Benign solitary fibrous pleural tumour. Evidence of primitive features and complex genomic imbalances, including loss of 20q

Aims: Cytogenetic data on solitary fibrous tumours (SFT) are very limited. We studied a benign pleural SFT for its ultrastructural and immunohistochemical details, and made cytogenetic analyses for comparison with other genetic and ultrastructural studies of SFT. Results: Immunohistochemistry showed strong positivities for CD34 and vimentin, but no reactions with anti-cytokeratins and epithelial membrane antigens. Electron microscopy revealed primitive desmosomes in our SFT. The results thus evinced fibroblast-like cells with intermediate epithelial-mesenchymal character. Comparative genomic hybridization of the tumour revealed losses of 1p33→pter, 17pter-q21, entire copies of chromosomes 19 and 22, and gains of 1p21-p22, 2q23-q32.3, 3p12-q13.2, 4p14-q28, 6p12-q21, 9p21→pter and 13q21-q31. Furthermore, there was loss of 20q, as was previously reported elsewhere in a case of benign and a case of malignant SFT. Conclusions: The results furnish further evidence of the involvement of -20q in SFT. In addition, they show that SFT may have complex genomic imbalances and primitive features, despite having a benign appearance.