Histologic features, growth patterns and classification of atypical thymomas

Area of Science:

• Pathology
• Oncology
• Histology

Background:

• Atypical thymomas are rare primary thymic epithelial neoplasms.
• They show conserved organotypical features but possess atypical cytological characteristics.
• The full spectrum of their histologic features and growth patterns is not well-documented.

Purpose of the Study:

• To review the diverse morphologic appearances of atypical thymomas.
• To emphasize the wide spectrum of histologic features displayed by these neoplasms.
• To discuss current nomenclature and diagnostic approaches.

Main Methods:

• Review of literature on atypical thymomas.
• Analysis of histologic features and growth patterns.
• Discussion of differential diagnoses and biologic behavior.

Main Results:

• Atypical thymomas present with epithelioid/squamoid and spindle cell subtypes.
• Histologic features can mimic thymic carcinomas or metastatic disease, particularly squamous cell carcinoma.
• These subtypes can occur alone, in combination, or with conventional thymoma types.

Conclusions:

• Atypical thymomas have an intermediate biologic behavior between conventional thymoma and thymic carcinoma.
• These tumors exhibit aggressive behavior with increased metastasis risk.
• Correct and timely diagnosis is of utmost importance for patient management.