A Nonchordomatous-looking Chordoma: When INI-1 and Radiology Came to the Rescue!!!

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• SMARCB1/integrase interactor (INI)-1 is a tumor suppressor and core subunit of the ATP-dependent SWI/SNF chromatin remodeling complex.
• INI-1 loss is a valuable diagnostic marker in histopathology, detectable via immunohistochemistry.
• Chordoma is a rare bone tumor typically found in the sacrococcygeal spine of adults, characterized by nuclear brachyury expression.

Observation:

• Poorly differentiated chordoma is a distinct entity, often occurring in children, with a predilection for the skull base.
• This subtype exhibits nuclear brachyury positivity and loss of INI-1 expression.
• The study presents a case of poorly differentiated chordoma in a 5-year-old girl with unusual histomorphologic and immunohistochemical findings.

Findings:

• The case highlights the diagnostic utility of INI-1 loss in identifying poorly differentiated chordoma, particularly in pediatric patients.
• Brachyury positivity combined with INI-1 loss aids in differentiating this aggressive subtype.
• Unusual histomorphologic features were observed in this pediatric case, expanding the known spectrum of the disease.

Implications:

• INI-1 immunohistochemistry is crucial for accurate diagnosis of poorly differentiated chordoma, especially in pediatric oncology.
• Understanding the distinct features of this subtype can improve diagnostic accuracy and guide treatment strategies.
• This case contributes to the literature on rare pediatric malignancies and the role of SWI/SNF complex alterations in tumorigenesis.