Abstract
Gene rearrangements involving the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase gene have been identified in various neoplasms, including inflammatory myofibroblastic tumor and epithelioid fibrous histiocytoma. We present an ALK-rearranged cutaneous soft tissue tumor with unique morphologic and immunophenotypic features that are not shared by other entities with ALK rearrangements. The six cases involved two females and four males, aged 18-84 (mean 51) years old. Three tumors were on the back and three on the lower extremities (thigh, knee, shin); ranging from 0.5 to 5.6 (mean 2.1) cm. Four were confined to the dermis; two involved the subcutis. All six cases were characterized by the presence of spindled to ovoid cells arranged in concentric whorls and cords against a myxoid to myxohyaline stroma and relatively cellular aggregates of plump ovoid to epithelioid cells. Four cases showed distinct hyalinized blood vessels. Both cases that involved the subcutis showed peripheral lipofibromatosis-like areas. Tumor-infiltrating lymphocytes were absent to moderate. Severe cytologic atypia or conspicuous mitotic activity was not identified. Immunohistochemically, all tumors diffusely expressed ALK (D5F3) and CD34. All but one tumor was diffusely positive for S100 protein. All tumors were negative for EMA, AE1/AE3, SMA, and SOX10. Next-generation sequencing revealed ALK fusions with FLNA (3 cases), MYH10 (2 cases), and HMBOX1 (1 case) as the partner genes. In all six cases, the breakpoints involved exon 20 of ALK, which preserves the receptor tyrosine kinase domains of ALK in the fusion product. Of the four cases with limited follow-up information (2-18 months), none recurred. In conclusion, we report an ALK-rearranged cutaneous soft tissue tumor characterized by the presence of myxoid spindle cell whorls and cords, and co-expression of ALK, CD34, and frequently S100 protein, we term "superficial ALK-rearranged myxoid spindle cell neoplasm".
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
