Low-grade myofibroblastic sarcoma of the tongue with difficulty of diagnosis: A case report and review of the literature

We describe a case of low-grade myofibroblastic sarcoma (LGMS) on the dorsum of the tongue. A 41-year-old Japanese man noticed that a mass on the dorsal surface of the tongue had been present for 8 months. Computed tomography showed a homogeneously enhancing mass measuring 16 × 14 mm in the midline of the tongue. Magnetic resonance imaging showed a homogeneously enhancing mass with an almost clear margin on post-contrast T1-weighted imaging. The lesion was homogeneous with high signal intensity on T2-weighted imaging. The patient underwent excisional biopsy. Histologically, the tumor had an indistinct margin and was composed of spindle-shaped cells arranged in cellular fascicles. The cell nuclei showed signs of mild atypia. Positive staining for desmin and less strong staining for α-smooth muscle actin revealed that the tumor cells were myofibroblasts or smooth muscle cells. The tumor cells were negative for h-caldesmon. The MIB-1 labeling index of the tumor was 4.9 %. Thus, based on the histopathological, immunohistochemical and imaging findings, the tumor was finally diagnosed as LGMS. We reviewed the literature on the immunohistochemistry of LGMS. We suggest that immunohistochemistry is helpful in the differential diagnosis of LGMS.