Overview of Malignant Thymic Neoplasms
 WHO type A thymoma (spindle cell thymoma) shows characteristic cytomorphology of the tumor cells with elongated spindle cells displaying nuclei that contain dispersed chromatin and absence of nucleoli. |
 WHO type B thymoma (lymphocyte rich) shows large epithelioid cells  with vesicular nuclei and indistinct rim of amphophilic cytoplasm surrounded by dense population of small lymphocytes. |
TERMINOLOGY
Definitions
Primary malignant thymic neoplasms are derived from thymic epithelium, stroma, germ cells, or lymphoid component and include
Primary thymic epithelial neoplasms
Well-differentiated primary thymic epithelial neoplasms (thymoma)
Moderately differentiated primary thymic epithelial neoplasms (atypical thymoma)
Poorly differentiated primary thymic epithelial neoplasms (thymic carcinoma)
Thymic lymphoproliferative disorders
Hodgkin disease
Lymphoblastic lymphoma
Mediastinal diffuse large B-cell lymphoma
Other types of mediastinal lymphomas
Germ cell tumors arising in the mediastinum
Teratomatous lesions
Seminoma
Yolk sac tumor
Choriocarcinoma
Embryonal carcinoma
Neuroendocrine carcinomas of the thymus
Well-differentiated neuroendocrine carcinoma (thymic “carcinoid”)
Moderately differentiated neuroendocrine carcinoma (“atypical carcinoid” of thymus)
Poorly differentiated neuroendocrine carcinoma (small cell and large cell neuroendocrine carcinomas)
Sarcomas
Liposarcoma
Leiomyosarcoma
Epithelioid hemangioendothelioma
Chondrosarcoma
Osteosarcoma
Chordoma
Fibrosarcoma and malignant fibrous histiocytoma
Synovial sarcoma
Malignant peripheral nerve sheath tumors
Rhabdomyosarcoma
Alveolar soft parts sarcoma
Mesenchymal chondrosarcoma
EPIDEMIOLOGY
