PMC8049828_01
(a) Intraoral soft tissue mass in the floor of the mouth from the left ventral tongue surface extending beyond the midline to the right side. (b) Mild submental swelling as a result of an intraoral mass herniation beyond the mylohyoid muscle. (c) Coronal CT section at the level of the first molar in soft tissue window showing a markedly low density and clearly defined margin irregular mass within the left genioglossus muscle extending from ventral tongue to skin overlying the mylohyoid muscle. The density is homogenous and similar to adjacent subcutaneous fat. (d) Midsagittal MRI section in fat suppression showing the hypointense density mass.
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The overlying mucosa was intact and appeared normal (Figures 1(a) and 1(b)). Imaging studies by CT scan and MRI showed an irregular mass in the area of the genioglossus muscle extending from the base of the tongue to the skin overlying the mylohyoid muscle with a density similar to the adjacent subcutaneous fat (Figure 1(c)). A hypointense density mass was observed in fat suppression MRI section at the level of the first molar suggesting an infiltrating intramuscular lipoma (Figure 1(d)).
(a, b) Surgical excision of the intraoral mass. Mass was yellowish, soft, and irregular in shape. Inset in (b) is the whole mass after excision.
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The specimen was formed of lobulated spherical masses, yellowish to pale pinkish in color, and measured 3.5 x 4.7 x 1.5 cm in its greatest dimension (Figures 2(a) and 2(b)).
(a, b) Peripheral and inner areas of the tumor showing thin fibrous tissue capsule with numerous fat lobules and separated with fibrous tissue septae rich in vascular tissue with islands of salivary gland tissue (arrows) within the lipomatous proliferation. Scale bars: 2 mm. (c) Pancytokeratin (AE1/AE3) expression in the ductal and acinar cells in the entrapped salivary gland. The adipose tissue was negative (asterisk). Scale bar: 200 mum. (d) Smooth muscle actin highlighting the myoepithelial cells around the acini and ducts, and the smooth muscle in adjacent vascular structures. Lipomatous elements were negative (asterisk). Scale bar: 200 mum.
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There were entrapped salivary gland acini and ducts scattered within the tumor mass (Figures 3(a) and 3(b)). Proliferative activity as assessed by Ki-67 was less than 1% in both the adipose and salivary gland tissue (Table 1, Figures 3(c) and 3(d)).