PMC7749957_01
The first magnetic resonance imaging (MRI) of November 2018 (a - T1 axial and b - sagittal scans) showed a homogeneous lesion (arrow) of 12 x 13 mm at the fibula's head level. The second MRI in axial (c) scan, performed after oxygen-ozone therapy, documented a slight increase of the tumor size. It is evident a change in tumor intensity, which had become inhomogeneous, and with a rim of contrast enhancement (d).
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F1
A first MRI [Figure 1a and b] was, therefore, performed in November 2018, depicting a homogeneous lesion of about 12 x 13 mm at the branching point between the left common peroneal and sural nerves. A second MRI [Figure 1c and d] with contrast medium showed an increase of tumor's dimensions (14 x 16 mm) and, noticeably, also a change in tumor morphology: It had become heterogeneous, with a rim of contrast enhancement and a hypointense central core.
Intraoperative photographs under microscopic view: in (a), the schwannoma is visible between common peroneal nerve and sural nerve. After the YELLOW560 filter activation, the tumor showed a fluorescein uptake more intense than the surrounding nerves (b). The capsule (arrow in c) appeared extremely thick and adherent to the tumor and the originating nerve, requiring multiple manipulations for intraneural dissection and schwannoma removal (d-f).
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F2
These factors determined the impossibility to remove the tumor en block; it was instead removed through a gentle piecemeal resection [Figure 2].
The histological examination revealed (a) a nerve sheath tumor constituted by well-differentiated Schwann cells, characterized by nuclear palisades consistent with Verocay bodies (H and E, x40). The microscopic study at x100 highlighted foci of foreign body reaction (H and E in b) with uniformly sized, grey-yellowish microspheres phagocytized by multinucleated giant cells (immunostained with CD68 in c).
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F3
Histological examination [Figure 3] revealed a nerve sheath tumor constituted by well-differentiated Schwann cells, with a thin capsule, loose Antoni B, and compact Antoni A areas, characterized by nuclear palisades consistent with Verocay bodies.