict prognosis, but clinical relevance remains to be studied.

Multiple faces of pulmonary large cell neuroendocrine carcinoma: update with a focus on practical approach to diagnosis

Pulmonary large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive malignancy that is strongly linked to smoking and notoriously difficult to diagnose and treat. Recent molecular data reveal that it represents a biologically heterogeneous group of tumors, characterized by morphologic and genomic diversity that straddles small cell and non-small cell lung carcinomas (NSCLCs), and in a minority of cases atypical carcinoids. This review provides an update on recent molecular and clinical developments in LCNEC with the main focus on practical approach to pathologic diagnosis using illustrative examples of the main differential diagnostic considerations.

Ki-67 Labeling Index in Pulmonary Carcinoid Tumors: Comparison Between Small Biopsy and Resection Using Tumor Tracing and Hot Spot Methods

CONTEXT.—

Pulmonary carcinoids are classified as typical or atypical by assessing necrosis and mitoses, which usually cannot be adequately assessed on small biopsies. Ki-67 is not currently used to grade pulmonary carcinoids, but it may be helpful to determine preliminary grade in biopsies. However, the rate at which Ki-67 could underestimate or overestimate grade on small biopsies has not been well studied.

OBJECTIVE.—

To compare Ki-67 labeling obtained on small biopsies to subsequent resection.

DESIGN.—

Ki-67 was performed on paired biopsy and resection specimens from 55 patients. Slides were scanned using Aperio ScanScope. Labeling index was determined using automated hot spot and tumor tracing methods.

RESULTS.—

The study included 41 typical and 14 atypical carcinoids. Atypical carcinoids were larger and had more distant metastases. Death from disease occurred in 3 patients (all had atypical carcinoids). Median hot spot Ki-67 labeling index was greater in resection compared with biopsy by 0.7% (P = .02). Median tumor tracing Ki-67 was lower in resection compared with biopsy by 0.5% (P < .001). Receiver-operating characteristic analysis showed similar hot spot Ki-67 cutoffs to predict atypical histology (3.5% for biopsy, 3.6% for resection; area under the curve [AUC], 0.75 and 0.74, respectively). Different optimal cutoffs were needed for tracing method based on biopsy (2.1%; AUC, 0.75) compared with resection (1.0%; AUC, 0.67).

CONCLUSIONS.—

Hot spot Ki-67 tends to underestimate grade on small biopsies, whereas grade is overestimated by tumor tracing. Hot spot Ki-67 cutoff of 3.5% predicted atypical histology for both biopsy and resection. Different biopsy and resection cutoffs were necessary for tumor tracing, which would make clinical implementation more difficult.

A Semiquantitative Scoring System May Allow Biopsy Diagnosis of Pulmonary Large Cell Neuroendocrine Carcinoma

OBJECTIVES

The aim of this study was to devise reproducible biopsy criteria for distinguishing pulmonary large cell neuroendocrine carcinoma (LCNEC) from non-small cell lung carcinoma (NSCLC).

METHODS

Tissue microarrays of LCNEC and NSCLC were generated from resection specimens and used as biopsy surrogates. They were stained for neuroendocrine markers, Ki-67, napsin-A, and p40, and independently analyzed by standardized morphologic criteria by four pathologists. Tumors were scored based on morphology, neuroendocrine marker expression, and Ki-67 proliferative index.

RESULTS

The average total score for LCNEC was significantly higher than for NSCLC (5.65 vs 0.51, P < .0001). Utilizing a cutoff score of 4 or higher showed 100% sensitivity and 99% specificity for LCNEC diagnosis, with an excellent agreement among four pathologists (98%).

CONCLUSIONS

The proposed semiquantitative approach based on a combination of specific morphologic and immunophenotypic features may be a useful tool for biopsy diagnosis of LCNEC.

Large cell neuroendocrine carcinoma with a solitary brain metastasis and low Ki-67: a unique subtype

INTRODUCTION

Stage IV large cell neuroendocrine carcinoma (LCNEC) of the lung generally presents as disseminated and aggressive disease with a Ki-67 proliferation index (PI) 40-80%. LCNEC can be subdivided in two main subtypes: the first harboring TP53/RB1 mutations (small-cell lung carcinoma (SCLC)-like), the second with mutations in TP53 and STK11/KEAP1 (non-small-cell lung carcinoma (NSCLC)-like). Here we evaluated 11 LCNEC patients with only a solitary brain metastasis and evaluate phenotype, genotype and follow-up.

METHODS

Eleven LCNEC patients with solitary brain metastases were analyzed. Clinical characteristics and survival data were retrieved from medical records. Pathological analysis included histomorphological analysis, immunohistochemistry (pRB and Ki-67 PI) and next-generation sequencing (TP53, RB1, STK11, KEAP1 and MEN1).

RESULTS

All patients had N0 or N1 disease. Median overall survival (OS) was 12 months (95% confidence interval (CI) 5.5-18.5 months). Mean Ki-67 PI was 59% (range 15-100%). In 6/11 LCNEC Ki-67 PI was ≤40%. OS was longer for Ki-67 ≤40% compared to >40% (17 months (95% CI 11-23 months) vs 5 months (95% CI 0.7-9 months), P = 0.007). Two patients were still alive at follow-up after 86 and 103 months, both had Ki-67 ≤40%. 8/11 patients could be subclassified, and both SCLC-like (n = 6) and NSCLC-like (n = 2) subtypes were present. No MEN1 mutation was found.

CONCLUSION

Stage IV LCNEC with a solitary brain metastasis and N0/N1 disease show in the majority of cases Ki-67 PI ≤40% and prolonged survival, distinguishing them from general LCNEC. This unique subgroup can be both of the SCLC-like and NSCLC-like subtype.

