Extradural Glomus Tumor of the Thoracic Spine: Case Report and Literature Review

Objective Glomus tumors are rare lesions that can arise anywhere along the spinal axis. Only thirteen cases have been reported. We report a case of a patient with a rare glomangioma of the thoracic spine. Following a review of the twelve previous cases is a discussion of a spinal glomus tumor with regard to clinical presentation, diagnosis, and treatment. Methods A single, recent case arising from the extradural space of the thoracic spine is described, followed by a literature review of spinal glomus tumors. Results Including our case, thirteen cases of a glomus tumor have been reported. The mean age at the time of diagnosis was 44.6 years (range: 22–73 years) and the male-to-female (M:F) ratio was 1.17:1. The lesion was located in the cervical spine in 1 patient, the thoracic spine in 7 patients, the lumbar spine in 4 patients, and the sacrum in 1 patient. All the tumors were benign; however, there was one report of local recurrence because of incomplete removal. There were no malignant transformations, metastases, or deaths reported with a mean follow-up of 20.09 ± 28.43 months (range: 2–90 months).


Introduction
Spinal masses often present challenging diagnostic and therapeutic scenarios. A recent patient with an extradural mass in the thoracic spine, which was determined to be a glomangioma, illustrates this problem. This case led us to perform a literature review regarding this rare tumor, which we hoped would enable us to determine the tumor's imaging characteristics and biologic behavior, as well as the ability to establish criteria for a preoperative diagnosis. Our analysis of this patient and the current literature are presented.

Materials And Methods
A review of the patient's chart was conducted along with a review of the literature using a Medline search. Translations were performed whenever necessary.
Details of the eight patients (including the current patient) are summarized in Table 1. Case Report was weakening of the myodynamics of both lower extremities. Interestingly, his re exes were symmetric.
The hematologic examination was within normal limits. Magnetic resonance (MR) imaging showed an extradural lesion at the vertebral body of T7, extending to the T9 vertebral body, with low signal intensity on T1-weighted images (T1WIs); in addition, bright enhancement occurred following gadolinium administration (Fig. 1). The lesion showed high signal intensity on T2-weighted images (T2WIs). The spinal cord was severely compressed, and the T8 neural foramen was enlarged. However, osseous destruction was not observed.
Surgical intervention was proposed because of the progression of the neurologic de cit. The patient underwent a T8-T9 hemilaminectomy and complete resection of the extradural tumor. The tumor had an irregular capsule, and slight bleeding occurred when it was incised. After undergoing posterior decompression, his sensory de cit was stable; however, he had regained normal strength in both legs and was living independently.

Histopathologic Examination
Permanent microscopic slides showed a hypercellular neoplasm with sheets of round-to-polygonal epithelioid cells. Individual nuclei were regular, round-toovoid, and lacked signi cant nuclear atypia or necrosis. The background stroma was hyalinized to a myxoid appearance. Scattered, dilated, capillary-sized vascular channels coursed through the lesion (Fig. 2). The neoplastic cells were immune-negative for CD117, CK, CgA, Desmin, Factor , LCA, E-cadherin, NSE, Syn, and S-100. Immunoreactivity to SMA, vimentin, CD34, PAS, and CD99 ( Fig. 3) was noted. This staining pattern, in conjunction with the histological features, was consistent with the diagnosis of a glomangioma. This case is considered to be the second with these characteristics to be reported in the literature.
At his 3-month follow-up examination, the patient stated that he had fully recovered and had no di culty in walking. He had returned to work and was very satis ed with the results of his surgery.

Results
A Medline search of the literature found 12 cases of a spinal glomus tumor. The details of those patients and our case are summarized in Table 1.
The mean age at the time of diagnosis was 44 .6 years (range: 22-73 years) and the male-to-female (M:F) ratio was 1.17:1.The lesion was located in the cervical spine in 1 patient, the thoracic spine in 7 patients, the lumbar spine in 4 patients, and the sacrum in 1 patient. All the patients underwent posterior decompression and one patient underwent emergency embolization of the segmental arteries (adhesive and coil embolization) because of profuse bleeding that could not be controlled with other measures. All 13 lesions were located in the extradural space of the spine. The dura was not involved in any case; however, bone structure involvement, erosion, and lytic lesions were found in 8 of 13 patients.
There were postoperative follow-ups with 11 of the 13 patients from the literature review, as well as our patient; the mean follow-up of the 13 patients was 20.09 ± 28.43 months (range: 2-90 months). The longest follow-up was 7.5 years. One case of local recurrence was found in the literature review. This was due to incomplete removal. No malignant transformations, metastases. or deaths occurred at the conclusion of the follow-up periods.

