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Facial nerve schwannomas are benign, encapsulated, slow-growing tumors arising from Schwann cells of seventh cranial nerve, rarely found in the parotid gland. Clinical diagnosis is usually difficult because other unilateral parotid tumors, such as the pleomorphic adenoma, Warthin’s tumor or mucoepidermoid carcinoma, occur as an asymptomatic slow-growing mass. This report describes a case of a 76-year-old female affected by asymptomatic intraparotid facial nerve schwannoma. Morphological characteristics, clinical course, radiographic and histopathological features, and surgical therapy are discussed.
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A rare case of intraparotid facial nerve schwannoma
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A rare case of intraparotid facial nerve schwannoma
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                                                                                                      Case report



    A rare case of intraparotid facial nerve schwannoma




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    Claudio Ungari1 MD, PhD                                schwannomas arises from the neural structures of the
    Matteo Gualtieri1 MD                                   head and neck, and thus also the facial nerve (CN
    Emiliano Riccardi1 MD                                  VII) can be affected (1).




                                                                                          io
    Fabio Filiaci1 MD                                      Facial nerve schwannomas (FNS) mostly (90%) af-
    Bruna Cerbelli2 MD                                     fect the intracranial and intratemporal course of the
                                                           nerve and more rarely (9%) involve the intraparotid




                                                                     az
                                                           area, accounting for 0.2 to 1.5% of all parotid gland
    1 Oral and Maxillo Facial Sciences Department,         tumors (1-5). Out of a total of 3722 patients with
    “Sapienza” University of Rome, Rome, Italy             schwannoma retrospectively reviewed over 38-year
    2 Department of Radiological, Oncological and Patho-   period by Caughey et al., only 29 were related to fa-




                                                                   rn
    logical Sciences, Policlinico Umberto I, “Sapienza”    cial nerve and only 8 involved the parotid segment of
    University of Rome, Rome, Italy                        the facial nerve (4).
                                                           Intraparotid FSN usually appears as asyntomatic,
                                                           painless, slow-growing mass, even if facial nerve dys-




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    Corresponding Author:                                  function, hemifacial paresis or paralysis can be pre-
    Matteo Gualtieri                                       sent.
    Department of Odontostomatology and Maxillofacial      The lack of clinical and radiographic pathognomonic
    Surgery, Policlinico Umberto I
                                                  In       features makes difficult to diagnose the tumor preop-
    “Sapienza” University of Rome                          eratively. The definitive diagnosis is exclusively based
    Via Lorenzo il Magnifico 110                           on histopathological and immunohistochemical exam-
    00162 Rome, Italy                                      inations (5).
    Tel.: +39 3288750884                                   This report describes a case of a 76-year-old female
                           ni

                                                           affected by intraparotid facial nerve schwannoma of
                                                           the right parotid gland.
    Summary
                         io


    Facial nerve schwannomas are benign, encapsu-          Case report
    lated, slow-growing tumors arising from Schwann
                       iz



    cells of seventh cranial nerve, rarely found in the    A 76-year-old female was referred to the Department
    parotid gland. Clinical diagnosis is usually diffi-    of Maxillofacial Surgery of “Policlinico Umberto I”
    cult because other unilateral parotid tumors, such     (“Sapienza” University of Rome) for evaluation of a
          Ed




    as the pleomorphic adenoma, Warthin’s tumor or         slow-growing and painless swelling in the right preau-
    mucoepidermoid carcinoma, occur as an asymp-           ricular area, present since 10 months, without any
    tomatic slow-growing mass.                             symptoms of facial weakness, twitching or numbness.
    This report describes a case of a 76-year-old fe-      Medical history and general physical examination
    male affected by asymptomatic intraparotid facial      were non-contributory. Extraoral examination re-
    nerve schwannoma.                                      vealed a swelling approximately 5x4 cm in size, local-
 IC




    Morphological characteristics, clinical course, ra-    ized in the right parotid gland. The mass had a soft
    diographic and histopathological features, and         consistency and was non-tender to palpation. The fa-
    surgical therapy are discussed.                        cial nerve functioning evaluation was regular. No cer-
                                                           vical adenopathy was evident.
C




