A 35-year-old Japanese man who had experienced hoarseness for 10 years presented with a vocal cord lesion. A gross examination revealed a left vocal cord polyp occupying two-thirds of the vocal space. The endoscopically resected lesion contained scattered atypical fibroblastic, stellate, or ganglion-like cells with mucoid stroma. Vacuolated cells were also seen. Lymphoplasmacytic infiltrate was largely undetectable. A vocal cord polyp was first suspected, but well-differentiated liposarcoma and inflammatory myofibroblastic tumor (IMT) were included in the differential diagnoses. The tumor cells were positive for anaplastic lymphoma kinase (ALK), calponin, and vimentin, and negative for other smooth muscle markers by immunohistochemistry. Structures resembling myofibroblasts were not observed by electron microscopy, which confirmed abundant rough endoplasmic reticulum in the tumor cells and accumulated lipid droplets in some tumor cells. ALK gene rearrangement was detected by fluorescence in situ hybridization, and TIMP3-ALK fusion was confirmed by 5' rapid amplification of cDNA ends. We diagnosed the lesion as an IMT, and an ALK-rearranged stellate cell tumor may be postulated. This is the first report of a fusion partner gene of ALK in a case of laryngeal IMT.

Department of Anatomic Pathology Pathological Sciences Graduate School of Medical Sciences Kyushu University Fukuoka Japan

Department of Diagnostic Pathology Japanese Red Cross Kochi Hospital Kochi Japan

Department of Otorhinolaryngology Japanese Red Cross Kochi Hospital Kochi Japan

Department of Pathology Charles University Medical Faculty and Charles University Hospital Plzen Pilsen Czech Republic

Department of Pathology Kochi Medical School Kochi University Kochi Japan

Division of Pathology Cancer Institute Japanese Foundation for Cancer Research Tokyo Japan

Equipment of Support Planning Office Kochi University Kochi Japan

Pathology Project for Molecular Targets Cancer Institute Japanese Foundation for Cancer Research Tokyo Japan

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TIMP3::ALK fusions characterize a distinctive myxoid fibroblastic tumor of the vocal cords: a report of 7 cases