[Immunophenotyping of lung tumors : An update]

The WHO Classification of Lung Tumors (2015) established the use of immunohistochemical stainings for resection specimens, however, detailed recommendations had been missing. Now, an international expert panel has summarized key questions for daily routine practice and provided recommendations to assist the community in the appropriate use of immunohistochemistry in this context. This article provides an overview of the most important aspects.

Automated quantification of Ki-67 index associates with pathologic grade of pulmonary neuroendocrine tumors

Background:

Classification of the pulmonary neuroendocrine tumor (pNET) categories is a step-wise process identified by the presence of necrosis and number of mitoses per 2 mm². In neuroendocrine tumor pathology, Ki-67 was first described as a prognostic factor in the pancreas and incorporated into the grading system of digestive tract neuroendocrine neoplasms in the 2010 WHO classification. However, the significance of Ki-67 in pNETs was still a controversial issue. This study was to investigate the potentially diagnostic value of Ki-67 in pNETs.

Methods:

We retrieved 159 surgical specimens of pNETs, including 35 typical carcinoids (TCs), 2 atypical carcinoid (ACs), 28 large-cell neuroendocrine carcinomas (LCNECs), 94 small-cell lung cancers (SCLCs). Manual conventional method (MCM) and computer-assisted image analysis method (CIAM) were used to calculate the Ki-67 proliferative index. In CIAM, 6 equivalent fields (500 × 500 μm) at 10× magnification were manually annotated for digital image analysis.

Results:

The Ki-67 index among the 4 groups with ranges of 0.38% to 12.66% for TC, 4.34% to 29.48% for AC, 30.67% to 93.74% for LCNEC, and 40.71% to 96.87% for SCLC. The cutoff value of Ki-67 index to distinguish low grade with high grade was 30.07%. For the univariate survival analyses in pNETs, both the overall survival and progression-free survival correlated with Ki-67 index. In addition, the Ki-67 index performed by CIAM was proved to be of great positive correlation with MCM.

Conclusions:

Ki-67 index counted by CIAM is a reliable method and can be a useful adjunct to classify the low- and high-grade NETs.

Ki-67 Evaluation for Clinical Decision in Metastatic Lung Carcinoids: A Proof of Concept

Accrual of metastatic pulmonary carcinoid patients for therapy is usually relied on clinical and histologic characterization, with no role for the proliferation activity as defined by Ki-67 labelling index (LI). A total of 14 carcinoid patients with tumour primaries (TP) and 19 corresponding tumour metastases (TM) were blindly reviewed by 2 different pathologists for necrosis, mitotic count, and Ki-67 LI. Ki-67 LI outperformed histologic subtyping, mitotic count, and necrosis with good to almost excellent (0.40-0.75) inter-observer agreement. About 10% cut-off Ki-67 LI predicted survival better than histology for TP and TM for both observers. The TM patients survived differently according to diverse treatments (somatostatin analogues [SSAs], analogues plus additional treatments except for platinum; platinum-based chemotherapy) in close correlation with <10%, 10% to 20%, and >20% cut-off thresholds of Ki-67 LI, respectively. There was also a trend for an increase in Ki-67 LI in TM as compared with TP. This is the first proof of concept in which a clinical potential is preliminarily suggested for Ki-67 LI to better stratify pulmonary metastatic carcinoid patients for treatment according to a criterion of histology-independent biological aggressiveness.

The use of Ki-67 labeling index to grade pulmonary well-differentiated neuroendocrine neoplasms: current best evidence

Although Ki-67 labeling index (Ki-67%) is not a diagnostic or grading criterion in the World Health Organization classification of pulmonary carcinoid tumor, oncologists often request this test. A survey was administered at a North American Society for Neuroendocrine Tumors meeting to understand how Ki-67% is used in oncologic practices. A systematic literature review was performed to gather best evidence regarding the use of Ki-67%. Consecutive pulmonary carcinoids were stratified into pulmonary typical carcinoids with Ki-67% <5% (group A, n = 187), typical carcinoids with Ki-67% ≥5% (group B, n = 38) and atypical carcinoids irrespective of Ki-67% (group C, n = 31). Overall survival, progression-free survival, recurrence proportions and time to recurrence were compared, by group, using the log-rank test, chi-square statistics and ANOVA, respectively. Our survey confirmed that Ki-67% is frequently used by specialists caring for these patients. Ki-67% of 1-7% significantly correlated with overall survival in the literature but we found no information about Ki-67% cut-off values that would accurately distinguish pulmonary typical from atypical carcinoids or estimate the prognosis of patients stratified by World Health Organization diagnosis and Ki-67% cut-off. Overall survival was significantly different in our 3 patient groups (p < 0.001), with survival probabilities decreasing from groups A to C. Progression-free survival was significantly longer in group A than B (p < 0.007). Our results support the concept that by combining World Health Organization diagnosis and Ki-67%, pulmonary carcinoids can be stratified into 3 grades: G1 (typical carcinoids with Ki-67% <5), G2 (typical carcinoids with Ki-67% ≥5%) and G3 (atypical carcinoids) with different prognoses.

Comparative evaluation of three proliferation markers, Ki-67, TOP2A, and RacGAP1, in bronchopulmonary neuroendocrine neoplasms: Issues and prospects

The classification of bronchopulmonary neuroendocrine neoplasms (BP-NEN) into four tumor entities (typical carcinoids (TC), atypical carcinoids (AC), small cell lung cancers (SCLC), large cell neuroendocrine lung carcinomas (LCNEC)) is difficult to perform accurately, but important for prognostic statements and therapeutic management decisions. In this regard, we compared the expression of three proliferation markers, Ki-67, Topoisomerase II alpha (TOP2A), and RacGAP1, in a series of tumor samples from 104 BP-NEN patients (24 TC, 21 AC, 52 SCLC, 7 LCNEC) using different evaluation methods (immunohistochemistry (IHC): Average evaluation, Hotspot evaluation, digital image analysis; RT-qPCR).

