PMC9479567_01
Axial T2-weighted magnetic resonance imaging performed near the same level, at the initial presentation to a local physician (a) and 6 weeks later (b), showing an emergence of a tumor in the right calvarial convexity (b, arrow).
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F1
Cerebral magnetic resonance imaging (MRI) at the time did not reveal any abnormal findings in the intracranial cavity, skull, or scalp [Figure 1a]. As the headache persisted, the patient underwent a second MRI after 6 weeks, which revealed a mass lesion in the right calvarial convexity [Figure 1b].
Axial (a) and coronal (c) computed tomography scans and their corresponding bone target images (b and d) showing an isodense mass in the right parietal bone (a and c, arrowhead) accompanied by irregularly shaped bone erosion mainly involving the diploe and outer table (b and d, arrow). The inner table is partially erosive (d, arrow). Dashed arrow: coronal suture.
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F2
The inner table was partially erosive [Figure 2].
Axial T1- (a) and T2- (b) weighted magnetic resonance imaging showing a calvarial tumor presenting iso/low intensity on T1- and high intensity on T2-weighted images, and well demarcated from the surrounding tissue (arrow). Post contrast axial (c) and coronal (d) T1-weighted magnetic resonance imaging showing heterogeneous enhancement of the tumor with the inner part adjacent to the dura mater (arrow). Note that the temporalis muscle and subcutaneous tissue adjacent to the tumor are extensively swollen and enhanced compared to those on the contralateral side.
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F3
The inner part of the tumor appeared adjacent to the dura mater [Figure 3].
(a-d) Intraoperative photos. (a and b) Reflection of the scalp flap showing a whitish tumor protruding through the completely eroded outer table (arrow). The tumor is partially adhered to the inner surface of the temporalis muscle (a, asterisk). (c) En bloc tumor resection has been achieved with surrounding bone. (d) Fine defects are found in the inner table adjacent to the tumor (arrow). A: Anterior, I: inferior, IS: inner surface of the skull, OS: outer surface of the skull, P: posterior, S: superior, TM: temporalis muscle, Arrow in (c): bone defect, 25 x 20 mm in diameter at the outer surface of skull; Asterisk: tumor tissue adhered to the temporalis muscle fibers.
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F4
The size of the bone defect was 25 x 20 mm at the outer surface of the skull [Figure 4].
(a) Photomicrograph of the resected specimen showing proliferation of neoplastic cells with cleaved nuclei (arrows) accompanied by infiltration of the lymphocytes (dashed arrows) and eosinophils (arrowheads). Immunohistochemical examination showing positive staining for the S100 protein (b) and CD68 (c). Tumor invasion of the subcutaneous tissue is observed (d, arrows). SCT: Subcutaneous tissue. (a and d): hematoxylin and eosin stain. (a): x 200, (d): x 40, and (b and c): x 200.
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F5
Immunohistochemical examination showed positive staining for the S100 protein and CD68 [Figure 5].