Primary Spinal Cord Melanoma: A Two-Case Report and Literature Review

Here, we report two rare cases of primary spinal cord melanoma.

Case 1

A 38-year-old woman suffered from a burning sensation in the left trunk and leg and weakness of the left leg for more than 6 months. Magnetic resonance imaging (MRI) revealed three intradural masses at the C3, C7-T1, and T2 levels (Fig. 1). These three tumors showed hyperintense signal on T1-weighted imaging, a predominantly hypointense signal on T2-weighted imaging, and an enhancement on the contrast-enhanced T1-weighted images. Whole-body computed tomography (CT) and brain MRI showed no abnormal lesions at other sites in the body. The patient had a subcutaneous nodule on her back. The pathological diagnosis of the subcutaneous nodule was blue nevus without malignancy. Surgery was initially performed for the smallest tumor at the T2 level. In surgery, the gray dura mater was observed and the tumor showed black (Fig. 2-a, b). Total gross excision of the tumor was performed under an operative microscope (Fig. 2-c). The pathological diagnosis of the tumor was melanocytoma without malignancy. The patient underwent a total gross excision for two other intradural spinal cord tumors at the C3 and C7-T1 levels. The surgical findings were similar to those of the smallest tumor, but the pathological diagnoses of these two spinal cord tumors were malignant melanomas. After surgery, the patient's neurological symptoms improved and she underwent radiological therapy with local irradiation of 40 Gy in 16 fractions and chemical treatment with nivolumab. A brain MRI at 10 months after the surgery revealed the presence of metastatic lesions. Twenty months after surgery, the patient was alive and receiving palliative treatment.

Figure 1.

Magnetic resonance imaging of the cervical and thoracic spines demonstrating an intradural spinal cord tumor at the C3, C7-T1, and T2 levels.

The tumor shows hyperintense signal on T1-weighted images (a: sagittal, e: axial), predominantly hypointense signal on T2-weighted imaging (b, d), and enhancement on contrastenhanced T1weighted imaging (c).

Figure 2.

Intraoperative photos from the surgical microscope.

The gray dura mater is observed (a), and the black tumor is exposed after the dural incision (b). The tumor is completely removed (c).

Case 2

A 58-year-old woman suffered from numbness of the left leg for more than one year. MRI revealed an intramedullary lesion at the T10-11 level (Fig. 3). The tumor showed a hyperintense signal on T1-weighted imaging, a hypointense signal on T2-weighted imaging, and enhancement on contrast-enhanced T1-weighted images (Fig. 3). After opening of the dura mater during the surgery, the intramedullary dark black tumor was exposed from the spinal cord to the surface of the spinal cord (Fig. 4). The tumor was completely removed and the patient's symptoms were alleviated postoperatively. Although no other melanoma foci were found after dermatological examinations and positron emission tomography-CT, pathologic examination confirmed the diagnosis of primary malignant melanoma. After the surgery, the patient underwent radiological treatment at the resection site of the spinal cord tumor. She was able to walk without support at the 8-year follow-up without recurrence and metastasis of the tumor.

Figure 3.

Magnetic resonance imaging of the thoracic spine demonstrating an intradural spinal cord tumor at the T10-11 level.

The tumor shows hyperintense signal on T1-weighted images (a: sagittal, d: axial), hypointense signal on T2-weighted imaging (b), and enhancement on contrastenhanced T1weighted imaging (c).

Figure 4.

Intraoperative photos from the surgical microscope.

After the dural incision, the black tumor is exposed at the posterolateral to the spinal cord.

A melanoma is a malignant neoplasm of melanin-producing cells¹⁾. The incidence of primary spinal cord melanomas is rare. Primary malignant melanomas in the central nervous system have been reported to be only 1% of all melanomas and primary spinal cord melanoma is even rarer^2-4); thus far, primary spinal cord melanomas have been published only as case reports^2-6). The majority of malignant melanomas of the spinal cord show hyperintensity on T1-weighted imaging, hypointensity on T2-weighted imaging relative to the spinal cord signal, and homogeneous enhancement on contrast-enhanced T1-weighted images⁷⁾. The high signal intensity on T1-weighted imaging is a typical sign of a malignant melanoma of the spinal cord and is considered to be caused by the melanin pigmentation of the hemorrhagic foci⁷⁾.

The treatment of primary spinal cord melanoma is controversial and not yet standardized. Generally, surgical resection is recommended; however, total resection of a primary spinal cord melanoma is often difficult and some patients will require postoperative adjuvant treatment, such as radio and chemotherapy⁸⁾. Radiotherapy can be used as an effective adjuvant treatment for primary spinal cord melanoma⁹⁾. Although adjuvant radiation therapy has been used in some reports, the ideal target dose has not been established and it is unclear whether the irradiation should be performed locally or on the whole brain and spinal cord due to the lack of robust data⁸⁾. In our two cases, total resection of the spinal cord tumors was performed and the patients were treated with local irradiation. The optimal treatment for primary spinal cord melanoma should be determined depending on the patients conditions. After the surgery, positron emission tomography-CT and brain MRI as well as blood examination are useful tools for screening of metastasis of the primary malignant melanoma.

The prognosis for primary spinal cord melanoma is unpredictable due of the rarity of the tumor. The prognosis of patients with primary melanoma in the central nervous system has been shown to be superior to that of patients with metastatic lesions¹⁰⁾. It has been reported that the average survival period of patients with skin melanoma with metastases to the central nervous system is <1 year, and that the average life-span of patients with a primary central nervous system melanoma after treatment is 7 years¹¹⁾. For better prognosis of this tumor, early diagnosis and appropriate treatment is mandatory. The presence of primary spinal cord melanoma should be considered in the treatment of spinal cord tumors.

Conflicts of Interest: The authors declare that there are no relevant conflicts of interest.

Sources of Funding: There is no funding received for this work from any organizations and there is no support, including pharmaceutical and industry support.

Author Contributions: Toshio Nakamae wrote and prepared the manuscript, and all authors participated in the study design. All authors have read, reviewed, and approved the article.

Ethical Approval: Unnecessary

Informed Consent: Informed consent was obtained from the patients for publication of this case report and any accompanying images.