The results indicated that all three markers had increased protein and mRNA expression with poorer differentiation and correlated well with each other, as well as with grading, staging, and poor survival. Compared with Ki-67 and TOP2A, RacGAP1 allowed for a clearer prognostic statement. The cut-off limits obtained for Ki-67-Average (IHC) were TC-AC 1.5, AC-SCLC 19, and AC-LCNEC 23.5. The Hotspot evaluation generated equal to higher, the digital image analysis generally lower between-entity cut-off limits.

All three markers enabled a clear-cut differentiation between the BP-NEN entities, and all methods evaluated were suitable for marker assessment. However, to define optimal cut-off limits, the Ki-67 evaluation methods should be standardized. RacGAP1 appeared to be a new marker with great potential.

Orthopedia homeobox is preferentially expressed in typical carcinoids of the lung

BACKGROUND

Twenty-seven percent of neuroendocrine tumors (NETs) are associated with distant metastases, and in some patients, the primary site is unknown. Orthopedia homeobox protein (OTP) has been described as a useful marker for lung carcinoids (LCs) and for separating low-grade typical carcinoids (TCs) from intermediate-grade atypical carcinoids (ACs) in resection specimens. This study evaluated OTP, thyroid transcription factor 1 (TTF-1), and Ki-67 expression in fine-needle aspiration (FNA) samples of various NETs.

METHODS

A search for NETs diagnosed via FNA with subsequent resection was performed. Cell block sections were stained for OTP, TTF-1, and mindbomb E3 ubiquitin protein ligase 1 (Mib-1). Nuclear expression for OTP and TTF-1 was considered positive. Nuclear Ki-67 staining was reported as a percentage. Results were correlated with the grade and primary site for resection specimens.

RESULTS

Sixty-three FNA samples of NETs were identified: 14 liver samples, 14 pancreatic samples, 13 lymph node samples, 12 lung samples, 3 retroperitoneum samples, 2 small intestine samples, and 5 other samples. OTP was positive in 12 of 63 NETs (19%) from the following sites: lung (n = 8), liver (lung primary; n = 2), skin (n = 1), and lymph node (lung primary; n = 1). In well-differentiated NETs, only LCs were OTP-positive, whereas TTF-1 was positive in LCs and nonlung NETs (67% vs 7%). Within the LC category, OTP was positive in 100% of the TCs versus 17% of the ACs.

CONCLUSIONS

OTP is specific for LCs because well-differentiated nonlung NETs are negative for OTP. OTP preferentially stains TCs over ACs. In well-differentiated NETs, OTP staining is highly specific for LCs, and in combination with a low Ki-67 index, it suggests a pulmonary TC. Cancer Cytopathol 2018;126:236-42. © 2018 American Cancer Society.

Analysis of the proliferative activity in lung adenocarcinomas with specific driver mutations

In the last decade it became evident that many lung adenocarcinomas (ADC) harbor key genetic alterations such as KRAS, EGFR or BRAF mutations as well as rearrangements of ROS1 or ALK that drive these tumors. In the present study we investigated whether different driver mutations of ADC result in different proliferation rates, which might have clinical impact, including resistance to therapy, recurrence and prognosis. We analyzed the proliferation index (PI) on full slides of surgically resected ADC (n = 230) with known genetic aberrations by means of immunohistochemistry and subsequent digital image analysis and correlated the results with clinicopathological variables including overall (OS) and disease free survival (DFS). We did not observe significant differences in OS or DFS regarding the KRAS or EGFR mutational status (P = 0.56). However, KRAS mutated ADC showed an increased PI compared to EGFR mutated ADC, and ADC with ALK translocations (P < 0.01). Subgroup analysis of EGFR mutated ADC showed a higher PI for tumors harboring a mutation in exon 18 and 20, compared to tumors with a mutation in exon 19 or 21. A PI of 11.5% was the best possible prognostic stratificator for OS (P = 0.01 in KRAS mutated and P < 0.01 in EGFR mutated ADC). In conclusion, the PI differs significantly among ADC with distinct driver mutations. This might explain the varying indications for a prognostic relevance of the PI observed in prior studies. Our study provides a basis for the establishment of a reliable and clinically meaningful PI threshold.

Lung Carcinoids: Long-Term Surgical Results and the Lack of Prognostic Value of Somatostatin Receptors and Other Novel Immunohistochemical Markers

BACKGROUND/AIMS

Lung carcinoids (LCs) are often diagnosed at an early stage and surgical intervention becomes the next phase of treatment. To date, there is lack of long-term follow-up data after surgery and prognostication based on WHO classification criteria and evolving prognostic markers, particularly the expression of somatostatin receptors (SSR).

METHODS

We included 102 consecutive patients (72 women; age at baseline 51 ± 16 years [mean ± SD]) with LCs, who underwent thoracic surgery (n = 99) and/or laser treatment (n = 8). Hospital charts were reviewed for clinico-pathological parameters. Immunohistochemical (IHC) expression of SSR1-5 and other novel markers were studied with regard to their prognostic value.

RESULTS

Five- and 10-year overall survival (OS) was 96 and 83% respectively; relative survival (RS) was 101 and 93% respectively; and event-free survival (EFS) was 80 and 67% respectively. Independent prognostic factors for OS, RS and/or EFS were age at diagnosis, histopathological type and the presence of ipsilateral mediastinal subcarinal lymph node metastases. Macro-radicality of resective surgery and its extent were associated with increased OS and EFS. The IHC expression of SSR1-5 and other novel markers was not associated with OS or EFS.

CONCLUSION

The long-term outcome of surgically treated patients with LCs is favourable. Age, histopathological type and ipsilateral mediastinal subcarinal lymph node status at baseline were independent prognostic factors for survival and disease recurrence or progression. The extent of surgery and operative macro-radicality also had an impact on prognosis. None of the IHC markers tested appeared to be associated with disease prognosis.

