Tumors of the Soft Tissue: Using Molecular Tools to Aid in the Diagnosis of Soft Tissue Tumors and the Management of the Sarcoma Patient

Abstract

Soft tissue tumors are rare. Soft tissue tumors in the skin are even rarer, and use of molecular testing for soft tissue tumors in the skin is rarer still. With that said, molecular diagnostics has a small but definite (and growing) role in the diagnosis and management of the sarcoma patient. Over the past several decades, the uncovering of soft tissue tumor-specific molecular events, including chromosomal translocations with fusion genes and proto-oncogene amplifications, has advanced the understanding of the biology of these enigmatic tumors, and in some cases, have aided in their re-classification. These same events have led to the development of tumor-specific molecular assays. When used appropriately, as an adjunct to conventional diagnostic methods, the molecular assay can be the dermatopathologist’s most powerful tool for achieving diagnostic accuracy in select settings. As in other disciplines, the discovery of oncogenic drivers, such as fusion genes and proto-oncogene mutations, should lead to prognostic and theranostic applications. Few of these currently exist for soft tissue tumors, but the list is growing, and soon this class of tumors will join others, embarking toward the world of personalized medicine. This chapter covers select soft tissue tumors with characteristic molecular events, with an emphasis on diagnostic applications. Tumors that are more commonly encountered in the skin are highlighted, but it should be noted that virtually any soft tissue malignancy can expand into the skin or metastasize to the skin. Other molecular applications for soft tissue tumors, and specifics on methods and testing strategies, including practical points, are also discussed.