Alice Benedetti

bcl-2 EXPRESSION IN PLEURAL AND EXTRAPLEURAL SOLITARY FIBROUS TUMOURS

This study evaluated the immunoreactivity for bcl‐2, a molecule involved in the control of programmed cell death, in cases of pleural (14) and extrapleural (2) solitary fibrous tumour (SFT), malignant mesotheliomas of different histological types, and a variety of extrapleural CD34‐positive and CD34‐negative spindle‐cell tumours. In all SFTs, strong and diffuse immunostaining was demonstrated with anti‐bcl‐2 antibody, sharply contrasting with the complete lack of staining observed in all mesotheliomas. The specificity of immunodetection of bcl‐2 in SFT was confirmed by immunoblot analysis, showing a band consistent with the bcl‐2 protein. At extrapleural locations, strong bcl‐2 immunoreactivity was observed in Schwannoma (2/3 cases), synovial sarcoma (4/4 cases), and all cases of CD34‐positive gastrointestinal stromal tumour (GIST; 10/10 cases). Most sarcomas were bcl‐2‐negative. Lack of bcl‐2 expression was demonstrated in tumours which can pose problems in the differential diagnosis of SFT and can exhibit haemangiopericytoma‐like features, including haemangiopericytoma (3 cases), dermatofibrosarcoma protuberans (16 cases), and deep‐seated fibrous histiocytoma (3 cases). The constitutive expression of bcl‐2 in SFT widens the spectrum of available markers for these tumours, providing a useful adjunct to their differential diagnosis in difficult cases at pleural and extrapleural sites, and contributing to the understanding of their histogenesis and molecular pathogenesis.

Cyclin-Dependent Kinase 6 (PLSTIRE) Expression in Normal Thymus, Thymomas, and T-Cell Lymphoblastic Lymphoma

Different benign and malignant processes should be included in the differential diagnosis of a patient presenting with a mediastinal mass, depending on the age and clinical features. These include thymoma, T-cell lymphoblastic lymphoma/leukemia, thymic follicular hyperplasia, true thymic hyperplasia, and others. Thymomas are mediastinal neoplasms arising from thymic epithelial cells that exhibit heterogeneous morphology and, in most cases, are admixed with various proportions of non-neoplastic cortical thymocytes1–5. The histological diagnosis of thymoma is usually based on the recognition of neoplastic epithelial cells, but some diagnostic problem can be encountered in cases with abundant lymphoid component, especially when only small tissue fragments (e.g. by mediastinoscopy) or cytological material are available. Immunohistochemistry can provide some help in difficult cases by demonstrating more precisely the presence of epithelial cells using cytokeratin-specific antibodies6. An extremely precise characterization of cortical thymocytes can be obtained by immunophenotypic demonstration of several membrane, cytoplasmic or nuclear antigens such as CD1, coexpressed CD4 and CD8 antigens, cytoplasmic CD3 and nuclear Terminal deoxynucleotydil transferase (TdT)7.