Lung neuroendocrine tumors: pathological characteristics

Lung neuroendocrine tumors (NETs) are a heterogeneous family of neoplasms comprising four histologic types, namely typical and atypical carcinoid (TC and AC), large-cell neuroendocrine and small cell carcinoma (SCC). Classification criteria include the number of mitoses per 2 mm2, the occurrence and extent of necrosis, cytological and histological features and immunohistochemistry for neuroendocrine markers. The classification system and the diagnostic workflow of lung NETs are apparently easy to apply and well established. However, several unresolved issues still exist in classification and pathological characterization of these tumors, probably because inter-observer diagnostic reproducibility remains disappointing, likely due to inconsistency in recognizing necrosis, mitoses and cytological details, especially in small biopsy or cytological materials. Furthermore, the lack of strong prognostic and grading criteria leads to the incomplete interpretation of some rare intermediate entities that stand in between AC and large cell neuroendocrine carcinoma (LCNEC) categories.

Classification of pulmonary neuroendocrine tumors: new insights

Neuroendocrine tumors of the lung (Lu-NETs) embrace a heterogeneous family of neoplasms classified into four histological variants, namely typical carcinoid (TC), atypical carcinoid (AC), large cell neuroendocrine carcinoma (LCNEC) and small cell lung carcinoma (SCLC). Defining criteria on resection specimens include mitotic count in 2 mm2 and the presence or absence of necrosis, alongside a constellation of cytological and histological traits including cell size and shape, nuclear features and overall architecture. Clinically, TC are low-grade malignant tumors, AC intermediate-grade malignant tumors and SCLC/LCNEC high-grade malignant full-blown carcinomas with no significant differences in survival between them. Homologous tumors arise in the thymus that occasionally have some difficulties in differentiating from the lung counterparts when presented with large unresectable or metastatic lesions. Immunohistochemistry (IHC) helps refine NE diagnosis at various anatomical sites, particularly on small-sized tissue material, in which only TC and small cell carcinoma categories can be recognized easily on hematoxylin & eosin stain, while AC and LCNEC can only be suggested on such material. The Ki-67 labeling index effectively separates carcinoids from small cell carcinoma and may prove useful for the clinical management of a metastatic disease to help the therapeutic decision-making process. Although carcinoids and high-grade neuroendocrine carcinomas in the lung and elsewhere make up separate tumor categories on molecular grounds, emerging data supports the concept of secondary high-grade NETs arising in the preexisting carcinoids, whose clinical and biological relevance will have to be placed into the proper context for the optimal management of these patients. In this review, we will discuss the selected, recent literature with a focus on current issues regarding Lu-NET nosology, i.e., classification, derivation and tumor evolution.

Distinctive pathological and clinical features of lung carcinoids with high proliferation index

Typical (TCs) and atypical carcinoids (ACs) are defined based on morphological criteria, and no grading system is currently accepted to further stratify these entities. The 2015 WHO classification restricts the Ki-67 role to biopsy or cytology samples, rather than for prognostic prediction. We aimed to investigate whether values and patterns of Ki-67 alone would allow for a clinically meaningful stratification of lung carcinoids, regardless of histological typing. Ki-67 proliferation index and pattern (homogeneous versus heterogeneous expression) were assessed in a cohort of 171 TCs and 68 ACs. Cases were subdivided into three Ki-67 ranges (<4/4–9/≥10%). Correlations with clinicopathological data, univariate and multivariate survival analyses were performed. The majority of cases (61.5%) belonged to the <4% Ki-67 range; 25.1 and 13.4% had a proliferation index of 4–9% and ≥10%, respectively. The <4% Ki-67 subgroup was significantly enriched for TCs (83%, p < 0.0001); ACs were more frequent in the subgroup showing Ki-67 ≥ 10% (75%, p < 0.0001). A heterogeneous Ki-67 pattern was preferentially seen in carcinoids with a Ki-67 ≥10% (38%, p < 0.02). Mean Ki-67 values ≥4 and ≥10% identified categories of poor prognosis both in terms of disease-free and overall survival (p = 0.003 and <0.0001). At multivariate analysis, the two thresholds did not retain statistical significance; however, a Ki-67 ≥ 10% identified a subgroup of dismal prognosis even within ACs (p = 0.03) at univariate analysis. Here, we describe a subgroup of lung carcinoids showing brisk proliferation activity within the necrosis and/or mitotic count-based categories. These patients were associated with specific clinicopathological characteristics, to some extent regardless of histological subtyping.

Prognostic Significance of CD44 and Orthopedia Homeobox Protein (OTP) Expression in Pulmonary Carcinoid Tumours

CD44 and orthopedia homeobox protein (OTP) expressions have shown to be predictive of overall survival in pulmonary carcinoid (PC) tumours. The scope of the present study was to validate their role in PC patients and investigate potential application in clinical practice. Data was collected from patients presenting to a tertiary cancer centre diagnosed with PC between 2003 and 2015. Diagnosis was confirmed by central pathology review. Formalin-fixed paraffin-embedded (FFPE) tissue samples collected at diagnosis were scored using immunohistochemistry (H score) for standard CD44 and nuclear and cytoplasmic OTP protein expression. The study included 108 patients. High CD44/nuclear OTP (nOTP) expression was strongly associated with typical carcinoid (TC) histology (p < 0.001). Eighty-six patients, who underwent radical surgical resection, were selected to assess the impact of patient and tumour parameters on relapse-free survival (RFS). Sixty-nine (80 %) had TC and 17 (20 %) had atypical carcinoid tumours. On multivariate analysis, high CD44 and nOTP expression, TC histology and non-infiltrative tumour growth were associated with superior RFS. Early stage TC (stage pT1aN0) patients (N = 32; 46 %) had excellent prognosis irrespective of CD44/nOTP status. Importantly, TC patients with locally advanced disease (defined as >pT1aN0) and high CD44/nOTP expression (N = 26; 38 %) had excellent RFS (p = 0.005) compared to those with the same stage but low CD44 and/or nOTP (N = 11; 16 %). Additionally, the combination of CD44/nOTP expression and tumour growth pattern led to a more accurate prognostic system compared to the established WHO classification of PC tumours (concordance index = 0.902 vs 0.811, respectively, p < 0.001). Assessment of CD44/nOTP expression combined with tumour growth pattern identifies clear groups with largely different prognosis. These findings provide important information on how patients with these resected cancers should be followed up.