    Key Words: Schwann cells, facial nerve, parotid        Ultrasonografy (US) showed a 48x33x31 mm sized,
    gland, neoplasm, schwannoma.                           well defined, oval, anechoic mass in the superficial
                                                           lobe of the right parotid gland. The anechoic signal
                                                           was evocative of fluid component. Color Doppler ex-
©




                                                           amination didn’t detect any vascular structure.
    Introduction                                           Fine-needle aspiration cytology (FNAC) was incon-
                                                           clusive and reported “grouping of blood cells and lym-
    Schwannomas (also named neurilemmomas) are un-         phocytes. Negative research for neoplastic cells”.
    common, benign, slow-growing tumors that originate     Magnetic resonance imaging (MRI) revealed a homo-
    from Schwann cells of myelinated peripheral or cra-    geneous lesion 45x35 mm in size, involving the su-
    nial nerves (1, 2). Approximately 25-40% of all        perficial lobe of right parotid gland. The mass was

    130                                                                      Annali di Stomatologia 2018;IX (3):130-133
    A rare case of intraparotid facial nerve schwannoma




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    Figure 1. MRI showed a homogeneous mass into the right parotid gland superficial lobe. The mass was characterized by a
                                                          In
    hypointense signal in T1- weighted images (A) and hyperintense signal in long TR-weighted images with a peripheral en-
    hancement (B).



    characterized by a hypointense signal in T1-weighted         ing encapsulated tumors with a neuroectodermal ori-
                               ni

    images and hyperintense signal in long TR- weighted          gin, which may arise from the nerve sheath of any
    images with a peripheral enhancement (Fig. 1).               cranial or peripheral nerves (1, 2).
    Surgical exploration was planned under general               FNS originate from Schwann cells along the course
                             io


    anesthesia. Intraoperatively, the facial nerve branch-       of seventh cranial nerve and most of them arise from
    es were identified and carefully isolated from the yel-      the intracranial course of the nerve, while they were
    low encapsulated mass (Fig. 2), which was localized          rarely seen in the parotid gland (2).
                           iz



    deep into the parotid superficial lobe. The tumor was        Intraparotid FNS affects more frequently the fifth and
    excised along with the superficial lobe of the parotid       sixth decade of life and no clear sex predilection was
    gland, preserving facial nerve fibers. The frozen sec-       reported (2). The tumor usually presents as solitary,
           Ed




    tion examination was not performed because the               unilateral, slow-growing, painless and mobile mass.
    nerve was not adherent to the tumor and the dissec-          The facial nerve function is generally unaffected, be-
    tion was possible.                                           cause the eccentric growth of the tumor tends to
    The immediate postoperative was uneventful and fa-           move away the nerve fibers (1). The incidence of in-
    cial nerve functions were preserved. No adverse ef-          traparotid facial nerve partial palsy is low (20-27%)
    fects or recurrence were reported at 6-month follow-         (1).
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    up.                                                          Intraparotid FNS is a diagnostic challenge due to
    Histological examination (Fig. 3) showed an encapsu-         non-specific findings of some diagnostic modality,
    lated mass, characterized by areas of hypercellularity       such as FNAC, which is usually inconclusive as in our
    with occasional nuclear palisading (Antoni A pattern)        case, US showing an anechoic mass and computer-
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    and hypocellular zones of indistinct cytoplasm and           ized tomography, in which soft tissue structures and
    hyperchromatic nuclei (Antoni B pattern). Immunohis-         the facial nerve are not well visualized (1, 2, 5-9).
    tochemistry confirmed the diagnosis of schwannoma,           The most appropriate exam to determine schwanno-
    showing diffuse and intense S100 protein immunore-           ma along the course of the facial nerve is MRI with
©




    activity of neoplastic cells.                                gadolinium, although the same findings may be found
                                                                 in other neurogenic tumors (1, 2, 8, 9). In MRI FNS
                                                                 appears as well-circumscribed lesion characterized
    Discussion                                                   by a hypointense signal in T1-weighted images and
                                                                 hyperintense signal T2- weighted images. The target
    Schwannomas (or neurilemmomas), first described              sign is central low and peripheral higher signal inten-
    by Virchow in 1908, are rare, benign and slow-grow-          sity on T2 sections (1, 2, 5-9).


