Background

Schwannoma, also known as perineural fibroblastoma, neuroma, or neurilemmoma, is a slow growing benign tumor which arises from any nerve coated with a Schwann cell whether it is spinal, cranial, or autonomic nervous system. One of 4 cases of schwannomas occurs in the cervico-facial region with 1 to 12% of all schwannomas develop in the oral cavity mainly in the tongue [1]. It mainly affects the second and third decade and can be life-threatening if it becomes large [1]. Developing in youth is unusual [2].

We report a case of tongue base schwannoma in a teenager and discuss possible differential diagnoses, the specificity of pathology examination, and management techniques.

Case presentation

A 16-year-old male patient with no significant medical history is presented to the outpatient clinic for 3 months’ history of a firm swelling at his tongue base associated to a voice change with no other symptoms such as dyspnea, odynophagia, dysphagia, or sleep apnea. Oral cavity examination showed a 4×2 cm masse on the left posterior lateral side of the tongue, with normal-appearing overlying mucosa. This mass comes in contact with the left palato-glossal arch. No cervical lymph nodes were found. The remaining clinical examination was unremarkable. Magnetic resonance imaging (MRI) revealed a rounded shape well circumscribed mass of richly vascularized tissue measuring 3cm in long axis in the left postero-lateral side of the tongue, protruding at the level of the oropharynx (Figs. 1, 2, and 3). The patient underwent a transoral removal of the mass under general anesthesia. Perioperative findings disclosed a submucosal well-encapsulated mass with no significant vascularization (Figs. 4 and 5). The mass was completely removed through a transoral approach with cold instrument dissection and control of the tumor’s unique posterior pedicle by hemostatic forceps and surgical thread ligation. The excised mass measured 4×2 cm, had a smooth surface, white color and round shape borders. The postoperative course was uneventful, the patient did not report any significant pain or discomfort, breathing was normal, and oral feeding was allowed at J1 postoperatively. The patient was discharged from the hospital at J2 postoperatively. Microscopically, the lesion was characterized by a blending of cellular and acellular areas with the presence of Verocay bodies. Immunohistochemistry was positive for S-100 protein, confirming the diagnosis of schwannoma. The patient was first seen 1 month after surgery. He did not report any abnormal event or sensation or swallowing disorders. The patient remains asymptomatic for 6-month follow-up with no evidence of disease recurrence. Patient’s care episodes’ timeline is reported in Fig. 6.

Fig. 1
figure 1

MRI T2 sagittal view showing a well circumscribed hyper-intense tongue base mass (arrow)

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Fig. 2
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MRI T2 coronal view showing a submucosal hyper-intense heterogeneous tongue base mass (arrow)

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Fig. 3
figure 3

MRI T2 axial view showing a submucosal hyper-intense heterogeneous tongue base mass with close contact with the lingual tonsil (star)

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Fig. 4
figure 4

Per-operative view of transoral resection of the tongue base submucosal mass (star) throw a lateral incision (arrow)

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Fig. 5
figure 5

The surgical specimen presented as submucosal well-encapsulated firm white mass

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Fig. 6
figure 6

The patient’s episodes of care timeline

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Table 1 displays clinical, surgical techniques, and follow-up of our case and other schwannoma cases reported in literature

Table 1 Comparison table with previously reported cases of tongue schwannoma
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Discussion

Schwannoma is a benign nerve sheath tumor that mainly occurs in youth. However, all ages can be affected [1]. Male and female are approximately affected similarly [2]. The etiology of schwannomas is unknown. One quarter to half of all schwannomas cases occur in cervico-facial region. Vestibulo-cochlear nerve is the commonly most affected in head and neck region especially in neurofibromatosis [17]. In the oral cavity, schwannoma is rare (1 to 12%) [18]. Intraoral schwannomas mainly arise from the tongue, followed by the palate, mouth floor, gingiva, lip, and vestibule [18]. Usually, it presents as a painless mass in any part of the tongue of less than 2 cm. However, when the mass grows over 3 cm, compression symptoms may occur such as dysphagia, odynophagia, or swallowing discomfort, altered voice. Dyspnea is a warning manifestation that make surgical management urgent [3].

The differential diagnosis for lingual schwannoma may include neurofibroma, lingual thyroid lipoma, lymphangioma, leiomyoma, and benign salivary gland tumors [19]. However, malignant tumors such as liposarcomas, lymphoma, or carcinoma should be kept in mind. Nevertheless, malignant tumors are unlikely to present a slow growth course as typically schwannoma does. Malignant transformation of schwannoma is exceptional and mainly happens in “ancient” schwannoma according to Ackerman and Taylor [20] or in case of neurofibromatosis [2].

Imaging techniques include ultrasound scanning, CT scan, and MRI. Most schwannomas are shown at no contrast CT scan as a well-circumscribed homogeneous soft-tissue masses. MRI is the imaging modality of choice for showing the exact extent of the tumor. Therefore, it should be performed at the first place before tongue base schwannoma. MRI shows the tumor as a well circumscribed mass isointense to muscle on T1-weighted images and homogeneously hyperintense on T2-weighted images [19]. However, tumor necrosis due to the mass volume or its transformation may alter those radiologic characteristics, as in our case, the mass exhibited a hypointense T1 area of necrosis.

The exact diagnosis are suggested by fine needle aspiration biopsy, which is not always practicable, and confirmed by pathology examination [4].

Histologically, schwannomas are composed of two prototypes of cell organization called Antoni A and Antoni B. The Antoni A region is a hypercellular zone with fusiform cells that have nuclei arranged in palisade forming parallel rows and producing the Verocay bodies. The Antoni B region is a hypocellular with a loose myxoid stroma that might exhibit degenerative features, such as cysts, calcifications, hemorrhages, hyalinization, and inflammatory infiltrate. It is not common for these degenerative aspects to evolve into malignant sarcomas with invasive behaviors and metastatic potential [21]. Immunohistochemistry shows that schwannoma cells tongue exhibits strong and diffuse nuclear and cytoplasmic S-100 protein expression and extensive nuclear SOX10. Other cellular markers associated with neuronal tumors are might be present such as E.N.E., vimentin, glycoprotein, SMA, desmin, and dimentin [21].

Complete surgical excision is the main treatment modality. The transoral approach remains the most used. Other approaches were reported such as submandibular, suprahyoid pharyngotomy, trans-hyoid, and lip split approach [2]. Besides surgical approach, tongue base schwannoma presents another challenge regarding securing airways before surgery. Intubation might require the use of fibroscope or videolaryngoscope, but most importantly the hands of an experienced anesthesiologist. However, in some cases, transient tracheotomy might be performed.

Conclusion

Oral cavity schwannoma is rare, and the prevailing oral location is the tongue. This particular site holds many risks related to impact symptoms or to anesthesia and securing airways. We performed a trans-oral resection of a tongue base schwannoma using cold instrument. As the tumor is well encapsulated, this approach seems convenient and less invasive for complete surgical excision.