The molecular biology of soft tissue sarcomas

Sarcomas: genetics, signalling, and cellular origins. Part 1: The fellowship of TET

Sarcomas comprise some of the most aggressive solid tumours that, for the most part, respond poorly to chemo- and radiation therapy and are associated with a sombre prognosis when surgical removal cannot be performed or is incomplete. Partly because of their lower frequency, sarcomas have not been studied as intensively as carcinomas and haematopoietic malignancies, and the molecular mechanisms that underlie their pathogenesis are only beginning to be understood. Even more enigmatic is the identity of the primary cells from which these tumours originate. Over the past 25 years, however, several non-random chromosomal translocations have been found to be associated with defined sarcomas. Each of these translocations generates a fusion gene believed to be directly related to the pathogenesis of the sarcoma in which it is expressed. The corresponding fusion proteins provide a unique tool not only to study the process of sarcoma development, but also to identify cells that are permissive for their putative oncogenic properties. This is the first of two reviews that cover the mechanisms whereby specific fusion/mutant gene products participate in sarcoma development and the cellular context that may provide the necessary permissiveness for their expression and oncogenicity. Part 1 of the review focuses on sarcomas that express fusion genes containing TET gene family products, including EWSR1, TLS/FUS, and TAFII68. Part 2 (J Pathol 2007; DOI: 10.1002/path.2008) summarizes our current understanding of the genetic and cellular origins of sarcomas expressing fusion genes exclusive of TET family members; it also covers soft tissue malignancies harbouring specific mutations in RTK-encoding genes, the prototype of which are gastrointestinal stromal tumours (GIST).

Pathological Society of Great Britain and Ireland, 176th meeting. London, United Kingdom, 7-9 January 1998. Abstracts

The identification of specific chromosome translocations in various sarcomas and the elucidation of their molecular consequences has raised the possibility of detecting their presence for diagnostic and prognostic purposes in a manner analogous to the haematological malignancies. However, it is important to correlate particular translocations, and also other genetic aberrations, with current histological diagnoses and the behaviour of tumours, in order to assess the potential benefits, if any, of identifying rearrangements. Recent developments which enable specific translocations to be identified in archival material are likely to play an increasing role in the assessment and, eventually, the management of patients with sarcomas.

Advances in the understanding of the molecular pathology of connective tissue neoplasms

Although primary malignant neoplasms of the connective tissues are uncommon, they have been subjected to intense study by modern molecular and other analytical techniques. Aberrations of genes and their products are providing insight into aetiopathogenesis and indicating improved methods of histopathological diagnosis and patient management.

Diagnosis of Ewing's sarcoma and related tumours by detection of chromosome 22q12 translocations using fluorescence in situ hybridization on tumour touch imprints

It is increasingly recognized that the identification of t(11;22)(q24;q12) is a useful aid in the accurate diagnosis of Ewing's sarcoma and related tumours. However, cytogenetic studies have a low success rate and adequate tumour is not always available. This study describes the use of fluorescence in situ hybridization (FISH) to detect translocations at 22q12, the site of the EWS gene involved in t(11;22)(q24;q12), on tumour touch imprints made from true cut core-needle biopsy and frozen tumour. Of the seven tumours analysed, five diagnosed as Ewing's sarcoma or primitive neuroectodermal tumour demonstrated chromosome translocation at 22q12. This is a rapid and reliable method to detect a diagnostically relevant chromosome translocation using minimal amounts of fresh or frozen tumour.