PMC4983411_01
Lateral X-ray of the skull shows an extensive osseous lesion of the diploe with periosteal new bone formation (arrows) along the external table of the anterior skull
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Fig1
Plain x-ray films revealed a large, sclerotic lesion involving the right side of the frontal bone of the skull, extending to the unilateral frontal sinus (Fig. 1).
a CT axial image shows a primarily sclerotic lesion involving the diploe (white arrow) extending across the midline (black arrow). b There is a polypoid mass in the right frontal sinus (asterisk). c Sagittal reconstruction shows the lesion (white arrows) and the polypoid mass (asterisk)
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Fig2
Further imaging with CT scan showed a diffuse sclerotic right-sided frontal lesion measuring approximately 9.5 x 12 x 1.5 cm involving the diploe with extensive mature periosteal new bone formation along the external table of the right frontal bone (Fig. 2a-c).
a Axial T1-weighted MR image shows thickening of the right frontal part of the diploe (arrows) with an underlying extensive low signal osseous lesion. b Axial T1-weighted MR image post gadolinium shows minimal enhancement of the periosteal part of the lesion (arrows). There is no evidence of abnormality related to the brain parenchyma
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Fig3
An MRI scan confirmed the osseous nature of the tumour and the absence of infiltration of the brain parenchyma (Fig. 3a, b).
Histopathological features of PIM showing a extensive organised reactive bone formation within the lesion. Intertrabecular fibrous tissue contains b a proliferation of cells with spindle-shaped and vesicular nuclei; c scattered meningotheliomatous whorled collections of cells; d occasional cells with clear, vacuolated cytoplasm
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Fig4
There was abundant thickened organised reactive woven and lamellar bone with numerous thickened bone trabeculae separated by dense collagenous fibrous tissue containing scattered cells with wavy, spindle-shaped or ovoid vesicular nuclei between bone trabeculae and in Haversian channels (Fig. 4a, b). There were also numerous scattered cells with vacuolated cytoplasm and focally small meningotheliomatous whorls of cells with vesicular nuclei in fat and fibrous tissue (Fig. 4c, d).
Immunohistochemistry of PIM showing lesional cell expression of a EMA in fibrotic areas and b EMA and c PR in meningotheliomatous areas
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Fig5
Immunohistochemistry showed that the lesional cells strongly expressed epithelial membrane antigen (EMA), vimentin and progesterone receptor (PR) (Fig. 5a-c).