PMC6220415_01
Swelling on the right side of the neck below the angle of mandible.
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fig1
It was noncompressible and nonpulsatile (Figure 1).
CECT neck shows cystic lesion medial to sternocleidomastoid muscle and inferomedial to parotid gland (arrows showing edge of the tumor). Eccentric solid area shows minimal enhancement on contrast administration.
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Contrast-enhanced computed tomography (CECT) of the neck was performed which showed a solitary, relatively well-defined predominantly cystic lesion measuring 3.8 x 3.7 x 3.9 cm with smooth margins and minimally enhancing eccentric solid areas in the right side of the neck inferomedial to parotid gland located between sternocleidomastoid muscle laterally and carotid space medially (Figure 2).
(a) T2-weighted magnetic resonance imaging shows hyperintense fluid-fluid level and isointense eccentric solid area (arrows showing edge of the tumor). (b) T1-weighted magnetic resonance imaging shows hyperintense fluid-fluid level (arrows showing edge of the tumor).
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T1- and T2-weighted images suggesting hemorrhagic or proteinaceous component. The eccentric solid component was heterogenous and isointense on T2-weighted images (Figures 3(a) and 3(b)).
Well-circumscribed tumor with smooth surface.
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Histological examination revealed a globular solid-cystic mass of size 4.5 x 3.5 x 2.5 cm (Figure 4).
(a) Tumor cells are arranged in storiform pattern and as short fascicles. Tumor cells are intermixed with scattered lymphocytes (hematoxylin and eosin; magnification, 200x). (b) Tumor cells are oval to elongated with indistinct cytoplasmic border and ovoid nucleus with few of them showing prominent nucleoli (hematoxylin and eosin; magnification, 400x).
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Microscopically, tumor was composed of ovoid to spindle-shaped cells arranged in sheets and focal storiform pattern (Figure 5(a)). Individual tumor cells had vesicular nucleus with diffuse fine chromatin (Figure 5(b)).
(a) Tumor cells show strong membranous staining for CD23 (magnification, 400x). (b) Tumor cells show positive staining for CD35 (magnification, 400x). (c) Tumor cells show weak membranous staining for CD21 (magnification, 400x). (d) Tumor cells show negative staining for panCK (magnification, 400x). (e) Tumor has a low mitotic activity of 4-5% (magnification, 400x).
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Immunohistochemical analysis showed positive staining for CD23 (Figure 6(a)), CD35 (Figure 6(b)), and vimentin. Tumor cells showed weak staining for CD21 (Figure 6(c)) and negative staining for pan-cytokeratin (panCK) (Figure 6(d)), leukocyte common antigen (LCA), epithelial membrane antigen (EMA), and smooth muscle actin (SMA). Ki67 index was 4-5% (Figure 6(e)).