Schwannoma of Left Chest Wall: a Case Report and Literature Review

Background: Schwannoma of chest wall is rare intercostal nerve tumor originated from Schwann cells. Here, we present a rare case about schwannoma was misdiagnosed as solitary broma by preoperative biopsy. We intend to improve clinicians' understanding of the disease by discussing the clinical manifestations, diagnostic points and differential diagnosis of patients with thoracic wall schwannoma. Case presentation: A 38-year-old male presented with "left chest pain for more than 1 month". Enhanced Computer Tomography(CT) can of the lung revealed space occupying lesions in the left lower posterior chest wall. Preoperative biopsy was solitary broma. After the improvement of preoperative preparation, the patients were given surgical treatment, postoperative pathology showed: schwannoma of chest wall. Chest pain improved after operation. The patients were followed up for 8 months. Discussion and Conclusions: Schwannoma, especially in the chest wall, is rare, with atypical clinical symptoms, single imaging manifestations, high variable rate of puncture pathology, and easy to be misdiagnosed. Complete surgical resection of tumor is the main treatment, and no new adjuvant / adjuvant therapy has been reported yet.


Background
Thoracic wall schwannoma is a rare intercostal nerve tumor originated from intercostal Schwann cells.
We reported a case of solitary broma highly suspected by preoperative enhanced CT and con rmed by preoperative biopsy, but diagnosed as schwannoma of chest wall by postoperative pathology in Department of thoracic surgery, The First Bethune Hospital of Jilin University.
This case reports the thoracic wall schwannoma was misdiagnosed as solitary broma with progressive chest pain and successfully treated with minimally invasive video-assisted thoracoscopic surgery.

Case Presentation
A 38-year-old male with left chest pain for one month was admitted to Beijing chest hospital on June 20, 2020. Lung CT showed that the left lower posterior thoracic cavity space occupying lesion, adjacent ribs were involved, which was larger than one year ago, the lesion may origin from pleural or neurogenic lesions. Then the patient underwent percutaneous tumor puncture in Beijing hospital on July 10, 2020.
Deny the history of hypertension, diabetes, heart disease, family history and tuberculosis history. A systemic physical examination was unremarkable. Auxiliary inspections including blood routine, urine routine, coagulation routine, liver function, renal function, ion, Erythrocyte sedimentation rate (ESR), tumor markers were normal, tuberculosis antibody, sputum smear and t-spot were negative. A chest enhanced CT demonstrated massive high-density shadow protruding into the thoracic cavity was seen on the left lower posterior chest wall, with the size of about 7.4cm * 5.2cm * 5.5cm, regular shape, smooth edge, and wide base connected with the left pleura. The arterial phase: 23HU, venous phase: 30HU, with small vascular shadow in it, considering solitary broma; there was no obvious enlarged lymph node shadow in mediastinum ( Figure 1). Figure 1D is the three-dimensional reconstruction gure of chest wall mass based on chest CT images, after preoperative preparation was improved, the operation was started. The anesthesia of double lumen endotracheal intubation came into effect, a tumor with the size of 7cm * 6cm * 6cm was found between the 7th and 8th ribs of the left chest wall under three dimensional (3D) video-assisted thoracoscopy. Then the tumor was completely removed ( Figure 2). Intraoperative rapid pathology reported: interlobar tumor of chest wall. Postoperative histopathological analysis showed that the tumor is consistent with schwannoma ( Figure 3), on immunohistochemistry, S-100 protein and Vimentin are positive ( Figure 4).
The patient recovered well after operation, discharged 5 days after operation, followed up by telephone 8 months after operation, the patient's chest pain relived, and life as usual.

