Endometrial Mesonephric-Like Carcinoma With Prominent Clear Cell Carcinoma-Like Features

Area of Science:

• Gynecologic Pathology
• Oncologic Pathology
• Molecular Pathology

Background:

• Mesonephric-like adenocarcinoma (MLA) can present with varied morphology.
• Distinguishing pure MLA from mixed tumors with clear cell carcinoma (CCC)-like features is clinically important.

Purpose of the Study:

• To investigate whether prominent clear cell carcinoma (CCC)-like areas within an endometrial mesonephric-like adenocarcinoma (MLA) represent a mixed tumor or a morphologic variant of MLA.
• To analyze the morphologic, immunohistochemical, and molecular features of these distinct areas.

Main Methods:

• Morphologic assessment of tumor components.
• Immunohistochemical staining for key markers (ER, PR, SOX17, calretinin, GATA3, TTF1, CD10, Napsin-A).
• Next-generation sequencing (NGS) for molecular analysis of KRAS variant.

Main Results:

• Approximately 40% of the MLA exhibited CCC-like morphology.
• Both MLA and CCC-like areas showed similar nuclear features and immunoreactivity for ER, PR, SOX17, calretinin, GATA3, and TTF1.
• Diffuse CD10 and Napsin-A expression was confined to the CCC-like areas.
• NGS revealed the same KRAS G12V variant in both components with similar allelic frequencies.

Conclusions:

• The CCC-like areas are interpreted as morphologic mimicry of CCC by MLA, not a distinct component.
• Shared KRAS G12V mutation, similar nuclear features, and specific immunohistochemical profiles support this interpretation.
• This case highlights the potential for MLA to mimic CCC, emphasizing the need for comprehensive analysis to avoid misclassification.