Cutaneous Myeloid Sarcoma Mimicking Blastic Plasmacytoid Dendritic Cell Neoplasm as the Initial Manifestation of Acute Myeloid Leukemia

Myeloid sarcoma is a rare extramedullary proliferation of immature myeloid cells that may precede or accompany acute myeloid leukemia (AML) [Citation1]. Cutaneous involvement is uncommon and frequently misdiagnosed because of morphologic and immunophenotypic overlap with other hematologic malignancies [Citation1]. We report a diagnostically challenging case of a 59-year-old woman who developed rapidly progressive, multifocal fungating cutaneous tumors that evolved over approximately three months. Initial biopsies demonstrated features concerning for both myeloid sarcoma and blastic plasmacytoid dendritic cell neoplasm (BPDCN). Focused immunohistochemical evaluation revealed strong lysozyme expression with absence of CD123 and TCL1A, supporting a diagnosis of AML-associated myeloid sarcoma [Citation2]. Subsequent bone marrow evaluation confirmed AML. This case highlights the importance of considering myeloid sarcoma in rapidly enlarging cutaneous tumors and underscores the critical role of targeted immunophenotyping, recognizing that no single marker or panel has absolute sensitivity or specificity, in avoiding diagnostic delay and enabling timely initiation of appropriate systemic therapy.