Update on Cutaneous Soft Tissue Tumors

The classification of cutaneous soft tissue tumors is undergoing rapid evolution, driven by advances in molecular pathology and the identification of novel gene fusions. This presentation reviews recent developments that are reshaping the diagnostic approach to these neoplasms and influencing the upcoming WHO Classification.

Topics include the recognition of superficial neurocristic FET::ETS fusion tumors as a distinct entity separate from conventional Ewing sarcoma, the expanding spectrum of ALK-rearranged mesenchymal and vascular neoplasms, and the evolving relationship between epithelioid fibrous histiocytoma and superficial ALK-rearranged myxoid spindle cell tumors. Additional developments include new insights into superficial CD34-positive pleomorphic fibroblastic tumor, GLI1-altered mesenchymal neoplasms, PRRX1-rearranged fibroblastic tumors, OGT-rearranged mesenchymal neoplasms, and acral fibrochondromyxoid tumor.

The lecture will emphasize practical histopathologic features, immunophenotypic patterns, and the growing role of next-generation sequencing and methylation profiling in routine diagnosis. Particular attention will be given to diagnostic pitfalls and the clinical significance of distinguishing these newly recognized entities from their more aggressive histologic mimics.

Together, these discoveries illustrate the transition from morphology-based classification toward an integrated morphologic and molecular framework, with important implications for patient management and future tumor classification systems.