Brain stem angioleiomyoma mimicking meningioma: a case report

Introduction

Angioleiomyoma is a benign lesion of mesenchymal origin, which always occurs in the uterine system (1). Pathologically, angioleiomyoma is composed of well-differentiated smooth muscle cells with few mitotic features. However, primary intracranial angioleiomyoma is a very rare condition (2-4), commonly reported in immunocompromised patients, such as those with Epstein-Barr virus infection (5). Since the first reported case by Lach et al. in 1994, only over 60 cases have been reported in the literature (6). Here, we reported a case of intracranial angioleiomyoma, mimicking meningioma in pre-operative magnetic resonance imaging (MRI) images, which make the differential diagnosis difficult before surgery. Currently, the optimal therapy for primary intracranial angioleiomyoma is surgical resection, and adjuvant radiation therapy for the residual tumor. We present this case in accordance with the CARE reporting checklist (available at https://tcr.amegroups.com/article/view/10.21037/tcr-24-151/rc).

Case presentation

The whole process of this case is described in Figure 1. The patient was a 42-year-old male, presented with dizziness and unsteady walking for about six months, without symptoms of cranial nerve deficit. Head computer tomography (CT) scan showed a well-defined lesion adjacent to the right brain stem with high intensity (Figure 2). Contrast brain MRI exhibited an extra axial mass with homogeneous enhancement located at the edge of the right tentorium, sticking to the right pontine, mimicking meningioma as showed in MRI images (Figure 2). However, the differential diagnosis should include either lymphoma or metastasis. Chest and abdomen CT scans of the patient revealed no other lesions. The human immunodeficiency virus (HIV) status of the patient was negative, and the patient was also not taking immunosuppressive medication.

Figure 1 Timeline figure describing the whole process of the case. CT, computer tomography; MRI, magnetic resonance imaging.

Figure 2 Radiological features of the presented case of angioleiomyoma. (A) Head CT scan showed a well-defined lesion adjacent to right brain stem with high intensity (as the white arrow showed); (B) in T1-weighted MRI, the lesion showed hypointense signal (as the white arrow marked); (C) in T2-weighted MRI, the lesion exhibited hyperintense signal (as the white arrow marked); (D-E) contrast brain MRI demonstrated that the lesion was homogeneously enhanced, located at the edge of right tentorium, stick to right pontine, mimicking meningioma (as the white arrows marked); (F) post-operative head CT showed no bleeding or swelling inside the brain. CT, computer tomography; MRI, magnetic resonance imaging.

Surgical resection

The patient underwent a minimally invasive keyhole microsurgery via sub-temporal approach. After retracting the temporal lobe and cutting the tentorium, it was found that the tumor was stuck to the right pontine. The trochlear nerve and posterior cerebral artery were first separated, then the tumor was completely resected without injury of brain stem. After the surgery, the patient did not develop new neurological deficits and head CT showed no bleeding or swelling inside the brain (Figure 2). The patient recovered quickly from the surgery, and was discharged 1 week after surgery. Six-months follow-up brain MRI showed no residual tumor (Figure 3).

Figure 3 Follow-up brain MRI showed no relapse of the lesion (as white arrows marked). MRI, magnetic resonance imaging.

Pathological analysis

Hematoxylin-eosin (H&E) staining demonstrated bundles of bland, well-differentiated smooth muscle cells and intervening variably sized blood vessels in the grey red mass, and mitotic figures were absent. Immunocytochemistry analysis showed that the tumor cells were diffusely positive for smooth muscle actin (SMA) and Vimentin. The endothelial component was uniformly stained by CD34. Desmin expression was focally positive. HMB45 stain was negative. Overall, the appearance was consistent with angioleiomyoma (Figure 4).

Figure 4 Pathological analysis of angioleiomyoma of the presented case. (A) Spindle shaped cells with blunt ends and few mitotic figures were found by H&E staining, and cavernous type tumor is composed of dilated vascular channels with proliferation of smooth muscle bundles in the intervascular spaces (×100); (B-D) immunocytochemistry showed the tumor cells were positive for SMA, CD34 and Desmin (×100). SMA, smooth muscle actin.

