Spectrum of precursor and invasive neoplastic lesions in type 1 congenital pulmonary airway malformation: case report and review of the literature

larger than the positive control (108 bp) which represented a SS with a previously characterized usual type of SYT–SSX1 transcript (Figure 1). The presence of the chimaeric product was confirmed by real-time RT-PCR and the reactions were negative for SYT–SSX2 and SYT–SSX4. Finally, the novel fusion was confirmed by DNA sequencing (Figure 2A). The sequence generated was aligned with the previously reported SYT–SSX1, SYT–SSX2 and SYT–SSX4 transcripts using ClustalW software (http://www.ebi.ac.uk/clustalw) and was found to represent a novel fusion between SYT and SSX1. The novel transcript contains most of the upstream 5¢-exon of the SSX1 gene which is not present in the usual SYT–SSX1 fusion (Figure 2B). The usual SYT–SSX fusion transcripts fail to be detected in a small percentage of cases diagnosed as SS in virtually every reported series. Such neoplasms may represent tumours which have a similar morphology to SS, such as a malignant peripheral nerve sheath tumour. Alternatively, these cases may represent tumours with rare variants of the SYT–SSX fusion which have not been detected. Therefore, the documentation of all rare variants is important so that detection strategies can be delineated. Finally, the advent of clinical trials involving targeted drug treatment against tumour-specific genetic events makes the molecular classification of tumours more important than ever before.