Objective:

To describe a rare case of SMARCB1-deficient malignant melanocytic choroidal tumor with confirmed vertebral metastases and to expand the understanding of the clinicopathologic spectrum of these tumors.

Approach:

• Case Presentation: A 21-year-old woman with progressive left retro-orbital pain and visual impairment underwent enucleation of the left eye, revealing a malignant neoplasm with SMARCB1 deficiency.
• Pathological Examination: Histopathological analysis showed a highly cellular malignant epithelioid neoplasm with rhabdoid features and loss of INI1 expression.
• Molecular Analysis: Molecular testing identified a pathogenic truncating alteration in the SMARCB1 gene, confirming the diagnosis.
• Treatment and Outcome: The patient received palliative radiotherapy and chemotherapy but experienced progressive disease and died three years post-diagnosis.

Key Findings:

• The tumor exhibited loss of INI1 expression and a pathogenic SMARCB1 alteration, c.656C>G, p.(Ser219*).
• Histopathological features included marked cytologic atypia and rhabdoid morphology.
• The case highlights the diagnostic complexity of SMARCB1-deficient tumors with melanocytic differentiation.

Interpretation:

Integrated histopathologic, immunophenotypic, and molecular assessment is crucial to avoid diagnostic misclassification, particularly in unusual intraocular presentations.

Limitations:

• Limited remaining material restricted additional immunostaining.
• The rarity of SMARCB1-deficient tumors complicates comprehensive understanding of their clinicopathologic features.

Conclusion:

This case contributes to the understanding of SMARCB1-deficient tumors and emphasizes the diagnostic complexity associated with these neoplasms.