Discussion
Glomangiomas, a subset of glomus tumors that have a rich vascular network, are neoplasms of the glomus apparatus. Glomus tumors are benign neoplasms of the perivasculature. They arise from modi ed smooth muscle cells called glomus cells; they are located in the walls of the Sucquet-Hoyer canal, which is a specialized arterial-venous anastomosis central that controls blood ow for thermal regulation.
Microscopically, glomus tumors present as uniformly round-to-ovoid glomus cells arranged as lobules, strands, or broad sheets in a brickwork-like manner. The association with vascular structures includes indistinct capillaries in the walls of the surrounding large blood vessels as well as highly altered vessels. Uniform epithelioid glomus cells with inconspicuous-to-well-de ned nucleoli are found between the sinusoidal vessels. Despite their epithelioid appearance and intimate association with vasculature, glomus cells are immunoreactive with vimentin and SMA. However, a small number of these tumors may coexpress myogenic markers and CD34. The current case was immunoreactive with SMA, Vimentin, CD34, PAS, and CD99.
Irrespective of their anatomical location, glomus tumors are usually benign; however, rare malignant cases have been described [29,30]. Recently, Folpe et al. [31] proposed a classi cation of atypical and malignant glomus tumors. Malignant glomus tumors are de ned as tumors with: (1) large size (> 2 cm) and deep location, (2) atypical mitotic gures, or (3) nuclear atypia. In contrast, glomus tumors of uncertain malignant potential are super cial in location and show a high mitotic activity, are large in size, or are deeply located. However, in their series of unusual glomus tumors, Folpe et al. [31] de ned the tumor location as either super cial to the peripheral soft tissue or deep to it. In their study, there were 9 deeply located peripheral soft tissue glomus tumors, and all of them were larger than 2 cm; however, only 5 cases metastasized. In a series of 32 gastrointestinal glomus tumors, which by de nition were deeply located, only 1 case metastasized, although 19 were larger than 2 cm [32]. In our case review, all of the lesions were > 2cm, and deeply located. The mean follow-up of 13 patients together with the current patient was 20.09 ± 28.43 months (range: 2-90 months); the longest follow-up was 7.5 years. No malignancies had appeared by the conclusion of the follow-up periods. Therefore, the risk of metastases of the deep-seated glomus tumors to the peripheral soft tissue appears to be markedly different from those located in other deep regions. An extracutaneous, deep location should not be considered to be a sign of malignancy. On the basis of these criteria and the lack of atypical mitotic gures, our patient's tumor would be classi ed as benign. Occasionally, glomus tumors occur in a hereditary manner. The gene has been localized to chromosome 1p21-1p22, which codes for glomulin, a protein thought to play a role in vascularization [33,34].
The preoperative diagnosis of spinal glomus tumor is very di cult. Usually, the plain radiograph is unremarkable for a spinal glomus tumor. Most patients with a spinal mass undergo a CT scan and magnetic resonance imaging (MRI). Although CT images can show well-de ned lesions in a few cases, MR images are considered to be an excellent diagnostic modality. On T1-weighted MR images, glomus tumors may present as a sharply marginated lesion with hypointensity or isointensity, while on T2WIs they are mostly hyperintense. Furthermore, they usually show strong intense enhancement on T1WIs after intravenous administration of gadolinium-DTPA [4]. Most glomus tumors are surrounded by an envelope. T2WI and T1WI after intravenous administration of contrast medium can detect the envelope as a low signal intensity rim. The envelope, which may be incomplete, may be the consequence of a secondary reaction with the surrounding tissue. An envelope-like structure was observed in our case. The MR images of our case are fairly similar to the MR features of the other seven cases. However, a characteristic nding in our case was signal-void stular lesion in the tumor. The features of the stular lesion were similar to the images of vascular structures. It also was comparable to the histological ndings of tissue with a prominent vascular component. The stular lesion, due to the direction of ow, was identi ed on the sagittal images but not on the axial images.
In our case, the differential diagnosis included primary extradural masses or intradural, extramedullary lesions of the spine. Schwannomas, which are the most common extradural tumors, show the typical dumbbell-shaped appearance (extra-and intra-dural portions) in 50% of cases; however, 50% are completely extradural. Schwannomas on MRI images tend to have low signal intensity on T1WI and have brightly increased signal intensity on T2WI due to the high-water content of these lesions. These lesions usually were markedly enhanced following gadolinium administration. The MR ndings of the eight cases had similar MR features of the schwannomas, except for the signal-void stular lesion. Ganglioneuromas and neuroblastomas are tumors of childhood, which often appear with large paraspinal tumor masses.
Choice of therapeutic strategy is predicated according to lesion location and clinical presentation. An overwhelming majority of glomus tumors are benign and are cured by simple local excision. The postsurgical recurrence rate is approximately 10%, because of incomplete removal. In the literature we reviewed, with the longest follow-up being 7.5 years, there was one report of local recurrence because of incomplete removal; however, no malignant transformations, metastases, or deaths occurred by the conclusion of the follow-up period.

Conclusions
In summary, spinal glomus tumor, although rare, deserve consideration during the differential diagnosis of spinal lesions. Preoperative diagnosis is di cult; however, certain imaging features can give more information to base this diagnosis on, and raise its level of certainty. Differentiation of glomus tumor from schwannomas can be accomplished on the basis of histology and immunostaining. An overwhelming majority of glomus tumors are benign and are cured by simple local excision.

Declarations
Ethics approval and consent to participate Both ethics approval and consent to participate in this case report have been given prior to this publication.

Consent for publication
Consent for publication has been given by the person/patient in this case report. A copy can be seen on request at any time.

Availability of data and materials
Not applicable

Competing interests
The authors declare that they have no competing interests.

Funding
This study was funded by "The Science Project of Liaoning Province" (2018225094).