All procedures performed in this study were in accordance with Huashan Hospital Ethics Committee and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Angioleiomyoma is a benign smooth muscle cell tumor commonly occurring in the uterine myometrium (1), while primary intracranial angioleiomyoma is rare (2-4), since the first reported case by Lach et al. in 1994, only over 60 cases have been reported (6). Additionally, it appears to affect immunocompromised patients more frequently, such as those positive for Epstein-Barr virus infection (5), HIV infection (7), or receiving organ transplantation.

The pre-operative diagnosis of the lesion can be suggested by radiological features. However, it is sometimes misdiagnosed as meningioma, due to its homogeneously enhanced features after contrast brain MRI scan (Figure 2), as observed in our case, with the lesion located at the edge of right tentorium adjacent to brain stem (pontine) (Figure 2). Other tumors including lymphoma or metastatic tumors should be differentiated as well. In addition, the locations of intracranial angioleiomyoma are diverse. it can be found deep inside the tentorium, skull base (8-10), or cavernous sinus (11). Other sites include ventricular (1,3,12), and sellar region (13). Joo et al. reported an exceedingly rare case of epidural intracranial metastasis from angioleiomyoma (14). Howden et al. introduced a case of angioleiomyoma of the external auditory canal (15). We also retrospectively analyzed the location distribution from 68 surgical cases of intracranial angioleiomyoma at our center in the last 10 years (Table 1), among which, most cases were orbital angioleiomyomas, followed by skull base angioleiomyomas, including middle skull base, tentorium, cerebellopontine angle (CPA), and foramen magnum.

In this case, we used a very minimally invasive approach, sub-temporal craniotomy, for tumor resection, and the patient recovered quickly from the surgery without developing any new neurological deficits. Pathological examination confirmed the diagnosis of angioleiomyoma. Spindle shaped cells with blunt ends and few mitotic figures were found by H&E staining. Immunocytochemistry analysis revealed that the tumor cells were positive for CD34, SMA and vimentin, and focal positive for desmin (Figure 4), differentiating it from meningioma, schwannoma and solitary fibrous tumor. Histologically, angioleiomyoma is classified into three subtypes: solid-type, venous-type and cavernous type. Cavernous type tumor is composed of dilated vascular channels with proliferation of smooth muscle bundles in the intervascular spaces (Figure 4).

The standard therapy for primary intracranial angioleiomyoma remains to be gross total resection, and adjuvant radiation therapy for the residual tumor. Selbi et al. reported their experience using gamma knife radiation for the residual tumor six months after surgical resection (8), and they suggested that the vascular micro-structure inside the angioleiomyoma makes it very suitable for gamma knife therapy. Xiaofeng et al. reported treatment of the residual tumor with Cyber Knife following surgical debulking (11). In our patient, the tumor was totally resected, thus no additional therapy was needed. Six-months follow-up brain MRI showed no relapse of the tumor (Figure 3).

Conclusions

In summary, primary intracranial angioleiomyoma is rare, and is mostly discovered in immunocompromised patients. Here, we reported a case of intracranial angioleiomyoma mimicking meningioma in pre-operative radiological images, while post-operation pathology analysis confirmed the diagnosis of angioleiomyoma, with the presence of spindle shaped cells and few mitotic features. Currently, the optimal therapy strategy for primary intracranial angioleiomyoma remains to be surgical resection, and adjuvant radiation therapy for the residual tumor, such as gamma knife radiation or Cyber Knife. However, pre-operative diagnosis and differential diagnosis are important for surgical plan, and long-term follow-up of the lesion is advocated in case of recurrence or malignant transformation.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://tcr.amegroups.com/article/view/10.21037/tcr-24-151/rc

Peer Review File: Available at https://tcr.amegroups.com/article/view/10.21037/tcr-24-151/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tcr.amegroups.com/article/view/10.21037/tcr-24-151/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with Huashan Hospital Ethics Committee and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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