Microsurgical resection of an intramedullary metastasis of rare histopathology—a case report and comprehensive literature review

Introduction

Intramedullary spinal cord metastases (ISCMs) are rare manifestations of systemic malignancies and represent 4–9% of central nervous system (1). Treatment decisions are largely based on expert opinion, as literature on ISCM microsurgery is limited to case reports and small series (1). Hence, chemo- and radiotherapy are typically preferred (1). However, an increase in published case reports and series of surgically treated ISCM has been observed, likely due to improved cancer therapies prolonging survival (2-12).

Under certain circumstances, such as rapid tumour progression, progressive neurological deterioration, unbearable neuropathic pain, or uncertainty of histopathological diagnosis, microsurgical resection of ISCMs should be considered (1). There are no guidelines or clinical consensus for the resection of ISCMs. To date, the management of these lesions remains highly controversial. Due to the limited prognosis of the disease, treatment focuses on keeping an acceptable functional status (13).

While intramedullary metastases of melanoma have been previously documented (14-18), our case presents a rare instance of amelanotic melanoma of unknown primary (MUP) discovered incidentally during surgery in a patient with known breast cancer. This highlights unique diagnostic and therapeutic challenges when managing patients with multiple malignancy histories. We present the following case in accordance with the CARE reporting checklist (available at https://jss.amegroups.com/article/view/10.21037/jss-24-115/rc).

Case presentation

History & presentation

A 59-year-old female patient was referred to our clinic for diagnosis and treatment of an unclear intramedullary lesion at the T10 level. She reported progressive, burning pain in the left groin area for 2 months, spreading to the ventral thigh and knee. Intermittently, the patient had noticed a sensory deficit around the left lateral thigh. The patient also noted gait unsteadiness and voiding difficulties. Her history included invasive breast carcinoma [stage pT2N1a; G2; L1, V0, Pn1, R1, with estrogen receptor (ER) 100%, progesterone receptor (PR) 60%, HER2 negative], treated with surgery, radiotherapy, and arimidex 2 years prior.

Neurological examination revealed gait ataxia and lower extremity hyperreflexia. The strength of all muscle groups of both lower extremities was unremarkable. Other than voiding difficulties, there were no obvious symptoms of conus or cauda dysfunction. Magnetic resonance imaging (MRI) revealed an intramedullary contrast-enhancing lesion at the T10 level with perifocal oedema, extending from C7 down to L1 (Figure 1). Tibialis somatosensory evoked potentials (SSEPs) were inconspicuous.

Figure 1 MRI scans showing a T10 intramedullary lesion with perifocal edema before surgery, and complete resection without recurrence after surgery. Preoperative MRI (upper row) shows the intramedullary lesion at T10 (7 mm × 6 mm × 10 mm) in axial (A) and mid-sagittal T1 with contrast (B). T2-weighted MRI (C) reveals perifocal edema. No other spinal mass was detected. Postoperative MRI at 14 months (lower row) shows no tumor recurrence in axial (D) or mid-sagittal T1 (E) and T2 (F). The spinal cord edema has completely regressed, though residual signal changes at T10 remain visible. MRI, magnetic resonance imaging.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committees and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for 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.

Preoperative workup

The differential diagnosis included ependymoma, astrocytoma or metastasis—likely secondary to the known breast carcinoma—given the extensive edema. An intramedullary abscess was less likely due to the absence of inflammatory markers and risk factors. The case was reviewed by our neuro-oncological tumor board, leading to further diagnostics, including full neuroaxis MRI, contrast-enhanced thoraco-abdominal computed tomography (CT), and lumbar puncture. Supplementary imaging showed no other tumorous lesions on either MRI or CT, and cerebrospinal fluid analysis was normal.

Given the unclear etiology and the patient’s worsening neurological deficits and pain, we opted for microsurgical resection to prevent further nerve damage and obtain a definitive diagnosis.

Surgery

In prone position with neuromonitoring leads placed, the T10–11 pedicles were localized via X-ray to plan the incision. After disinfection and sterile draping, a bilateral subperiosteal approach exposed the T10 lamina. Laminoplasty with bilateral cuts was performed using the bone tip of an ultrasonic surgical aspirator. Intraoperative ultrasound confirmed sufficient bony exposure and depicted the intramedullary lesion (Figure 2). D-wave electrodes were applied epidural, and baseline electrophysiological potentials were taken. The dura was opened and intradural exposure optimized by dural sutures. The optimal approach to the lesion was determined with ultrasound. After median spinal cord opening, this real-time navigation technique was used to safely reach the small intramedullary lesion. During the midline approach, we noticed a decrease in SSEPs of 70% on the left side and of 20–30% on the right side. The lesion appeared greyish, mottled and hypervascularized without a clear capsula. Samples were sent to pathology, resulting in internal debulking. Residual tumour portions were removed layer by layer with the micro-tip of the ultrasonic aspirator, until no residual visible tumour remained (Figure 2). Motor evoked potentials (MEPs) and D-wave monitoring remained stable throughout. No residual tumour was detected by ultrasonography. Dural closure was ascertained with 6.0 Prolene TF-1 suture and sealing matrix. The lamina was refixed with 4 two-hole titanium plates, and the wound was closed layer by layer in watertight fashion. The procedure lasted 160 minutes with 50 mL blood loss.

Figure 2 Intraoperative microscope images showing the resection cavity at T10. Both images (A,B) show residual marginal tumor tissue being removed. Ultrasound image before dura opening (C) reveals a hypoechogenic intramedullary mass in the spinal cord.

