PMC7568110_01
Axial (a) and 3D volume rendered (b) computerized tomography scan bone window images show a sharp defect in the anterior left parietal bone with beveled edges (arrow). Sagittal postcontrast 3D T1 MPRAGE magnetic resonance imaging (MRI) (c) shows enhancing soft tissue in the scalp and intracranial extra-axial location extending across and filling the calvarial defect (arrow); with extension of enhancing soft tissue into the underlying sulcus (arrowhead). Axial T2W MRI (d) shows that the lesion (arrow) is iso to slightly hypointense to cortex. Axial DWI MRI (e) shows no diffusion restriction within the lesion (arrow). Axial perfusion MRI relative cerebral blood volume (rCBV) image (f) shows reduced rCBV within the lesion (arrow) compared with the adjacent cortex.
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F1
T2W, intermediate signal on T1W MRI, postcontrast enhancement, reduced relative cerebral blood volume (rCBV) on perfusion MRI, and no diffusion restriction [Figure 1]. The primary diagnostic consideration was
(a) Photomicrograph depicting bony trabeculae infiltrated by Rosai-Dorfman disease (hematoxylin and eosin stain x40. (b) High-power view shows histiocytic proliferation along with diffuse lymphoplasmacytic infiltrate. Some histiocytes are large with emperipolesis (red arrows) (hematoxylin and eosin stain x200).
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F2
The diagnosis of cranial RDD was established [Figure 2].
PMC7568110_02
Axial T2W magnetic resonance imaging (MRI) (a) shows a left inferior parietal extra-axial soft-tissue lesion (arrow) with surrounding hyperintense edema. The lesion is hypointense to cortex and there is also a tiny hypointense nodule in the adjacent brain (thick arrow) with intact calvarium. Axial postcontrast TW MRI (b) shows uniform enhancement of the lesion (arrow). Note the contiguous enhancing dural tails (arrowheads) and enhancement of the tiny nodular focus in the adjacent brain (thick arrow). Axial DWI MRI (c) shows no diffusion restriction within the lesion (arrow). Axial perfusion MRI relative cerebral blood volume (rCBV) image (d) shows reduced rCBV within the lesion (arrow) compared with the adjacent brain.
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F3
No bony involvement was seen [Figure 3].
(a) Large histiocytes with abundant pale cytoplasm engulfing intact lymphocytes (red arrows) (hematoxylin and eosin stain x200). (b) Photomicrograph showing inflammatory histiocytic proliferation arising from thick fibrous dura (right upper corner) (hematoxylin and eosin stain x40).
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F4
By immunoperoxidase stains, these were diffusely and strongly positive for S100 antibody, consistent with RDD [Figure 4].
PMC7568110_03
Sagittal postcontrast T1W magnetic resonance imaging (MRI) of the cervicothoracic spine (a) shows a right-sided enhancing epidural soft-tissue lesion (arrow) which appears hypointense on T2W-STIR MRI (b) at C7-T4 spinal canal levels. Axial postcontrast T1W MRI (c) shows extension through the right neural foramen with a sizeable paravertebral soft-tissue component (arrow). Note a tiny enhancing component within the spinal cord parenchyma (arrowhead). Axial T2WI (d) shows hypointensity of the paraspinal lesion and diffuse spinal cord hyperintensity. No vertebral bony involvement is seen.
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F5
There was no significant vertebral bony involvement [Figure 5].
(a) Photomicrograph showing large histiocytes with emperipolesis (red arrow) (hematoxylin and eosin stain x400). (b) The histiocytes show strong diffuse nuclear and cytoplasmic staining for S100 antibody (immunoperoxidase x200).
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F6
The histiocytes were diffusely positive for S100 immunostain, consistent with spinal RDD [Figure 6].
PMC7568110_04
Sagittal postcontrast T1W magnetic resonance imaging (MRI) of the thoracic spine (a) shows an enhancing epidural soft-tissue lesion nearly filling the spinal canal (arrow) with dural tails superiorly and inferiorly, which appears hypointense on T2W (b) and T1W (c) MRI at T4 vertebral level. Axial postcontrast MRI (d) shows severe compression and displacement of the spinal cord to the left anterolateral aspect (arrowhead) by the enhancing lesion (arrow). Axial T2W MRI (e) shows hypointensity of the lesion filling the canal (arrow) and no hyperintense fluid signal of surrounding CSF is seen as it is obliterated. All of the above MR sequences show a slightly T1 and T2 hyperintense, enhancing lesion within the T4 vertebral body (thick arrow), which could introduce the differential diagnosis of vertebral bony and spinal canal metastatic components. Axial bone window computerized tomography scan (f) image, however, clearly shows that the bony lesion is just an incidental vertebral body hemangioma (thick arrow) with characteristic "polka-dot" appearance of its vertical striations.
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F7
However, a correlative CT scan image clearly showed that the bony lesion was an incidental vertebral body hemangioma [Figure 7].
(a) Photomicrograph showing diffuse lymphohistiocytic proliferation in collagenous stroma (hematoxylin and eosin stain x40). (b) High-power view shows histiocytic proliferation along with diffuse lymphoplasmacytic infiltrate. Some histiocytes with engulfed intact lymphocytes are present (blue arrows) (hematoxylin and eosin stain x200).
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F8
Histopathology showed a dura-based lesion composed of histiocytic proliferation with lymphoplasmacytic infiltrate along with lymphophagocytosis, compatible with RDD [Figure 8].
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