Two plexiform schwannoma of phrenic neurogenesis could be resected en bloc by surgery.
Central Message.
Two phrenic neurogenesis plexiform schwannoma were successfully treated by ingenuity for surgery. A surgical approach that can be combined with palpation to ensure that no lesion remains is useful.
In the thoracic cavity, neurogenic tumors are most commonly found in the posterior mediastinum, and most are solitary. Schwannoma is the most common neurogenic tumor and has multiple variants. The plexiform type is the rarest variant, with high potential for recurrence, unlike other variants. Plexiform schwannomas rarely occur in deep soft tissues or internal organs.1 We report a case of resection of schwannomatosis including plexiform schwannoma of phrenic nerve development; to our knowledge, no similar case has been reported thus far. The institutional review board of Seirei Mikatahara General Hospital approved the publication of the data (approval number: 22-57, approval date: January 10, 2023). The patient provided informed written consent for the publication of the study data.
Case Report
The patient was a 47-year-old woman with a history of surgery for left phrenic neurogenic solitary schwannoma localized on the left side of the heart 20 years previously who suffered from left phrenic nerve palsy. Computed tomography incidentally revealed multinodular lesions extending from her left neck to the anterior mediastinum (region A) and on the left side of the heart (region B). In addition, a 12-mm solitary nodule in contact with the left first rib (region C) was observed (Figure 1). Thoracoscopic resection of region C was performed to establish a definitive diagnosis to determine the treatment strategy. A diagnosis of benign schwannoma was made, and complete resection of the residual lesion was planned at a later date.
Figure 1.
Imaging findings at the first visit to our department. Computed tomography showed an elevated left diaphragm and a multinodular lesion from the left neck to the anterior mediastinum (blue arrow) and on the left side of the heart (red arrow). In addition, a solitary nodule adjacent to the left first rib was observed (arrowhead).
We performed surgery with a small thoracotomy with the assistance of a thoracoscope for region B (Video 1) and a transmanubrial approach that not only a simple cervical incision but also a left anterior thoracotomy along the upper edge of the second rib was added to cut the manubrium for region A (Video 2). The 2 regions were continuous via a normal phrenic nerve. Many of the very small nodules were located a small distance from the nerve and difficult to see with the naked eye, so palpation was useful to identify any minimal remaining nodules. It was possible to remove all lesions as a group by dissecting the phrenic nerve at a normal site near its root. Microscopically, the resected tumors had regions predominantly consisting of the Antoni A region with a palisade arrangement of cell nuclei and formation of Verocay bodies. The Antoni B region was occasionally observed, but mitosis was rarely seen (Figure 2). These findings confirmed 2 plexiform schwannomas of the left phrenic neurogenesis (region A and B) and a solitary schwannoma of the left first intercostal neurogenesis (region C), leading to the diagnosis of schwannomatosis.
Figure 2.
Microscopically, the resected tumors had regions predominantly consisting of hypercellular areas consisting of fascicular and intertwined growths of spindle-shaped cells with indistinct cytoplasmic borders (Antoni A region). In these regions, the cell nuclei were arranged in a palisade and formed Verocay bodies. Occasional hypocellular regions with loose stroma (Antoni B region) were also observed, but mitosis was rarely seen (hematoxylin–eosin staining, original magnification ×20).
After surgery, the patient recovered well and was discharged from our hospital on postoperative day 8. At the time of writing, only a few months have passed since the operation; however, her condition is good without signs of recurrence, new lesions, or complications.
Discussion
Plexiform schwannoma is the rarest variant, accounting for only 5% of all schwannomas. It has a high local recurrence rate (up to 50%), but it does not appear to have malignant or metastatic potential.1 Pathologically, it shows the same characteristics as conventional schwannomas. In the pathology literature, “plexiform” is often synonymous with “macroscopically multinodular lesion.”2 There are also minute nodules that are only visible microscopically.1
Schwannoma is usually solitary, but multiple schwannomas can occur in the same or multiple nerves, called schwannomatosis. It is recognized in only approximately 10% of multiple nerve tumors, with an annual incidence of 0.58 cases per 1,000,000.3 Although approximately 5% of plexiform schwannomas are associated with schwannomatosis or type 2 neurofibromatosis,1 there are no reported cases of schwannomatosis involving phrenic schwannoma. Thus, our case is extremely rare.
Complete resection of both the tumor and adjacent nerve fibers is recommended for plexiform schwannoma because of its high recurrence rate.4 Nerve paralysis is unavoidable because of transection of the involuntary nerve, so a wait-and-see approach should be considered if there are no symptoms and the size is stable. However, if resection is performed, en bloc resection should still be considered to avoid multiple surgeries for recurrence. In this case, the lesions could be completely resected together because phrenic nerve palsy had already occurred before surgery, and it was clearly progressive. Plexiform schwannoma has many very fine nodules, so palpation is useful for accurately determining whether there are any residual lesions.
Conclusions
This case is considered to be highly suggestive. Although extremely rare, it is highly suggestive that plexiform schwannoma may also appear in the thoracic cavity. In addition, by our presenting rare preoperative imaging findings, readers can assume this disease exists. It is also suggestive that palpation is very useful and important during surgery. This case demonstrates that new lesions can continue to form from nerves throughout the body. It is not clear how long follow-up should be continued; however, careful follow-up is required in the future.
Acknowledgments
We thank Japan Medical Communication for editing the manuscript.
Footnotes
Disclosures: The authors reported no conflicts of interest.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
Supplementary Data
The VATS approach was used to confirm that the cervical mediastinal lesions and the left cardiac lesions were continuous via a normal phrenic nerve. Palpation was useful for evaluation of residual lesions. Video available at: https://www.jtcvs.org/article/S2666-2507(23)00059-7/fulltext.
The TMA approach was used to dissect the normal phrenic nerve more proximal to the most central lesion. Palpation was also useful for evaluation of residual lesions. Video available at: https://www.jtcvs.org/article/S2666-2507(23)00059-7/fulltext.
References
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Associated Data
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Supplementary Materials
The VATS approach was used to confirm that the cervical mediastinal lesions and the left cardiac lesions were continuous via a normal phrenic nerve. Palpation was useful for evaluation of residual lesions. Video available at: https://www.jtcvs.org/article/S2666-2507(23)00059-7/fulltext.
The TMA approach was used to dissect the normal phrenic nerve more proximal to the most central lesion. Palpation was also useful for evaluation of residual lesions. Video available at: https://www.jtcvs.org/article/S2666-2507(23)00059-7/fulltext.