PMC6803731_01
(a) Intraoral photograph: a painless submucosal mass in the right buccal region. (b) Doppler ultrasonography of the buccal mass. High blood flow was observed around the nodular mass with low echogenicity. (c) Horizontal CT images. (d) MR images. T1-weighted imaging. (e) Tumor cells were arranged in a patternless manner. Variation in the size and shape of the cells or their nuclei was not conspicuous (FNAB hematoxylin/eosin staining). (f) Tumor cells showed diffuse positivity for CD34 (FNAB IHC) and (g) nuclear positivity for STAT6 (FNAB IHC).
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The mass was well defined with rounded margins and free from skin and muscles (Figure 1(a)). A color Doppler echographic examination indicated high flow velocity of the blood surrounding the mass (Figure 1(b)). A contrast-enhanced image on computed tomography (Figure 1(c)) and contrast-enhanced T1-weighted image on magnetic resonance imaging (Figure 1(d)) displayed 1.5 x 1.5 cm homogeneous enhanced mass in the front of the masseter muscle with a well-defined margin. These spindle cells were arranged and lined in a patternless manner, and variation in the size and shape of the cells or their nuclei was not conspicuous (Figure 1(e)). On immunohistochemistry, the spindle cells were strongly positive for CD34 (Figure 1(f)), STAT6 (Figure 1(g)), and vimentin and negative for EMA, S100, and alpha-SMA.
(a) Gross appearance of the resected specimen. A well-circumscribed nodular mass measuring 15 x 15 x 15 mm with a pale or uniformly white cut surface was observed. (b) The tumor comprised spindle cells with an irregular disposition associated with collagen bands and vascular structures branched with an evident lumen. (c) Tumor cells showed strong positivity for CD34 (IHC). (d) Nuclear positive reaction for STAT6 in spindle tumor cells (IHC).
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Macroscopically, the cut section of the resected specimen showed a circumscribed pale or uniformly white mass measuring 15 x 15 x 15 mm surrounded by a fibrous capsule (Figure 2(a)). Most of the tumor mass consisted of hypocellular areas including ectatic blood vessels (Figure 2(b)). Immunohistochemistry (IHC) demonstrated that the tumor cells were positive for CD34 (Figure 2(c)), STAT6 (Figure 2(d)), vimentin, and Bcl-2 and negative for alpha-SMA, S100, and EMA.