Cutaneous soft tissue tumors in the 5th edition of the World Health Organization classification of skin tumors: key updates and new entities

The 5th edition of the World Health Organization (WHO) classification of skin tumors introduces a dedicated chapter on cutaneous soft tissue tumors, providing a comprehensive, standardized reference with updated diagnostic criteria that directly inform routine dermatopathology practice and molecular diagnostics. This edition incorporates several key changes, including newly recognized entities such as EWSR1::SMAD3-rearranged fibroblastic tumor, neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasm, superficial CD34-positive fibroblastic tumor, and CRTC1::TRIM11 cutaneous tumor. Diagnostic terminology has also been refined; for example, the term 'atypical intradermal smooth muscle neoplasm' replaces 'cutaneous leiomyosarcoma' for lesions confined to the dermis, whereas the designation leiomyosarcoma is reserved for tumors with overt subcutaneous infiltration. In addition, epithelioid fibrous histiocytoma has been reassigned to the family of tumors of uncertain differentiation. This review summarizes the key updates and newly recognized entities in the chapter on cutaneous soft tissue tumors in the 5th edition of the WHO classification of skin tumors, emphasizing their clinicopathological and molecular implications.