The t(12;15)(p13;q25) translocation, a recurrent
chromosomal abnormality of congenital
fibrosarcoma, leads to the expression of a Tel-TrkC fusion transcript. To determine whether detection of the chimeric
protein may be helpful for the diagnosis of congenital
fibrosarcoma, immunohistochemistry was performed with an anti-TrkC antibody on 26 spindle cell tumours of newborn or young children (n=19) or adults (n=7). Four out of five congenital
fibrosarcomas showed TrkC immunoreactivity with cytoplasmic paranuclear staining. However, TrkC immunoreactivity was not restricted to congenital
fibrosarcoma and was observed in infantile
myofibromatosis, congenital haemangiopericytoma,
desmoid tumour, nodular
fasciitis, fibrous
hamartoma, inflammatory myofibroblastic tumour, and adult
fibrosarcoma. RT-PCR analysis was performed on nine cases, including four congenital
fibrosarcomas, for which frozen material was available. Tel-TrkC transcripts were detected by RT-PCR in the four congenital
fibrosarcomas analysed, but not in the five other spindle cell tumours. Furthermore, several Tel-TrkC transcripts encoding for
kinase isoforms of the Tel-
TrkC protein were detected in congenital
fibrosarcoma and may be involved in
oncogenesis. The reciprocal TrkC-Tel transcript was detected in only one congenital
fibrosarcoma. While the detection of a Tel-TrkC fusion transcript is a recurrent feature of congenital
fibrosarcoma, TrkC immunoreactivity does not appear specific for the diagnosis of fibromatous paediatric tumours.