Ki-67 labeling index of neuroendocrine tumors of the lung has a high level of correspondence between biopsy samples and surgical specimens when strict counting guidelines are applied

Optimal histopathological analysis of biopsies from metastases of neuroendocrine tumor (NET) of the lung requires more than morphology only. Additional parameters such as Ki-67 labeling index are required for adequate diagnosis, but few studies have compared reproducibility of different counting protocols and modalities of reporting on biopsies of lung NET. We compared the results of four different manual counting techniques to establish Ki-67 LI. On 47 paired biopsies and surgical specimens from 22 typical carcinoids (TCs), 14 atypical carcinoids (ACs), six large cell neuroendocrine carcinomas (LCNECs), and five small cell carcinomas (SCCs) immunohistochemical staining of Ki-67 antigen was performed. We counted, in regions of highest nuclear staining (HSR), a full ×40-high-power field (diameter = 0.55 mm), 500 or 2000 cells, or 2 mm² surface area, including the HSR or the entire biopsy fragment(s). Mitoses and necrosis were evaluated in an area of 2 mm² or the entire biopsy fragment(s). Between the four counting methods, no differences in Ki-67 LI were observed. However, a Ki-67 LI higher than 5% was found in only four cases when in an HSR, 500 cells were counted (18%), five (23%) when in an HSR 2000 cells were counted, four (18%) when 2 mm² were counted, and one (5%) TC case when the entire biopsy was counted. A 20% cutoff distinguished TC and AC from LCNEC and SCC with 100% specificity and sensitivity, while mitoses and necrosis failed to a large extent. Ki-67 LI in biopsy samples was concordant with that in resection specimens when 2000 cells, 2 mm², or the entire biopsy fragment(s) were counted. Our results are important for clinical management of patients with metastases of a lung NET.

[Diagnosis, prognosis, and prediction of non-small cell lung cancer. Importance of morphology, immunohistochemistry and molecular pathology]

Tumor diagnostics are based on histomorphology, immunohistochemistry and molecular pathological analysis of mutations, translocations and amplifications which are of diagnostic, prognostic and/or predictive value. In recent decades only histomorphology was used to classify lung cancer as either small (SCLC) or non-small cell lung cancer (NSCLC), although NSCLC was further subdivided in different entities; however, as no specific therapy options were available classification of specific subtypes was not clinically meaningful. This fundamentally changed with the discovery of specific molecular alterations in adenocarcinoma (ADC), e.g. mutations in KRAS, EGFR and BRAF or translocations of the ALK and ROS1 gene loci, which now form the basis of targeted therapies and have led to a significantly improved patient outcome. The diagnostic, prognostic and predictive value of imaging, morphological, immunohistochemical and molecular characteristics as well as their interaction were systematically assessed in a large cohort with available clinical data including patient survival. Specific and sensitive diagnostic markers and marker panels were defined and diagnostic test algorithms for predictive biomarker assessment were optimized. It was demonstrated that the semi-quantitative assessment of ADC growth patterns is a stage-independent predictor of survival and is reproducibly applicable in the routine setting. Specific histomorphological characteristics correlated with computed tomography (CT) imaging features and thus allowed an improved interdisciplinary classification, especially in the preoperative or palliative setting. Moreover, specific molecular characteristics, for example BRAF mutations and the proliferation index (Ki-67) were identified as clinically relevant prognosticators. Comprehensive clinical, morphological, immunohistochemical and molecular assessment of NSCLCs allow an optimized patient stratification. Respective algorithms now form the backbone of the 2015 lung cancer World Health Organization (WHO) classification.

Limited additive value of the Ki-67 proliferative index on patient survival in World Health Organization-classified pulmonary carcinoids

AIMS

Currently pulmonary carcinoids are separated into typical and atypical based on mitotic count and presence of necrosis, according to the World Health Organization. At variance with gastroenteropancreatic neuroendocrine tumours, which are graded based on mitotic count and Ki-67 proliferative index, the use of Ki-67 for grading pulmonary carcinoids is still under debate.

METHODS AND RESULTS

In this study we evaluated the prognostic impact of Ki-67 assessment in a multicentre cohort of 201 carcinoids [147 typical carcinoids (TCs) and 54 atypical carcinoids (ACs)] using manual analysis (2000 cells counted) and digital image analysis (in-house Leica Qwin program; ≥4500 cells counted). The Ki-67 proliferative index was correlated with overall survival by means of univariate analysis and in comparison to clinical data by means of multivariable analysis. The Ki-67 index was significantly higher in ACs than in TCs for both counting methods (P ≤ 2.7e^-5 ). In addition, using cut-offs of 2.5% and 4% (manual counting) or 1% and 5% (digital analysis), the highest differences in overall survival were observed (P ≤ 0.0067). Nevertheless, histopathological classification into TCs and ACs showed an equally strong association with disease outcome, although Ki-67 had some additive value within TCs. Ki-67 index was not an independent predictor of survival in multivariable analysis.