    Annali di Stomatologia 2018;IX (3):130-133                                                                        131
    M. Gualtieri et al.


                                                                                                 Figure 2. Intraoperative view of
                                                                                                 the yellow encapsulated tumor
                                                                                                 mass, localized deep into the
                                                                                                 parotid superficial lobe.




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    Figure 3. Histopathological and immunohistochemical findings: A) in the histological exam hypercellular areas consisting of
    spindle cells arranged in short, interlacing fascicles (Antoni A) were alternated with hypocellular areas (Antoni B). Neoplastic
    cells were characterized by hyperchromatic nuclei and indistinct cytoplasmic borders. Nuclear whorling and palisading (Ve-
    rocay bodies) were present (Hematoxylin and eosin, original magnification, 4X); B) in the immunohistochemical exam
 IC




    widespread and intense S100 protein immunoreactivity of neoplastic cells were observed (S100 immunostaining, original
    magnification, 2X).
C




    Histopathologically, intraparotid FNS is a well-encap-            Facial nerve fibers are not involved in the tumor
    sulated mass lesion, composed by elongated nucle-                 mass, which tends to push away the nerve axons,
    ate spindle cells arranged in two types of patterns,              due its origin from the Schwann sheath.
    which are usually present in different proportions in             Immunohistochemical profile is essential to establish
©




    the same tumor (2, 3, 5). In the Antoni A pattern cells           the origin of the tumor: positive immunostaining for S-
    and cytoplasmic processes are arranged in hypercel-               100 confirms the diagnosis of schwannoma and neg-
    lular areas with little stromal matrix and their nuclei           ative smooth muscle antigen (SMA) stain rules out
    often lying in parallel rows or in a palisading arrange-          leiomyoma (1, 2, 5, 11). Intraoperative frozen section
    ment (Verocay body). In the hypocellular Antoni B                 examination may also be useful in order to make di-
    pattern irregular cells with no nuclei definable pal-             agnosis and exclude malignancy (1, 10).
    isading are scattered in a loose connective tissue.               In the management of intraparotid schwannoma two

    132                                                                                   Annali di Stomatologia 2018;IX (3):130-133
    A rare case of intraparotid facial nerve schwannoma


    different approaches have been reported in the litera-      any public or private organizations.
    ture (1, 2, 5, 8, 10-13). Conservative surveillance is
    advocated in patients with minimal or absent facial         Funding
    nerve dysfunction or tumor localized to the parotid
    gland without intratemporal extension, due to the           This research did not receive any specific grant from




                                                                                                            li
    slow and indolent growth of the tumor and the risk of       funding agencies in the public, commercial, or not-for-
    nerve damage (2). Instead, surgical approach is rec-        profit sectors.




                                                                                                          na
    ommended and considered the gold standard treat-
    ment, because in same cases complete tumor exci-
    sion with nerve preservation is technically possible        Conflict of interest
    and leads to cure (1, 2, 5, 10-13).
    In 2007 Marchioni et al. proposed a classification of       The Authors declare that there are no conflicts of in-




                                                                                                        io
    intraparotid FNS into four types, based on the mass         terest in regard to this work.
    extent and involvement of the facial nerve, in order to
    evaluate whether the tumor resection should involve




                                                                             az
    or not the nerve (3). In type A the facial nerve is pre-    References
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    mediate reconstruction with a nerve graft or neuror-              Schwannoma of Parotid Gland: Difficulties in Diagnosis and




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                                                                      Eur Arch Otorhinolaryngol. 2009;266:475-479.
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C
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    Annali di Stomatologia 2018;IX (3):130-133                                                                                      133
