Fig. 3.

Histological findings

(A–C) H&E stain (A, 40 ×; B, 100 ×; C, 400 ×) showed tumor cells presenting a diffuse growth pattern with abundant slit-shaped vessels in the central area. Ten high power fields (400 ×) revealed mitosis 5 or less (white arrow).

(D) Silver staining (100 ×) revealed linear structures indicating collagen fibers.

(E–H) Immunohistochemistry examination of vimentin (E, 100 ×), STAT6 (F, 100 ×), and CD34 (G, 100 ×) was positive. Ki-67 staining (H, 100 ×) showed a proliferative index of 15%. No other immunostainings were positive.