Abstract
Anaplastic lymphoma kinase (ALK) rearrangements have emerged as a defining molecular alteration across a wide spectrum of cutaneous mesenchymal and melanocytic neoplasms with diverse clinical, histologic, immunophenotypic, and biologic features. This article describes several distinct ALK-rearranged cutaneous neoplasms: epithelioid fibrous histiocytoma, superficial ALK-rearranged myxoid spindle cell neoplasm, nonneural granular cell tumor, Spitz melanocytic neoplasms, and other emerging entities. ALK overexpression by immunohistochemistry and confirmatory molecular testing, when necessary, plays a critical diagnostic role. The expanding spectrum of ALK-rearranged cutaneous tumors underscores the value of an integrated diagnostic approach to ensure accurate diagnosis and guide clinical management.