PMC8717007_01
Histomorphological aspects of thyroid SFT. A: Hypocellular and hypercellular areas (HE, x100); B: Abundant collagen deposits (HE, x200); C: Staghorn blood vessels (HE, x100); D: Entrapment of thyroid follicles (HE, x40).
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Microscopic examination identified a mesenchymal spindle cell proliferation with fascicular and storiform growth pattern with alternation of hypocellular and hypercellular areas (Figure 1A). In hypocellular areas, abundant collagen deposits (Figure 1B) and prominent staghorn blood vessels were identified (Figure 1C). At the margins of the tumor, focal entrapment of thyroid follicles was present (Figure 1D).
Immunohistochemical profile of thyroid SFT. Strong and diffuse positivity of tumor cells for: A. CD34 (IHC, anti-CD34 antibody, x40); B. BCL-2 (IHC, anti-BCL-2 antibody, x200); C. CD99 (IHC, anti-CD99 antibody, x40); D. vimentin (IHC, anti-vimentin antibody, x40).
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BCL-2 (Figure 2B), CD99 (Figure 2C) and vimentin positive (Figure 2D) and negative for TTF-1 (Figure 3A), S100 (Figure 3B), CD68, NSE, desmin (Figure 3C) and SMA (Figure 3D) with a Ki-67 proliferation index <1%. Based on morphological and immunohistochemical features, the final diagnosis was primary solitary fibrous tumor of thyroid gland.
Immunohistochemical profile of thyroid SFT. Total negativity for: A. TTF-1 in tumor cells, with positivity in thyroid follicular cells (IHC, anti-TTF-1 antibody, x40); B. S100 protein with aberrant cytoplasm positivity (IHC, anti-S100 antibody, x200); C. desmin (IHC, anti-desmin antibody, x40); D. SMA in tumor cells, with positivity in smooth muscle layer of blood vessels (IHC, anti-SMA antibody, x100).
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BCL-2 (Figure 2B), CD99 (Figure 2C) and vimentin positive (Figure 2D) and negative for TTF-1 (Figure 3A), S100 (Figure 3B), CD68, NSE, desmin (Figure 3C) and SMA (Figure 3D) with a Ki-67 proliferation index <1%. Based on morphological and immunohistochemical features, the final diagnosis was primary solitary fibrous tumor of thyroid gland.