PMC7367732_01
Preoperative CT scans showing a large tumor in the nasopharynx. (A) Head CT image showing dense mass of nasopharyngeal soft tissue, protruding into the cavity, with regular shape and uniform density. The left eustachian tube and pharyngeal orifice are not visible, while the right pharyngeal crypt appears shallow. (B) Nasopharyngeal CT scan showing a mass-like shadow on the posterior lateral wall of the left nasopharyngeal roof. The enhanced scan image showing uneven density in the arterial phase (C). Areas with intense dye uptake in the venous phase, and small patchy low-density shadows (D). Postoperative head CT showing that the tumor is completely resected (E).
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The left eustachian tube and pharyngeal orifice had disappeared and the right pharyngeal crypt had become shallow (Figure 1A). To confirm the diagnosis, enhanced CT of the nasopharynx was performed, revealing a mass-like shadow on the posterior lateral wall of the left nasopharyngeal roof (Figure 1B). The enhanced CT image was very uneven in the arterial phase (Figure 1C) but became intense in the venous phase, and small, patchy, low-density shadows were observed (Figure 1D). Postoperative head CT and video laryngoscopy showed that the tumor was completely resected (Figure 1E), and there was no tumor recurrence following a 14-month follow-up after tumor resection.
Microphotographs showing the histopathological features of the tumor. (A) Dense areas with cellular proliferation alternating with hypocellular areas (H&E; x40). (B) Area of the tumor showing disorganized cellular arrangement (H&E; x40). (C) Area with tumor cells arranged in stripes (H&E; x100). (D) Area with tumor cells arranged in storiform pattern (H&E; x100). (E) Multinucleated giant cells deposited in a myxoid stroma (H&E; x100). (F) Multinucleated giant cells deposited in a hyaline stroma (H&E; x200). (G) Interstitial vessels with hyaline degeneration (H&E; x100). (H) Hypercellular areas showing fusiform or oval cells, with no apparent atypia, few cytoplasm, large and deep stained nuclei, and oval nuclei as well as some vacuolated nuclei and some tumor cells with nucleoli. Mitotic figures were 2 per 50 high-power fields (H&E; x400). (I) Multinucleated giant cells varying in size and shape showing nuclei nested in the cytoplasm in a wreath-like and lobulated-shape (H&E; x400).
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Histologically, low-power microscopy revealed that the tumor comprised areas of moderately proliferating bland spindle- or stellate-shaped cells alternating with hypocellular areas (Figure 2A). While some areas were composed of compactly proliferating spindle-shaped cells arranged in a storiform or fascicular growth pattern, there were other areas where tumor cells were randomly distributed (Figure 2B-D). Some areas were observed with loose myxoid or hyaline stroma, in which collagen fibers of different thickness and shape were interspersed among multinucleated giant cells (Figure 2E and F), but no necrosis was observed. Interstitial blood vessels were widely distributed with marked perivascular hyalinization (Figure 2G). Mitotic figures were 2/50 HPF (Figure 2H). In addition, multinucleated giant cells varied in size and shape, with the nuclei mostly nested in the cytoplasm in a wreath-like or lobulated-shape (Figure 2I).
Micrographs showing characteristics of tumor stroma (A) Area showing tumor cells arranged in a wavy pattern (H&E; x40). (B) Area showing apparent myxoid degeneration in the stroma (H&E; x40). (C) Multinucleated giant cells with deep nuclear stains within the pseudovascular space (H&E; x200). (D) Multinucleated giant cells distributed among the spindle tumor cells and the collagenous stroma (H&E; x200).
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In some areas, tumor cells were arranged in a wavy pattern (Figure 3A), the stroma was apparently myxoid (Figure 3B), and showed significant collagenization. Multinucleated giant cells were found in the pseudovascular spaces (Figure 3C) that were also distributed among the spindle-shaped tumor cells (Figure 3D).
Immunohistochemical analysis of the tumor. (A) IHC image showing cells with diffuse CD34 positivity (original magnification x200). (B) IHC staining for BCL-2 showing diffuse membrane and cytoplasm positivity (original magnification x200). (C) Tumor cells showing diffuse membrane positivity for CD99 (original magnification x200). (D) IHC of STAT6 showing partially flaky nuclear positivity (original magnification x200). (E) IHC of CD68 showing partial cytoplasm positivity in giant cells (original magnification x200). (F) IHC for Ki-67 showing some positively stained cells (labeling index of 3%) (original magnification x200).
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IHC revealed cells that were diffusely positive for CD34 (Figure 4A), BCL-2 (Figure 4B), and CD99 (Figure 4C), and negative for S100, SOX10, SMA, EMA, and MUC4 (Table 1), supporting the diagnosis of SFT. Furthermore, nuclear staining for STAT6 by IHC has been shown to be a highly sensitive and specific marker for SFT (Figure 4D). Moreover, IHC for CD68 showed focal cytoplasmic positivity in giant cells (Figure 4E), which is a characteristic of SFT. In addition, only scattered cells were positive for the proliferative marker Ki-67, with a labeling index of 3% (Figure 4F).