PMC6968711_01
Preoperative physical examination. The swelling was elastic and hard. There was no scar and no central punctum.
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Preoperative MRI findings. (a) MRI (T1-weighed image): the mass was slightly hyperintense compared to the muscle and pushing outward against the extensor tendons (arrows). (b) MRI (T2-weighed image): the mass was slightly hyperintense compared to the muscle (arrows).
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It showed a slightly high intensity on both T1-weighted and T2-weighed images and was pushing out the extensor tendons (Figure 2).
Intraoperative photograph (arrow: antebrachial interosseous membrane). The cystic mass was covered by a thick white capsule and its bottom was adjacent to the antebrachial interosseous membrane. There was no scarring around the fascia.
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It was covered with a thick white capsule and its bottom was adjacent to the antebrachial interosseous membrane (Figure 3).
Histopathological findings (hematoxylin-eosin staining, original magnification x 100) upper arrow: squamous epithelium lining, lower arrow: keratin collections. The cyst wall was composed of stratified squamous epithelium with abundant keratin. There were no hair tissue structures or atypical cells.
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The definite diagnosis was epidermoid cyst without malignancy (Figure 4).