CONCLUSIONS

Our study demonstrates that, although Ki-67 is a strong prognostic factor for pulmonary carcinoids, its usefulness in addition to histopathology in prediction of prognosis is limited. None the less, it may have additional value, especially in cases that are difficult to classify, in combination with histopathology and other molecular markers.

Evaluation of diagnostic and prognostic significance of Ki-67 index in pulmonary carcinoid tumours

BACKGROUND

Pulmonary carcinoid (PC) tumours are classified as either typical (TC) or atypical (AC) according to mitotic index (MI) and presence of necrosis. The aim of this study was to analyse the diagnostic and prognostic values of the Ki-67 index in PC.

METHODS/PATIENTS

Between January 2001 and March 2015, we evaluated 94 consecutive patients with a confirmed diagnosis of TC (n = 75) or AC (n = 19) at our institution. Diagnostic histology was centrally reviewed by a local expert neuroendocrine pathologist, with assessment of Ki-67, MI, and necrosis.

RESULTS

Median patient follow-up was 35 months. Eighty-four patients who underwent curative surgical resection were included in the survival analysis for identification of prognostic factors. Ki-67 index showed high diagnostic accuracy to predict histological subtype when assessed by receiver operator characteristic curves with an area under the curve of 0.923 (95% CI 0.852-0.995, p < 0.001). Multivariate analysis showed that MI, Ki-67 index, and the presence or absence of necrosis were independent prognostic factors for relapse-free survival. Combination of MI, Ki-67, and necrosis led to the classification of patients into four different prognostic groups (very low, low, intermediate, and high risks of relapse).

CONCLUSIONS

The current study proposes the incorporation of Ki-67 index in the prognostic classification of PC tumours. Due to the limited number of patients and length of follow-up, the current model needs validation by larger cohort studies. Nevertheless, our results suggest that Ki-67 index and MI have continuous effect on prognosis. Prognostic models incorporating multiple cutoffs of Ki-67 and MI might better predict outcome and inform clinical decisions.

Diagnosis and management of gastrointestinal neuroendocrine tumors: An evidence-based Canadian consensus

The majority of neuroendocrine tumors originate in the digestive system and incidence is increasing within Canada and globally. Due to rapidly evolving evidence related to diagnosis and clinical management, updated guidance on the diagnosis and treatment of gastrointestinal neuroendocrine tumors (GI-NETs) are of clinical importance. Well-differentiated GI-NETs may exhibit indolent clinical behavior and are often metastatic at diagnosis. Some NET patients will develop secretory disease requiring symptom control to optimize quality of life and clinical outcomes. Optimal management of GI-NETs is in a multidisciplinary environment and is multimodal, requiring collaboration between medical, surgical, imaging and pathology specialties. Clinical application of advances in pathological classification and diagnostic technologies, along with evolving surgical, radiotherapeutic and medical therapies are critical to the advancement of patient care. We performed a systematic literature search to update our last set of published guidelines (2010) and identified new level 1 evidence for novel therapies, including telotristat etiprate (TELESTAR), lanreotide (CLARINET), everolimus (RADIANT-2; RADIANT-4) and peptide receptor radionuclide therapy (PRRT; NETTER-1). Integrating these data with the clinical knowledge of 16 multi-disciplinary experts, we devised consensus recommendations to guide state of the art clinical management of GI-NETs.

[Pulmonary neuroendocrine tumors in the new WHO 2015 classification: Start of breaking new grounds?]

CLASSIFICATION

In the recently published 4th edition of the World Health Organization (WHO) classification of tumors of the lungs, pleura, thymus and heart, all neuroendocrine tumors of the lungs (pNET) are presented for the first time in one single chapter following adenocarcinoma and squamous cell carcinoma and before large cell carcinoma. In this classification, high grade small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC) are differentiated from intermediate grade atypical carcinoids (AC) and low grade typical carcinoids as well as from preinvasive lesions (DIPNECH). In the 3rd WHO classification from 2004, which dealt with resection specimens, SCLC and carcinoids each had a separate chapter and LCNEC was previously listed in the chapter on large cell carcinoma of the lungs. The new WHO classification is for the first time also applicable to lung biopsies.

DIAGNOSTICS

Normally, common features of all pNET are a neuroendocrine morphology (as far as detectable in small biopsies) and expression of the neuroendocrine (NE) markers (chromogranin A, synaptophysin and CD56/NCAM). An immunohistochemical positive staining of at least one NE marker was already recommended in the 3rd edition of the WHO classification (2004) only for LCNEC. Differentiating features are a small or large cell cytomorphology/histomorphology, nuclear criteria and the mitotic rate (for SCLC >10 with a median of 80, for LCNEC >10 median 70, for AC 2 - 10, for TC < 2 each per 2 mm(2)). Tumor cell necrosis usually occurs in SCLC and LCNEC, partially in AC and not in TC. The guideline Ki67 proliferation rates are given for the first time in the new WHO classification for SCLC as 50-100 %, for LCNEC 40-80 %, for AC up to 20 % and for TC up to 5 %.

MOLECULAR PATHOLOGY

Molecular alterations occur in SCLC and LCNEC in large numbers and are very variable in quality. In AC and TC they occur much less frequently and are relatively similar.

CONCLUSION

The direct comparison of all pNET in one chapter facilitates the differential diagnostics of these tumors, provides a better transparency especially of LCNEC and allows a further comprehensive development of the clinical practical and scientific evaluation of pNET. Although a separate terminology of pNET is maintained for the lungs, a careful approach towards the gastroentero-pancreatic NET (gepNET) can be observed.

