TUMORS OF THE MEDIASTINUM
THYMOMA AND THYMIC CARCINOMACARCINOMA
Classification of Thymic Tumors
Historically
The descriptive scheme
The scheme based on topographic and morphofunctional characteristics
Müller-Hermelink scheme comprises the following 5 types
The World Health Organization (WHO) Classification of Tumors of the Thymus and other thoracic tumors
Thymoma and Thymic Carcinoma
General Features
Thymoma
Location of thymoma
Radiographically
Fine-needle aspiration
Pathologic Features of Thymoma
Grossly
“Microthymomas”
Microscopically
By electron microscopy
Immunohistochemistry
Classification of Thymoma and Thymic Carcinoma
The subtypes of thymomas included in the WHO classification
Type A Thymoma (Spindle Cell; Medullary)
Type AB Thymoma (Mixed)
Type B1 Thymoma (Lymphocyte-Rich; Lymphocytic; Predominantly Cortical; Organoid)
Type B2 Thymoma (Cortical)
Type B3 Thymoma (Epithelial; Atypical; Squamoid; Well-Differentiated Thymic Carcinoma)
Rare subtypes of thymoma that do not easily fit into the A-B nomenclature include
Micronodular thymoma
Metaplastic thymoma
Microscopic thymoma (nodular hyperplasia)
Cytology
Limitations of the procedure
Thymic Carcinoma
Thymic tumor
Thymic Carcinoma
Differences from other conventional types of thymoma
Diagnosis
Squamous Cell Carcinoma (SCC)
Basaloid Carcinoma
Differential diagnosis
Mucoepidermoid Carcinoma
Lymphoepithelioma-Like Carcinoma
Clear cell carcinoma
Sarcomatoid Carcinoma (Carcinosarcoma)
“Phenotypic switch”, myoid cells, “triton tumor”, metaplastic thymoma
“orthotopic” counterpart
Adenocarcinomas
NUT (midline) carcinoma
Undifferentiated (Anaplastic) Carcinoma
Rare variants of thymic carcinomas
Cervical Tumors of Thymic or Branchial Pouch Derivation
Ectopic (cervical) thymoma
Ectopic hamartomatous thymoma
Spindle epithelial tumor with thymus-like elements (SETTLE
Microscopically
Differential diagnosis: synovial sarcoma
Carcinoma with thymus-like elements (CASTLE)