Second-Generation Neuroendocrine Immunohistochemical Markers: Reflections from Clinical Implementation.

Area of Science:

• Endocrinology
• Oncology
• Histopathology

Background:

• Traditional neuroendocrine tumor diagnosis relies on Chromogranin A (CGA) and Synaptophysin (SYP), which can have limitations.
• These markers may show tissue-specific patterns or focal expression in non-neuroendocrine tumors.
• CGA and SYP can be absent in highly proliferative neuroendocrine carcinomas, complicating diagnosis of metastatic lesions.

Purpose of the Study:

• To discuss the clinical utility of second-generation neuroendocrine markers.
• To highlight advances in identifying neuroendocrine differentiation.
• To present initial clinical experiences with new markers in a tertiary neuroendocrine center.

Main Methods:

• Review of recent advances in neuroendocrine marker development.
• Analysis of immunohistochemical expression patterns of novel markers.
• Clinical case review from a specialized neuroendocrine tumor center.

Main Results:

• Second-generation markers, including ISL LIM Homeobox 1 (ISL1), INSM Transcriptional Repressor 1 (INSM1), and Secretagogin (SECG), offer expanded diagnostic capabilities.
• These new markers often retain expression in poorly differentiated neuroendocrine carcinomas where traditional markers may fail.
• ISL1, INSM1, and SECG demonstrate high specificity, with rare expression in non-neuroendocrine tumors.

Conclusions:

• ISL1, INSM1, and SECG represent significant advancements in the histopathological diagnosis of neuroendocrine tumors.
• Their specificity and reliability, particularly in challenging cases like poorly differentiated carcinomas, enhance diagnostic accuracy.
• These markers are valuable additions to the pathologist's toolkit for improved patient care in neuroendocrine oncology.