PMC7186469_01
Preoperative and postoperative imaging features of the patient. T2-weighted MRI axial (A) and coronal (B) images show a solid tumor arising from the trigeminal nerve (red arrow) with heterogeneous contrast-enhanced (C); (D-H) Axial MRI images reveal gradual enlargement of the tumor; (I) Destruction of the adjacent skull base bone is shown in the oval; (J) Postoperative CT shows subtotal removal of the tumor; (K,L) Follow-up CT scanned 3 weeks after surgery shows tumor recurrence.
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Initial magnetic resonance imaging (MRI) of the brain demonstrated a 3.0 x 2.0 cm solid mass originated from the right trigeminal nerve, with heterogeneous contrast enhancement (Figures 1A-C), which was believed to be a trigeminal schwannoma despite less typical imaging features. A brain MRI a month later showed slightly enlargement of the tumor (Figure 1D), ~4.2 x 2.3 cm in size. The young man was conscious of the partial alleviation of the above-mentioned symptoms after radiotherapy, while the rescanned MRI (Figure 1E) showed further enlargement of tumor size apart from radiation-induced edema. Emergences of new clinical symptoms, such as right-side hearing loss and ptosis, developed in this male patient in the following 2 months, with tumor extension toward the right cerebellopontine angle (6.3 x 3.2 cm), pushing the brainstem and cerebellum, as well as destruction of the adjacent bones (Figures 1F-I). There was no significant hemorrhage in the operative field according to the postoperative computed tomography (CT) carried out the next day (Figure 1J). Unexpectedly, a brain CT scan 3 weeks after surgery showed an obvious increase in tumor size (Figures 1K-L).
Hematoxylin-eosin and immunohistochemical staining of the tumor tissue. (A) Histological staining shows a high cell density with eosinophilic cytoplasm and prominent nucleolus; (B-F) Positive expression of EMA, VIM, CD99, synaptophysin, and BRG1, respectively; (G,H) Negative expression of desmin and INI-1 (at 200 magnification).
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Parts of the tumor cell appeared with a high nucleocytoplasmic ratio and presented with a blue small cell-like appearance (Figure 2A). Immunohistochemical (IHC) staining revealed partial immunoreactivity for epithelial membrane antigen (EMA), vimentin (VIM), CD99, synaptophysin, smooth-muscle actin (SMA), and brahma-related gene 1 (BRG1, also known as SMARCA4), while desmin, S100, and glial fibrillary acidic protein (GFAP) were negatively expressed in the tumor specimen (Figures 2B-G). Unexpectedly, loss of expression of the INI-1 protein was discovered in tumor cells (Figure 2H).