Interobserver variability for the WHO classification of pulmonary carcinoids

Area of Science:

• Pulmonary pathology
• Oncology
• Histopathology

Background:

• Pulmonary carcinoids are neuroendocrine tumors subclassified into typical (TC) and atypical (AC) based on histopathology.
• Existing classification methods have limitations, including potential misinterpretation of apoptosis as mitotic figures and variable prognostic prediction, particularly for ACs.

Purpose of the Study:

• To assess interobserver variation in the histopathologic classification of pulmonary carcinoids among experienced pathologists.
• To evaluate the impact of histopathologic classification and additional immunomarkers on prognosis.

Main Methods:

• Review of 123 pulmonary carcinoid cases by 5 experienced pulmonary pathologists.
• Classification into unanimous, consensus, and disagreement groups.
• Calculation of κ-values to measure interobserver agreement.
• Correlation of classification results with clinical follow-up and molecular data, including Ki-67 and orthopedia homeobox immunostaining.

Main Results:

• Fair interobserver agreement (κ=0.32) was observed for pulmonary carcinoids.
• Atypical carcinoids (ACs) were significantly more prone to classification disagreements.
• Histopathologic classification alone did not correlate with prognosis.
• Incorporating Ki-67 or orthopedia homeobox immunostaining in disagreement cases significantly improved prognostic correlation.

Conclusions:

• Considerable interobserver variation exists in the histopathologic classification of lung carcinoids, particularly for ACs.
• Additional immunomarkers, such as Ki-67 and orthopedia homeobox, are valuable tools to enhance classification accuracy and prognostic prediction for pulmonary carcinoids.