Discussion And Conclusions
Primary chest wall benign tumor is not common, patients often were found with chest wall tumor because of persistent chest wall pain(1). Chest wall schwannoma, which is seldom seen, originates from Schwann cells of the nerve sheath (2). It is a lobulated or spherical solitary, encapsulated tumor that grows slowly in the retromediastinal pleural cavity (3,4). Schwannoma accounts for about 5% of all benign soft tissue tumors; it is most common in spinal cord and nerve root, protruding from paravertebral to mediastinum, and rarely in chest wall. The incidence rate is almost no gender difference, almost between 20 years old and 30 years old. Pain and nervous system symptoms are almost absent in small tumors (<5cm)(5, 6).
Isolated bromas are mainly derived from a CD34 positive dendritic mesenchymal cell and belong to a kind of interlobular tumor(7), differentiating into myo broblasts and broblasts is characteristic of isolated broma. Solitary broma is rare, most of them are benign, about 12% -20% of them have local recurrence, distant metastasis and other malignant changes after several years of stability, and eventually lead to death(8, 9). The main age of onset was 60 to 70 years old (10). Incidence rate of male and female was similar (11).
Neurilemmoma and solitary broma grow slowly and most of them are asymptomatic. They are only found when the tumor growth oppresses the surrounding tissue and produces pain, cough and other symptoms. It is di cult to distinguish them by clinical symptoms (Table 1), CT showed they are clear and homogeneous soft tissue tumors (11)(12)(13).
Pathologically, schwannoma was composed of Antoni type A and Antoni type B. the tumor was encapsulated without axons, and there might be blood vessels in the tumor, the speci c immunohistochemical features of schwannoma including S-100 protein, vimentin and enolase were positive, while neuro lament protein was negative (10,14,15). In particular, S-100 protein can be seen in almost all schwannomas and is a marker of benign schwannomas (15,16). Solitary broma presented as spindle cell tumor pathologically (17), immunohistochemical features were positive for CD34,vimentin, B cell lymphoma-2(bcl-2) or CD99 (10,11,18), vimentin is a marker of mesenchymal cells, while CD34 as the most consistent conventional marker, is a transmembrane glycoprotein that widely exists in dendritic mesenchymal cells and participates in antigen presentation (11,18). Recent oncological studies indicate that activator of transcription 6 (STAT 6) antibody is an immunohistochemical marker for solitary broma (19). However, keratin, Desmin, S-100 protein, carcinoembryonic antigen, α 1-ACT and F-VIII related antigen were negative (18,20).
The patient's clinical symptoms have no obvious characteristics, imaging studies are di cult to differentiate from other tumors, and puncture pathology shows that CD34 and vimentin are positive, suggesting that they are derived from mesenchymal cells. The puncture tissue is small and can't show the whole picture of the tumor, and there are differences in tumor cells. Therefore, it is misdiagnosed as solitary neuro broma before operation. Because of the similar imaging ndings and not prominent clinical manifestations, it is a great challenge to differentiate schwannoma from solitary broma. Key points of differentiation between schwannoma and solitary broma are listed in Table 1.

Consent for publication
Informed consent was obtained from the patient.

Availability of data and materials
All data generated or analysed during this study are included in this published article.

Competing interests
The Authors declare that there are no con icts of interest.

Funding
Funding information is not available.

Authors' contributions
Author Youbin Cui is the main performers of the operation, author Tianyu Lu and Ze Tang are assistants in the surgery, author Yue Yang and Da Qin are in charge of the postoperative recovery of patients, author Congcong Li and Ze Tang are responsible for article writing and image procession.

Figure 1
Chest enhanced CT. Figure 1A-1C chest enhanced CT showed the tumor (narrow) of the left inferior posterior wall protrudes into the thoracic cavity with regular shape and smooth edge. The broad base is connected with the left pleura, and the shadow of small blood vessels can be seen in it. Figure 1D threedimensional reconstruction gure of chest wall mass based on chest CT images.

Figure 2
Gross specimen exhibits the size of the chest wall tumor is about 7.4cm* 5.2cm * 5.5cm, which is tough and has smooth diolame.
Page 10/11 Figure 3 H&E staining demonstrates the cell morphology was consistent with that of schwann. Figure 4