Postoperative course & outcome

Immediate postoperative examination revealed slightly reduced left leg strength at British Medical Research Council (BMRC) grade M4 and persistent left-sided paraesthesia, however with improved neuropathic pain. Otherwise, the patient was able to ambulate. Postoperative MRI studies showed no residual tumour, haemorrhage, or ischemia. The patient was discharged to neurological rehabilitation on the 7th postoperative day.

Histopathology and immunohistochemistry identified a metastasis of an amelanotic melanoma (Figure 3). A melanoma panel [NRAS p.Q61L (c.182A>T) SNV exon 3], thorough dermatologic and ophthalmologic exam (no primary lesion found), and positron emission tomography (PET)-CT were performed. PET-CT suggested a small right inguinal lymph node metastasis, resected 2 months later. Adjuvant radiation therapy (13×2.5 Gy) on the T9–11 levels and immunotherapy with nivolumab were administered.

Figure 3 Histological and immunohistochemical analysis showed a biphasic tumor with S100, SOX10, and vimentin positivity, and active mitoses. HE-staining (10×) of the resected tumor shows a cell-rich biphasic tumor with epithelioid and sarcomatoid parts (A). Immunohistochemical staining using polyclonal rabbit anti-S100 antibody demonstrates strong cytoplasmic and nuclear positivity (B). Immunohistochemical staining using monoclonal mouse anti-SOX10 antibody shows distinct nuclear positivity (C), and vimentin (not shown). (D) Multiple mitoses are visible (Ki67-staining, 10×). HE, haematoxylin and eosin.

Follow-up MRIs at 14 months showed no recurrent or residual tumor (Figure 1). The paraesthesia with radiation into the left lower extremity persisted. Therefore, pregabalin was applied for unpleasant—albeit not painful—sensation. The mild weakness of the left lower extremity recovered completely during follow-up. At currently 3 years postoperative, there is no sign of tumour recurrence, and the patient remains ambulatory, active and independent.

Discussion

The management of ISCM remains a controversial topic and is highly dependent on the patient’s goal of care and is consequently subject to a multi-disciplinary approach (1,12,13). Our case is even more peculiar and raises further questions regarding the treatment approaches since we report a case of a MUP with surgical resection, consequent work-up and surgical resection of inguinal lymph node metastasis. Considering the history of breast cancer in our patient and the fact that MUP had not been diagnosed prior to surgical resection, breast cancer metastasis was considered as differential diagnosis besides ependymoma, especially considering that breast cancer is the second most common primary site of intramedullary spinal metastases after lung cancer (19). Given the disabling condition of our patient, we decided to perform microsurgical resection of the lesion, even though there is no definitive evidence advocating for surgical resection (1,13). Consequently, surgical intervention resulted in immediate symptom relief in our patient but also in the detection of the melanotic malignancy and moreover the detection and resection of the lymph node metastasis. The absence of an identifiable primary tumor despite a thorough dermatologic and ophthalmologic examination, combined with the pattern of metastatic spread to both intramedullary and inguinal sites, suggests hematogenous spread from an occult primary. This pattern is consistent with the known behavior of MUP where the primary lesion may have regressed or remain microscopically undetectable (20-22). This approach concludingly contributed to disease-free survival at 3-year follow-up without any sign of recurrence.

Our case raises several relevant questions and highlights the need for a large, multi-center data collection and elaborate review and individual patient-data pooled analysis of the current literature. A central question is when surgical resection should be considered. This question, and which patient population benefits from resection of ISCM, cannot be adequately answered by the few case series with small numbers of cases or by the systematic reviews to date (1-3,6,12,23). In our specific case a conservative approach with chemotherapy and radiotherapy only would have led to missing the diagnosis of the melanotic malignancy and may have led to consequent deterioration of the patient’s condition. Microsurgical intervention should be considered more frequently given the advances in microsurgical techniques & intraoperative technologies that are nowadays commonly available and render resection safe, including intraoperative neuromonitoring, ultrasound and ultrasonic aspiration, etc. (24).

Moreover, our case raises awareness regarding potential additional malignancies in cases with a history of prior malignancies. This further highlights the relevance of a diligent work-up even though the patient’s history might suggest a plain explanation for the patient’s conditions. Whether microsurgical treatment of ISCMs improves or worsens the functional outcome and overall survival in patients is not known, as no prior case reports or series included a control group of non-surgically treated patients. Acting in the patient’s interest to improve and maintain the quality of life in—oftentimes palliative settings—is central and requires a multi-disciplinary approach (1,13,19).

Conclusions

We advocate for more evidence regarding the indication for surgical treatment of ISCMs. To achieve this, we highlight the need for a diligent work-up of the existing literature, as well as the conduction of large multi-center studies to be able to provide the best possible care for our patients.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-24-115/rc

Peer Review File: Available at https://jss.amegroups.com/article/view/10.21037/jss-24-115/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-24-115/coif). M.N.S. serves as an unpaid editorial board member of Journal of Spine Surgery from October 2023 to September 2025. A.V. discloses: royalties and consulting fees from Globus/NuVasive, OsteoCentric; royalties from ATEC; consulting fees from Surgical Theater, Medtronic, and Higgs Boson; serves on the Medical Advisory Board and supports attending meetings for StocDoc; and holds stock in Globus/NuVasive, Surgical Theater, OsteoCentric, ATEC, and Higgs Boson. The other 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 the ethical standards of the institutional and/or national research committees and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for 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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