2.2 Histopathology examination
Grossly the tumor tissue appeared as soft, solitary, encapsulated with well-defined surface and had a yellowish color. Microscopically-well circumscribed tumor composed of spindle shaped cells arranged in a palisading fashion. There was no mitotic activity or malignancy features were seen. Immunostaining demonstrated strong extensive S-100 immunoreactivity of the nodules with CD34, Desmin, SMA, and EMA negativity (Fig. 5). These findings confirmed the diagnosis of Schwannomas.
2.3 Follow-up and outcomes
Postoperatively, there were no motor or sensory deficits. No infection was found after surgery. One week after the surgery, the patient was able to perform full motion of his operated hand. Symptoms of pain and paraesthesias resolved, and his finger range of motion recovered to the normal level. Tinel-Hoffman sign was negative. The patient was followed up by clinic every 3 months. Two years after the surgery, the patient had not experienced tumor recurrence.
Schwannomas are typically benign slow growing nerve sheath tumors, which usually arise on the flexor aspect of the extremities. Generally, they present as solitary tumors, although there are reports of patients with multiple tumors in the literature. In material presented by Ogose et al, the incidence of multiple schwannomas had been reported as 4.6% of all patients diagnosed with schwannoma. The case we reported showed multiple localized schwannomas confined to three different nerves in one hand. To our knowledge, it is extremely rare in the literature.
Pain and swelling are the usual presentation in general clinical physical examination. The similar features sharing with other soft tissue tumors cause difficulties in diagnosis. Schwannoma may be misdiagnosed as neurofibroma, lipoma and ganglion preoperatively.[6,7] Schwannoma can arise in association with any peripheral nerve but it generally arises in the sensory portion of the nerve. Neurological symptoms like pain, paraethesia and numbness are presented when the tumors compress the involved nerve.[8,9] On clinical exam, the swelling can be mobile from side to side, but not in the longitudinal axis of the nerve. Percussion induces painful paraesthesiae in the area of the nerve of origin similar to Tinel sign. A full history and careful detailed examination can improve the preoperative diagnostic accuracy. In our case, symptoms such as palpable tumor mass, pain, paraesthesias, and positive Tinel-Hoffman sign enhanced the evidence to diagnosis schwannomas.
USG and MRI are potent for localizing the tumors in hand as they are noninvasive and easy to manipulate. Ultrasonography works as a first-line imaging examination to localize and evaluate lesions of the hand. Schwannoma is homogenous, hypoechoic mass which exhibit enhanced through transmission, target appearance, pseudocystic appearance on ultrasonography, which is rather similar to ganglion cysts.[11,12] Therefore, schwannoma of the hand is hard to distinguish from a cystic lesion. Till now, MRI is still the most competent imaging modality used to localize the tumors and to plan for surgery. Schwannoma on MRI is revealed by high signal intensity on T2 scans and low signal intensity on T1 scans. Possibly, it can lead to misdiagnosis as nerve sheath tumors and ganglions that have same appearance with Schwannoma on MRI. However, we can identify schwannomas from ganglions through the administration of gadolinium in which ganglions do not show any enhancement. In addition, the location of the lump to the nerve is another key to separate them, where schwannomas is eccentric to the nerve while neurofibromas is central to the nerve.
Histology of schwannoma shows the typical features including areas of Antoni type A, which characterized as compact bundles of Schwann cells, or Antoni type B, difined as loose matrix of oval cells. Both of the 2 types and a distinct capsule could be seen in our case. Compared with neurofibromas, schwannomas shows greater cellularity in Antoni type A. The cellular areas of the schwannomas express positive S-100 protein strongly, while neurofibromas express variable S-100 protein. It is also a key characteristic to distinguish schwannomas from leiomyosarcoma and fibrosarcoma.
Surgery is the main therapeutic strategy for schwannoma, the principle of which is enucleation of tumor with no nerve damage. Proper microsurgical dissection is as important for success as in a bloodless surgery, such utilization of loupe or microscopical magnification is strongly advised to use in order to avoid the nerve fibers damage. It requires surgeons pay meticulous attention to preserve functionally important sensory and motor branches without making unnecessary sacrifice. To protect the nerve, we used surgical loupes to remove the schwannomas in our case, and ultimately no nerve damage was found. Successful treatment of multiple schwannomas depends upon accurate early diagnosis. Surgery can improve the treatment outcome of multiple schwannomas.
First and foremost, I would like to show my deepest gratitude to my colleagues Dr Hui Lu and Dr Hui Shen who have provided me with valuable assist in every stage of writing this paper. Last but not least, I’ d like to thank all my friends, especially my lovely wife for her encouragement and support.
Data curation: Shuai Jiang, Hui Shen.
Funding acquisition: Hui Lu, Shuai Jiang.
Methodology: Hui Shen.
Writing – original draft: Shuai Jiang.
Writing – review & editing: Shuai Jiang, Hui Lu.
Shuai Jiang orcid: 0000-0002-4401-6595.
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Keywords:Copyright © 2019 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
histopathology; MRI; multiple schwannomas; surgery