An unusual case of vulvar schwannoma
© Park et al.; licensee BioMed Central. 2015
Received: 7 September 2014
Accepted: 23 March 2015
Published: 8 April 2015
Schwannoma is a benign, solitary, slow-growing neoplasm of the peripheral nerve sheath. These tumors are rarely found in the external genital system, and only a few cases of vulvar schwannoma have been reported. Herein, we report a case of a vulvar schwannoma. A 37-year-old woman presented with a 3-cm-sized painless mass of the vulva which had been present for 3 years. Magnetic resonance imaging (MRI) of the pelvis showed an isolated finding of a 4.6-cm-sized round mass with a well-defined margin in the midline vulvar area. Simple excision of the tumor was undertaken, and histological examination with immunohistochemical testing demonstrated a vulvar schwannoma. Although benign schwannoma only rarely occurs in the vulva and other external areas of female genitalias, we suggest that it should be considered a differential diagnosis for patients that present a vulvar enlargement or mass. Simple surgical resection and follow-up is the most convenient treatment.
Schwannoma (also known as neurilemmoma) is generally a benign, solitary, nodular tumor of a peripheral nerve sheath. It can occur sporadically or in patients with neurofibromatosis. Its most common locations are in the head, neck, upper and lower extremities, posterior mediastinum, and retroperitoneum . However, it is rarely found in the external female genitalia. According to our best knowledge, few cases of vulvar schwannomas have been reported in the literature. We describe a case of benign vulvar schwannoma and review of the literature.
Schwannoma is a benign peripheral nerve sheath tumor, arising from Schwann cells in the myelin sheath of the peripheral nerves. Schwannoma is solitary, encapsulated, slow-growing tumor which is characteristically painless . It is most frequently located in the head, neck, trunk, upper and lower extremities, posterior mediastinum, and retroperitoneum [2,3]. These tumors are rarely found in areas of the female genital system such as the clitoris, vulva, ovary, cervix, and round ligament, with less than ten case reports of schwannoma involving the vulva. The age range varies from 5 to 84 years, occurring most commonly in the age group of 20 to 40 [4,5]. Clinical symptoms may vary depending on which nerve is affected. But mostly, painless, immobile, and non-tender mass lesions are observed. Vulvar schwannomas are rarely multifocal . They are usually benign and malignant schwannomas of external female genitalia are extremely rare, with less than 1% becoming malignant [7,8]. Differential diagnoses include Bartholin’s cyst, labial cyst, and mesenchymal tumors such as lipoma, liposarcoma, fibrosarcoma, and angiosarcoma . The pre-operative diagnosis of a vulvar neoplasm is difficult; thus, biopsy may be required to exclude the possibility of malignancy and to decide upon an appropriate treatment. Also, radiologic imaging studies are important for characterization and differentiation between a benign and malignant vulvar mass. Vulvar schwannomas have previously been misdiagnosed as malignant tumors such as neurosarcoma, neurofibrosarcoma, and the malignant schwannoma . Microscopic observation with HE staining can reveal the characteristic histologic appearance that can confirm accurate diagnosis. Histologically, the hallmark of schwannomas is a pattern of alternating Antoni type A and Antoni type B areas. Antoni type A tissue is composed of a tightly packed sheath of spindle cells arranged in palisade and swirling patterns. Antoni type B tissue is composed of loosely packed spindle cells and cells with small round nuclei. They also exhibit cystic degeneration, with Verocay bodies occurring as the tumor enlarges. Also, typical schwannoma features such as nuclear palisading and Verocay body-like structures occur without mitosis. A schwannoma must be distinguished from a neurofibroma, which is another benign tumor of the peripheral nerves with different histopathological characteristics. Microscopically, the presence of encapsulation, two types of Antoni areas, and diffusely strong immunostaining for S-100 protein distinguish schwannoma from neurofibromas . The conventional variant is the most common type of vulvar schwannoma, but plexiform and ancient variant types also have been reported [2,9,12]. The most accurate diagnosis can be established through an immunohistochemical examination. A strong positive stain for S-100 protein appears in benign schwannomas. The malignant schwannomas are thought to be composed of dedifferentiated Schwann cells that had somewhat lost their capacity to synthesize S-100 protein . The treatment of choice for benign schwannomas is complete excision, and prognosis is generally excellent following the operation. However, a relapse has been reported, which appears to have been a result of incomplete resection in a huge-sized schwannoma . In our case, the mass was completely removed and to date, the patient is well, with no recurrence. Although benign schwannoma only rarely occurs in the vulva and other external areas of female genitalia, we suggest that it should be considered as a differential diagnosis for patients presented with vulvar tumors.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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