Comparison of β-Catenin and LEF1 Immunohistochemical Stains in Desmoid-type Fibromatosis and its Selected Mimickers, With Unexpected Finding of LEF1 Positivity in Scars.

β-catenin immunohistochemical stain can be useful in the diagnosis of many tumors including desmoid-type fibromatosis (DTF). Lymphoid enhancer-factor 1 (LEF1), a recently emerged marker, is part of the Wnt pathway with β-catenin but has not been studied in DTF. We performed LEF1 and β-catenin immunohistochemistry in DTF (n=26), superficial fibromatosis (n=19), sclerosing mesenteritis (n=12), gastrointestinal stromal tumor (n=17), and cutaneous scar (n=14) using tissue microarray and whole sections. The staining intensity was scored as strong (visible at ×2 objective, value of 3), moderate (visible at ×4, value of 2), weak (visible at ×10, value of 1), and negative (not visible at ×10, value of 0). The percentage of positive nuclei was recorded in 10% increment. Histologic scores were generated by multiplying numerical value of intensity and percentage of positive nuclei. A score of at least 10 was defined as positive. Eighteen of the 25 DTF were positive for LEF1 while 12 of 25 were positive for β-catenin (1 excluded due to loss of tissue). Gastrointestinal stromal tumor cases were negative for both markers. All superficial fibromatoses were negative except 2 cases with weak positivity for LEF1 but not β-catenin. Only 2 case of sclerosing mesenteritis were weakly positive for LEF1 but negative for β-catenin. Ten of 14 scars were positive for LEF1 but only 1 of them was weakly positive for β-catenin. In conclusion, this study demonstrated that LEF1 may be a useful marker in the differential diagnosis of DTF in certain contexts. However, caution should be exercised since LEF1 positivity can also be seen in scars.