An unusual breast mass: primary synovial sarcoma

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Breast lesions require accurate diagnosis for appropriate management.
• Distinguishing benign from malignant breast tumors can be complex, especially with rare entities.
• Synovial sarcoma is a rare soft tissue sarcoma typically affecting extremities, rarely presenting in the breast.

Observation:

• A 54-year-old woman presented with mastalgia and a 6 mm breast lesion identified on imaging.
• Core biopsy revealed a lesion with predominant epithelioid and minor spindle cell components.
• Initial differential diagnoses included intraduct papilloma/adenoma and adenomyoepithelioma.

Findings:

• Immunohistochemistry initially did not support common breast lesion diagnoses.
• Further immunohistochemistry suggested the possibility of synovial sarcoma.
• Fluorescence in-situ hybridization confirmed the diagnosis by identifying the characteristic t(x;18)(p11.2;q11.2) translocation.

Implications:

• Accurate diagnosis of synovial sarcoma at unusual sites like the breast can be difficult, particularly with limited biopsy tissue.
• Immunohistochemistry is valuable, but cytogenetics (fluorescence in-situ hybridization) was crucial for definitive diagnosis in this case.
• Clinicians should consider rare tumors when morphological and immunohistochemical findings are conflicting or inconclusive, underscoring the role of advanced diagnostics.