This issue of Pathology Case Reviews provides an update on recent advances in the diagnosis of selected bone and soft tissue tumors. As in previous issues of the journal, the articles aim to provide practical, up-to-date information regarding the clinical, radiographic, and histologic features of each tumor, including a historical perspective. Our increased understanding of the molecular pathogenesis of mesenchymal tumors has made the present a very exciting time in bone and soft tissue pathology, with improved diagnostic accuracy, targeted therapies, and a reevaluation of tumors long believed to be reactive, as opposed to neoplastic. Therefore, each case discussion emphasizes the impact of these advances on diagnosis, classification, and/or therapy. Fibrous dysplasia represents the prototypical “fibro-osseous” lesion of bone and has an important developmental component in some patients: the McCune-Albright syndrome. Diagnostically, fibrous dysplasia can present a challenge because of the variety of neoplastic and reactive fibro-osseous proliferations in bone, including some low-grade malignancies. Dr Fritchie illustrates an example of a classic case and reviews its diagnostic features, differential diagnosis, and those recent developments in our understanding of the G protein signaling pathway that have allowed us to better understand both syndromic and isolated tumors. “Small round blue cell” tumors are among the most diagnostically challenging malignancies for bone and soft tissue pathologists. Immunohistochemistry, while still useful for the diagnosis of many of the entities in this differential diagnosis, has gradually been supplanted by molecular techniques, owing to the presence of specific, reproducible, chromosomal translocations in many of these tumors. Mesenchymal chondrosarcoma, discussed by Drs Borys and Canter, has until recently remained an exception to this rule, although even here specific genetic events may recently have been identified. The unique clinicopathologic features of mesenchymal chondrosarcoma are discussed in the article, as well as the utility and limitations of immunohistochemistry and molecular techniques in this setting. Dr Dry provides an extensive review on our current understanding of the well-differentiated and dedifferentiated family of liposarcomas. The classification of well-differentiated lipomatous tumors into benign and malignant categories has historically been challenging but can be now made with confidence owing to the discovery of reproducible, specific, chromosomal changes in this family of tumors. Liposarcomas also serve as a paradigm for ways in which new immunohistochemical tests can be derived from an improved understanding of the molecular changes in a given tumor. Drs Torres-Mora and Oliveira present a case of aneurysmal bone cyst, an uncommon bone tumor that can present diagnostic difficulties for a variety of reasons, including its morphological overlap with a variety of other neoplastic and nonneoplastic bone lesions and its occurrence both in primary and in secondary forms. The discussion aims to provide insights into the genetic events that characterize aneurysmal bone cyst and shows how these discoveries have opened a new window into better understanding the biology of those mesenchymal lesions that straddle the line between reactive and neoplastic proliferations.Finally, Dr Vogel describes an example of a poorly differentiated chordoma. Although the clinicopathologic features of conventional chordomas have been well characterized over the years, their molecular pathogenesis has remained elusive. Improved understanding of notochordal development, including the critical role of brachyury, has allowed for improved diagnosis of all chordomas, including rare poorly differentiated variants. The importance of the SMARCB1/INI1 gene in these tumors is also discussed, including those ways in which better understanding of the role of this tumor suppressor may ultimately allow for targeted therapy. We want to thank all the contributors for their tremendous efforts and for sharing their expertise and knowledge. The applications of our improved understanding of the molecular pathogenesis of soft tissue and bone tumors continue to evolve, and we hope that the current issue provides a useful update as to their impact on routine pathology practice.
Read full abstract
Jul 11, 2024
Mónica Alexandra Acosta Vargas Mónica Alexandra Acosta Vargas + 3
Open Access