Head-to-head: Should Ki67 proliferation index be included in the formal classification of pulmonary neuroendocrine...

Area of Science:

• Pathology
• Oncology
• Pulmonology

Background:

• The 2021 World Health Organization (WHO) classification for lung neuroendocrine neoplasms (NENs) relies on mitotic count, necrosis, and immunohistochemistry.
• Lung NENs are categorized into low- to intermediate-grade neuroendocrine tumors (NETs) and high-grade neuroendocrine carcinomas (NECs).
• Provisional categories like "NET not otherwise specified" (NOS) are used for limited diagnostic material.

Purpose of the Study:

• To discuss the arguments for and against incorporating the Ki-67 proliferation index into the classification and clinical practice of lung NENs.
• To evaluate the utility of Ki-67 in distinguishing between NETs and high-grade NECs.
• To address the ongoing debate surrounding the wider use of Ki-67 in lung NEN diagnosis.

Main Methods:

• Review of current WHO classification criteria for lung NENs.
• Analysis of the role of Ki-67 as a proliferation marker.
• Discussion of existing literature and clinical practices regarding Ki-67 in NENs.

Main Results:

• Ki-67 is a desirable, though non-essential, criterion in the WHO classification for distinguishing NETs from NECs.
• It aids in identifying a provisional category of NETs with elevated mitotic counts and/or Ki-67 index (≥30%).
• The broader application of Ki-67 in lung NENs remains a subject of extensive reporting and debate.

Conclusions:

• The Ki-67 antigen is a valuable marker for assessing proliferation in lung neuroendocrine neoplasms.
• Its definitive role in classification and clinical management requires further consensus and standardization.
• Continued discussion is necessary to optimize the use of Ki-67 in lung NEN diagnosis and patient care.