[Metastatic bronchial carcinoid tumors]

Bronchial carcinoids are uncommon pulmonary neoplasms and represent 1 to 2 % of all lung tumors. In early stage of disease, the mainstay and only curative treatment is surgery. Bronchial carcinoids are generally regarded as low-grade carcinomas and metastatic dissemination is unusual. The management of the metastatic stage is not currently standardized due to a lack of relevant studies. As bronchial carcinoids and in particular their metastatic forms are rare, we apply treatment strategies that have been evaluated in gastrointestinal and pancreatic neuroendocrine tumors. However, bronchial carcinoids have their own characteristic. A specific therapeutic feature of these metastatic tumors is that they require a dual approach: both anti-secretory for the carcinoid syndrome, and anti-tumoral.

Usefulness of Ki-67, Mitoses, and Tumor Size for Predicting Metastasis in Carcinoid Tumors of the Lung: A Study of 48 Cases at a Tertiary Care Centre in Canada

Background. Evaluation of Ki-67 index in lung carcinoid tumors (LCTs) has been of interest in order to identify high risk subsets. Our objectives are (1) to evaluate the usefulness of Ki-67 index, mitoses, and tumor size in predicting metastasis and (2) to compare the Manual Conventional Method (MCM) and the Computer Assisted Image Analysis Method (CIAM) for Ki-67 calculation. Methods. We studied 48 patients with LCTs from two academic centres in Canada. For Ki-67 calculation, digital images of 5000 cells were counted using an image processing software and 2000 cells by MCM. Mitoses/10 HPF was counted. Results. We had 37 typical carcinoids (TCs) and 11 atypical carcinoids (ACs). 7/48 patients developed metastasis. There was a positive relationship between metastasis and carcinoid type (P = 0.039) and metastasis and mitoses (≥2) (P = 0.017). Although not statistically significant, the mean Ki-67 index for ACs was higher than for TCs (0.95% versus 0.72%, CIAM, P = 0.299). Similarly, although not statistically significant, the mean Ki-67 index for metastatic group (MG) was higher than for nonmetastatic group (NMG) (1.01% versus 0.71% by CIAM, P = 0.281). However when Ki-67 index data was categorized at various levels, there is suggestion of a useful cutoff (≥0.50%) to predict metastasis (P = 0.106, CIAM). A significantly higher proportion of patients with mitosis ≥2 and Ki-67 index ≥0.50% had metastasis (P = 0.033) compared to other patients. Similarly patients with tumor size ≥3 cm and Ki-67 ≥0.50% had a greater percentage of metastases than others (P = 0.039). Although there was a strong correlation between two (MCM versus CIAM) counting methods (r = 0.929, P = 0.001), overall the calculated Ki-67 index was slightly higher by MCM (range 0 to 6.4, mean 1.5) compared to CIAM (range 0 to 2.9, mean 0.75). Conclusion. This study confirms that mitoses ≥2 is a powerful predictor of metastasis in LCTs. Although this is a small sample size, there is suggestion that analysis of Ki-67 index along with mitoses and tumor size may be a useful adjunct for predicting metastasis in LCTs.

Nuclear grade plus proliferation grading system for invasive ductal carcinoma of the breast: validation in a tertiary referral hospital cohort

OBJECTIVES

For patients with invasive breast cancer, management decisions are informed by tumor grade according to the Nottingham Grading System (NGS), either on its own or as part of the Nottingham Prognostic Index (NPI). A system retaining the nuclear grade element but substituting the two subjective components, mitosis count and tubule formation, of the NGS with a proliferation index based on Ki-67 (MIB-1) has been proposed (nuclear grade plus proliferation [N+P] grading).

METHODS

We validated the prognostic value of this grading system on a population of 322 women.

RESULTS

N+P grading resulted in more grade I tumors (47.9% vs 4.5%) and fewer grade II (32% vs 51.5%) and grade III (20.1% vs 44%) tumors compared with NGS. The NPI calculated based on N+P grade had a similar association with survival (P < .001; odds ratio, 1.729) as the NPI calculated on the basis of the NGS grade (P < .001; odds ratio, 1.668).

CONCLUSIONS

The N+P system seems equivalent to the NGS system.

Classification of lung neuroendocrine tumors: lights and shadows

Neuroendocrine tumors of the lung are classified into low-grade typical and intermediate-grade atypical carcinoids, and high-grade poorly differentiated neuroendocrine carcinomas of the large and small cell types. This scheme is strongly predictive of patients' prognosis but relies on few and scarcely reproducible pathological parameters (namely mitotic count and assessment of the presence of necrosis), which have been demonstrated to affect the inter-observer agreement of the classification. Moreover, tumor and nodal staging schemes are not specific for lung carcinoids, at variance with neuroendocrine tumors of the gastro-entero-pancreatic system, despite these tumors have specific features that strongly differ from conventional lung cancer. Finally, there is no grading for lung neuroendocrine neoplasms and prognostication, as well as the definition of treatment modalities and clinical strategies, which are based on tumor histotypes, only. However, literature data indicate that the evaluation of Ki-67 proliferation index may be a reliable and useful tool to determine the biological and clinical behavior of neuroendocrine tumors, with special reference to carcinoids, both in pre-operative and surgical samples.

What clinicians are asking pathologists when dealing with lung neuroendocrine neoplasms?

Lung neuroendocrine tumors (NET) are currently classified in resection specimens according to four histological categories, namely typical carcinoid (TC), atypical carcinoid (AC), large-cell neuroendocrine carcinoma (LCNEC) and small cell carcinoma (SCC). Diagnostic criteria have remained unchanged in the 2015 WHO classification, which has ratified the wide acceptance and popularity of such terminology in the pathologists׳ and clinicians׳ community. A unifying umbrella of NE morphology and differentiation has been recognized in lung NET, which has pushed to enter an unique box of invasive tumors along with diffuse idiopathic pulmonary NE cell hyperplasia (DIPNECH) as a pre-invasive lesion with a potential toward the development of carcinoids. However, uncertainties remain in the terminology of lung NET upon small samples, where Ki-67 antigen could play some role to avoid misdiagnosing carcinoids as high-grade NE tumors. Epidemiologic, clinical and genetic traits support a biological three-tier over a pathology four-tier model, according to which TC are low malignancy tumors, AC intermediate malignancy tumors and LCNEC/SCC high malignancy tumors with no significant differences in survival among them. Inconsistencies in diagnostic reproducibility, troubles in the therapy of AC and LCNEC, and limitations to histology within the same tumor category argue in favor of a global re-thinking of lung NET where a grading system could play a role. This review outlines three main key questions in the field of lung NET: (A) unbiased diagnoses, (B) the role of Ki-67 and tumor grading, and (C) management of predictive markers. Answers are still inconclusive, thus additional research is required to improve our understanding on lung NET.

