Objective: ALK-related superficial soft tissue tumors represent an emerging category of neoplasms in daily pathology practice. We report the case of a 49-year-old Caucasian woman with an ALK-related neoplasm who presented with a 1,5 cm nodule on her left thigh.

Case Report: The lesion was excised and histopathologically evaluated. Microscopic examination revealed a well-circumscribed nodule composed of epithelioid and oval-to-spindle cells. Although some morphological features were shared with epithelioid fibrous histiocytoma (EFH), there were no epidermal collarettes. In addition, significant storiform architecture and also foamy histocyte groups were detected in the lesions. ALK positivity was observed in both the immunohistochemical and FISH studies. Superficial ALK-rearranged Myxoid Spindle Cell Neoplasms (SAMS) were first considered in the differential diagnosis due to their prominent storiform structures. The lesion shared both EFH and SAMS morphology. Finally, we reported the case as `EFH with SAMS-like features`. The patient showed no evidence of recurrence during a 10-month follow-up.

Conclusion: This case presents the diagnostic challenges in ALK-positive neoplasms. Superficial soft tissue tumors associated with ALK include a heterogeneous group of lesions that may share similar morphological features. We believe that a generic term, ALK-Rearranged Superficial Mesenchymal Neoplasms (ARSMN), may serve as a more inclusive diagnostic label for these entities in routine pathology practice.