Epithelioid Fibrous Histiocytoma with CARS-ALK Fusion: First Case Report

Epithelioid fibrous histiocytoma (EFH) is a type of uncommon skin tumor mostly harboring Anaplastic Lymphoma Kinase (ALK) gene rearrangement, with different fusion partners reported. Whether this tumor is a separate entity or has a relationship with conventional fibrous histiocytomas is still a matter of debate. Benign course is the rule after complete surgical excision. A rare subtype of EFH with fusiform cells has been described, with specific fusion partners. Inflammatory myofibroblastic tumor (IMT) is a type of soft tissue tumor rarer than EFH, and it can display distant metastases. Some cases of primary cutaneous IMT included two with Cysteinyl-tRNA Synthetase 1 (CARS)-ALK rearrangement. IMT can have the same fusion partners as EFH, such as DCTN1, TMP3 or EML4 genes. We report the case of a 42-year-old woman presenting EFH with fusiform morphology harboring CARS-ALK fusion and discuss similarities and differences with IMT.