Epithelioid Fibrous Histiocytoma With Bulbous Subcutaneous Extension and SQSTM1 :: ALK Fusion

IntroductionEpithelioid fibrous histiocytoma (EFH) is a histopathologically distinct benign cutaneous neoplasm characterized by ALK rearrangement resulting in aberrant anaplastic lymphoma kinase (ALK) expression detectable by immunohistochemistry [1,2].Classically, EFH is composed of epithelioid cells arranged as a dome-shaped nodule in the superficial dermis with an epidermal collarette.Large case series have characterized a fairly narrow spectrum of histopathologic features with nearly all cases confined to the dermis [2-5].Recently in this journal, Dileep et al. reported three cases of EFH with deep dermal and subcutaneous extension [6].Herein, we report an epithelioid fibrous histiocytoma with deep subcutaneous extension and diagnosis further supported by detection of a SQSTM1::ALK fusion by next generation sequencing studies.