|Year : 2017 | Volume
| Issue : 1 | Page : 36-38
A rare case of primary benign schwannoma of the pleura
Department of Radiology, St. John's Medical College, Bengaluru, Karnataka, India
|Date of Web Publication||19-Jun-2017|
St. John's Medical College, Bengaluru - 560 034, Karnataka
Source of Support: None, Conflict of Interest: None
Schwannoma, also called neurilemmoma, is a benign peripheral nerve sheath tumor. Most common locations are flexor surfaces of the extremities, neck, mediastinum, retroperitoneum, posterior spinal roots, and cerebellopontine angle. Pleural schwannomas are extremely rare neoplasms of the thoracic cavity. To the best of our knowledge, till date, <20 cases have been reported. Herein, we report a case of primary benign pleural schwannoma in an elderly 60-year-old female in whom the pleural mass was discovered incidentally on computed tomography chest. The patient was subjected to left posterolateral thoracotomy; pleural mass was resected which showed histopathological and immunohistochemical features of schwannoma.
Keywords: Histopathology, imaging, pleura, schwannoma, thoracic cavity
|How to cite this article:|
Ravikanth R. A rare case of primary benign schwannoma of the pleura. Digit Med 2017;3:36-8
| Introduction|| |
Schwannoma is an encapsulated benign peripheral nerve sheath tumor which is almost always solitary. Common locations are the flexor surfaces of the extremities, neck, mediastinum, retroperitoneum, posterior spinal roots, and cerebellopontine angle. Pleural schwannomas are rare and arise from the autonomic nerve fiber sheaths in the pleura. They are generally benign, asymptomatic, slow-growing lesions, and occur more commonly in adults with a male predominance. Histopathological differential diagnosis includes neurofibroma and other benign spindle cell tumors such as leiomyoma, leiomyosarcoma, and calcifying aponeurotic fibroma which may also show palisading of the nuclei. Histopathological variants of this lesion are ancient schwannoma, benign myxoid schwannoma, benign epithelioid schwannoma, benign glandular schwannoma, and psammomatous melanotic schwannoma.
| Case Report|| |
A 60-year-old woman presented with respiratory symptoms due to acute exacerbation of asthma. The patient is a known seasonal asthmatic for 10 years. Physical examination revealed bilateral wheeze. All routine laboratory investigations were within normal limits. Computed tomography (CT) scan chest showed evidence of well-defined, cystic mass with partial peripheral enhancement measuring 6 cm × 4 cm involving the left side of posterior mediastinum. No pleural effusion/thickening observed [Figure 1]. A radiological diagnosis of “posterior mediastinal cystic mass-neurofibroma” was considered. The patient was posted for surgery and a left posterolateral thoracotomy was done. A mass was seen arising posteriorly from the pleura, measuring 7 cm × 5 cm, which was predominantly cystic. R0 excision of pleural mass was done corresponding to resection for cure or complete remission and specimen sent for histopathological examination. Gross examination of the specimen revealed gray-white solid and membranous soft tissue bits partly cystic, showing mucoid and hemorrhagic areas. Microscopic sections studied from the specimen revealed a well-encapsulated mass showing benign spindle cells with alternating hypercellular Antoni A areas with nuclear palisading with Verocay bodies formation and hypocellular Antoni B areas showing myxoid changes and thick-walled blood vessels with perivascular hyalinization. No mitosis or necrosis was noted. A provisional diagnosis of schwannoma was considered. Immunohistochemistry (IHC) stain S-100 performed showed diffuse and strong positivity of tumor cells. Based on histopathology and IHC, a final diagnosis of primary pleural benign peripheral nerve sheath tumor consistent with schwannoma was made. The patient had an uneventful postoperative recovery with no adjuvant therapy. Postoperative investigations included a contrast-enhanced CT (CECT) thorax, which showed no residual tumor/collections. Six months later, the patient was completely asymptomatic, and follow-up of CECT thorax showed no evidence of tumor recurrence.
|Figure 1: Axial contrast-enhanced computed tomography image of the chest demonstrating a left-sided posterior mediastinal cystic mass lesion (star) showing peripheral enhancement (arrow)|
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| Discussion|| |
Primary pleural schwannomas are exceedingly rare neoplasms. They account for 1%–2% of all thoracic tumors. Although it can occur at any age, pleural schwannomas commonly affect adults between their third and sixth decades. In addition, males are more commonly affected than females. Majority of pleural schwannoma are benign though malignancy has been reported in some cases. Schwannomas arise from specialized myelin-producing cells - Schwann cells, of either the sympathetic or parasympathetic autonomic nerve fiber sheaths. Schwannomas arising in the pleural surface of the lung generally grow slowly; hence, they do not usually produce symptoms. The majority of patients with pleural schwannomas are often asymptomatic or may present with nonspecific and vague symptoms. Therefore, the vast majority of pleural schwannomas are discovered incidentally during investigations for other complaints.
Although they are rarely encountered, malignant pleural schwannomas have been reported in literature. Malignant lesions have been described in patients with neurofibromatosis Type 1 and patients with positive history of previous radiation therapy. In addition, malignant pleural schwannomas are likely to produce symptoms due to their large size compared to benign lesions. Large tumors have the potential to produce pain and neurological symptoms due to their mass occupying effect and compression on adjacent structures. Diagnosing pleural schwannomas is often challenging. Definitive diagnosis cannot be reached even with advanced imaging modalities and laboratory investigations.
Radiological images aid in raising the suspicion about the nature of the lesion and narrowing the differential diagnosis. Pleural schwannomas should be included in the differential diagnosis of solitary, solid, well-demarcated pleural lesions, which include, but are not restricted to, pleural lipomas, pleural metastasis, mesotheliomas, and solitary fibrous tumors. Moreover, laboratory tests usually lie within normal limits. Therefore, definitive diagnosis can only be established through histopathological examination and IHC staining of the neoplasm, which requires a section of the tumor. CT scan remains the diagnostic imaging modality of choice for these neoplasms. CT scan can outline the size, number, and exact location of the lesions. CT scan can also demonstrate cystic and/or solid components of the tumor. Malignant pleural schwannomas have similar features on CT scan; however, they are usually associated with the presence of pleural nodules, pleural effusions, and metastatic pulmonary nodules. Microscopically, Antoni A and Antoni B areas are revealed in the majority of pleural schwannoma cases. Antoni A represents areas of hypercellularity with Verocay bodies. Antoni B areas of myxoid hypocellularity exhibit degenerating changes (i.e., cyst formation, hemorrhage, calcification, xanthomatous infiltration, and hyalinization). Immunohistochemically, pleural schwannomas typically stain diffusely and strongly positive for S-100 protein.
| Conclusion|| |
Pleural schwannomas are extremely rare neoplasms of the thoracic cavity. Imaging and histopathological examinations are necessary to diagnose pleural schwannomas. The standard care of the management of pleural schwannomas is primarily surgical resection thoracoscopically or complete pleural resection of the tumor whenever technically possible with frequent continuous follow-up.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
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