PMC4093735_01
(a) Initial CT brain bone window axial cuts showing lesion extending from the inner table to the outer table of the skull vault with fairly well-defined margin, in keeping with sinus pericranii with no other lytic abnormality seen in the skull vault and (b) progression of the lesion 2 years later with increased extent of bony involvement (white arrow)
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F1
The initial impression was that the lump was consistent with sinus pericranii [Figure 1].
Initial MRI brain axial cuts (a) T2 Flair (b) T1-weighted (c) T1-weighted with gadolinium contrast (d) T2-weighted sequences showing an hour glass shaped 2.1 x 1.6 cm T2 isointense enhancing extradural lesion in the right supraventricular parietal cortex with its waist extending through the calvarium, a subgaleal component beneath the skin and an intracranial component indenting the parietal cortex
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F2
It also revealed the previously noted osteolytic lesion involving the right posterior parietal bone, which now had extradural and extracalvarial enhancing soft tissue components [Figure 2].
Follow up MRI brain axial cuts (a) T2 Flair (b) T1-weighted (c) T1-weighted with gadolinium contrast (d) T2-weighted sequences showing significant interval progressive increase in size of the rightparieto-occipital extraaxial dural base enhancing soft-tissue lesion, now measuring approximately 2 x 3.2 x 1.7 cm in maximum orthogonal dimensions. Interval increase in protrusion into the underlying right cerebrum with significant interval development of vasogenic edema in the right parieto-occipital lobe, extending to reach the right atrial subependyma. The lesion is transcalvarial with a subgaleal component, which also showed interval increase in size
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F3
The lesion was transcalvarial with a subgaleal component, which also shows interval increase in size [Figure 3].
Histological images of (a) Pale staining enlarged histiocytes admixed with other inflammatory cells and with foci of emperipolesis (b) S100 immunostainpositive in larger histiocytes (c) CD1a immunostain negative in larger histiocytes
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F4
In the dura, the histiocytic proliferation showed intervening foci of sclerosedstroma [Figure 4].