[Neuroendocrine tumors of the lungs. From small cell lung carcinoma to diffuse idiopathic pulmonary neuroendocrine cell hyperplasia]

The new World Health Organization (WHO) classification announced for 2015 will for the first time present all neuroendocrine tumors (NET) of the lungs in one single section. In this classification high grade small cell lung carcinoma (SCLC) and large cell neuroendocrine carcinoma (LCNEC) will be discriminated from intermediate grade atypical carcinoid (AC) and low grade typical carcinoid as well as from the preinvasive lesion diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH). The LCNEC was previously listed under the section of large cell carcinomas. The LCNEC could previously be diagnosed according to the current WHO classification from 2004 which is designed for resection specimens. According to this the main diagnostic criteria are a neuroendocrine growth pattern which can be difficult or impossible to detect in biopsy material, non-small cell cytological features, more than 10 mitoses per 2 mm(2) (mean 70-80 per 2 mm(2)), tumor cell necrosis, and an immunohistochemical positivity for at least one neuroendocrine marker other than neuron-specific enolase (NSE). The presentation of all neuroendocrine tumors of the lungs in one section allows a more direct comparison and a better differential diagnostic discrimination of the different entities.

Diagnosis and treatment of bronchopulmonary neuroendocrine tumours: State of the art

Bronchopulmonary neuroendocrine tumours (BP-NET) are a heterogeneous population of neoplasms with different pathology, clinical behaviour and prognosis compared to the more common lung cancers. The management of BP-NET patients is largely based on studies with a low level of evidence and extrapolation of data obtained from more common types of neuroendocrine tumours. This review reflects our view of the current state of the art of diagnosis and treatment of patients with BP-NET.

Pulmonary neuroendocrine (carcinoid) tumors: European Neuroendocrine Tumor Society expert consensus and recommendations for best practice for typical and atypical pulmonary carcinoids

BACKGROUND

Pulmonary carcinoids (PCs) are rare tumors. As there is a paucity of randomized studies, this expert consensus document represents an initiative by the European Neuroendocrine Tumor Society to provide guidance on their management.

PATIENTS AND METHODS

Bibliographical searches were carried out in PubMed for the terms 'pulmonary neuroendocrine tumors', 'bronchial neuroendocrine tumors', 'bronchial carcinoid tumors', 'pulmonary carcinoid', 'pulmonary typical/atypical carcinoid', and 'pulmonary carcinoid and diagnosis/treatment/epidemiology/prognosis'. A systematic review of the relevant literature was carried out, followed by expert review.

RESULTS

PCs are well-differentiated neuroendocrine tumors and include low- and intermediate-grade malignant tumors, i.e. typical (TC) and atypical carcinoid (AC), respectively. Contrast CT scan is the diagnostic gold standard for PCs, but pathology examination is mandatory for their correct classification. Somatostatin receptor imaging may visualize nearly 80% of the primary tumors and is most sensitive for metastatic disease. Plasma chromogranin A can be increased in PCs. Surgery is the treatment of choice for PCs with the aim of removing the tumor and preserving as much lung tissue as possible. Resection of metastases should be considered whenever possible with curative intent. Somatostatin analogs are the first-line treatment of carcinoid syndrome and may be considered as first-line systemic antiproliferative treatment in unresectable PCs, particularly of low-grade TC and AC. Locoregional or radiotargeted therapies should be considered for metastatic disease. Systemic chemotherapy is used for progressive PCs, although cytotoxic regimens have demonstrated limited effects with etoposide and platinum combination the most commonly used, however, temozolomide has shown most clinical benefit.

CONCLUSIONS

PCs are complex tumors which require a multidisciplinary approach and long-term follow-up.

[Gastroenteropancreatic neuroendocrine neoplasms. Role of biopsies]

Neuroendocrine neoplasms of the pancreas and the gastrointestinal tract are heterogeneous regarding etiology (e.g. sporadic or hereditary), histomorphology, hormone expression, hormone-related functional activity and especially the malignant potential. In neuroendocrine neoplasms the biopsy-based diagnosis plays an important role for the clinical management of patients. The diagnosis most importantly relies on the differentiation (e.g. organoid versus diffuse growth patterns) and the grading of tumors. The latter is based on the proliferation activity as determined by Ki-67 immunostaining and mitotic count and results in the current tumor classification into neuroendocrine tumors G1, neuroendocrine tumors G2 or neuroendocrine carcinomas G3. Occasionally, tumors may show mixed differentiation containing a non-neuroendocrine cancer component. The neuroendocrine markers synaptophysin and chromogranin A are recommended for the immunohistochemical confirmation of the diagnosis. Furthermore, biopsy material can be used to investigate the expression of therapy-related markers, such as somatostatin receptor-2A. Moreover, if needed, the expression of transcription factors and hormones can be determined to obtain information on the possible site of origin of metastatic neuroendocrine neoplasms or to determine the syndrome-inducing hormone in functionally active neuroendocrine neoplasms. Finally, using the stomach as an example, biopsies may also be successfully used to investigate neuroendocrine precursor lesions which may harbor prognostic significance.