Histopathological features of the recurrent tumor. A: Multinodular growth pattern without encapsulationis shown. (20x, Hematoxilin-Eosin staining) B: The tumor was composed of solid proliferating uniform short spindle or ovoid cells with vesicular nuclei, and a small amount of cytoplasm (100x, Hematoxilin-Eosin staining). C: The tumors cells were separated by alcian blue positive mucoid material in small areas. (200x, Alcian blue staining).