Actual Information for Pathologists making Diagnoses of Thymomas updated:2009.10.12

START here thymoma.de

this is a backup of the Stanford website http://surgpathcriteria.stanford.edu/thymus/thymoma/index.html please check there first, come back if the site has gone.

Thymoma

Definition

• Thymic epithelial cell neoplasm lacking overtly malignant cytologic features

Diagnostic Criteria

• The currently most widely used classification is that of the WHO 2004
  • A number of other classifications have been used or proposed
• See individual entries for each type by clicking on the links below
• Type A
  • Thymoma composed of bland spindle to oval cells with few to no lymphocytes
• Type AB
  • Thymoma with a mixture of lymphocyte-poor and lymphocyte rich areas
• Type B1
  • Thymoma exhibiting areas reminiscent of both normal thymic cortex and medulla
• Type B2
  • Thymoma with prominent large epithelial cells with an admixture of numerous lymphocytes
• Type B3
  • Thymoma composed of sheets of epithelial cells with mild to moderat atypia and scant lymphocytes
• Micronodular Thymoma with Lymphoid Stroma
  • Thymoma composed of multiple epithelial nodules surrounded by prominent lymphoid stroma containing mature B and T cells and devoid of epithelial cells
• Metaplastic Thymoma
  • Thymoma composed of alternating areas of epithelial cells and bland slender spindle cells
• Combined Thymoma
  • A thymoma exhibiting more than one thymoma type pattern, or
  • A combination of thymoma and thymic carcinoma
• Malignant Thymoma
  • Generally used to refer to any of the above thymoma types that is behaving aggressively
  • Thymic carcinoma is the preferred term for a cytologically malignant epithelial thymic neoplasm

Staging

• (Modified Masaoka - there is no official AJCC TNM staging for thymoma)

• Lymphatic metastases are rare
• Hematogenous metastases are exceedingly rare
• There is no significant difference in disease free or overall survivall between Stage I and II (Gupta et al.. Arch Pathol Lab Med. 2008 Jun;132(6):926-30.)

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342