OBJECTIVETo study clinical and histopathological features, and diagnosis of mediastinal tumours of haematopoietic and lymphoid tissues (MTHL).

METHODSForty cases of MTHL were analyzed for clinicopathology by microscopy and immunohistochemical staining and in situ hybridization, according to the updated 2008 WHO classification of tumours of haematopoietic and lymphoid tissues.

RESULTSIn 40 cases of MTHL, there were 20 males and 20 females. The ratio of male/female was 1:1. The mean age was 31.8 years and median age was 29 years (range, 12 - 70 years).Superior vena cava syndrome was observed in 28 cases. The specimens of 4 cases were obtained by lumpectomy, whereas 36 cases by biopsy (25 cases by thoracoscopy, 1 by core needle aspiration). Twenty cases lay in anterior mediastinum, and 2 in posterior, 1 in superior, 8 in anterior and superior, 2 in posterior and superior, 2 in anterior and middle, 1 in middle and anterior mediastinum.Frozen section were performed in 28 cases, and 17 cases were diagnosed as tumours of haematopoietic and lymphoid tissues (consistency ratio was 60.7%). Twelve cases were classical Hodgkin lymphomas (cHL) (8 were nodular sclerosis subtype, and 3 were mixed cellarity, 1 was lymphocyte-rich subtype), and 10 were primary mediastinal (thymic) large B cell lymphoma (PMBCL), 10 were precursor lymphocyte neoplasm [8 were T lymphoblastic leukemia/lymphomas (T-LBL), 2 were B-LBL], 1 was MALT lymphoma, 1 was composite lymphoma (PMBCL and cHL), 2 were myeloid sarcomas, 4 were gray zone lymphomas (GZL) (3 had morphology reminiscent of cHL, and 1 of DLBCL, all cases were positive for CD20, PAX5, CD30 and CD15).EBER were detected in 11 cases by in situ hybridization, 2 of which were positive (18.2%), and the 2 positive cases were cHL.

CONCLUSIONSMTHLs occur predominantly in adolescents and young adults, mainly present as superior vena cava syndrome and anterior mediasinal masses. cHL, PMBCL, T-LBL were the most common MTHLs.GZLs mainly occur in young adults, those whose morphology reminiscent of cHL, immunohistochemistry reminiscent of PMBCL, and vice versa. Thoracoscopy, frozen section and a suitable panel of antibodies were practical approaches to MTHL.