An Uncommon Intramedullary Tumor: Primary Spinal Cord Melanoma

A 47-year-old woman was admitted with complaints of progressive weakness in the lower extremities and pain in the back and left leg. Thoracic magnetic resonance imaging (MRI) revealed a spinal intramedullary tumor between the T9 and L1 levels, which were iso- to hypointense on T2 and slightly hyperintense on T1-weighted images. The tumor was resected as total, and the diagnosis was malignant melanoma confirmed with histopathology. Neurological findings improved at the postoperative period and no residual or recurrence was noted on postoperative MRI at the 9-month follow-up. Primary melanoma of the spinal cord, particularly intramedullar localization, is seldomly reported in the literature. We report a primary malignant melanoma of the spinal cord and emphasize the diagnostic and prognostic challenges.

Keywords:Spinal cord neoplasms; Intramedullary; Malignant melanoma

IntroductionPrimary malignant melanoma of the central nervous system (CNS) accounts for only1% of all melanoma cases, although they are the third most common cause of CNS metastases [1]. Primary melanoma of the spinal cord is a rare entity. So far, only 40 cases were reported since the first case reported by Hirschberg in 1906. Therefore, the exact incidence is still unclear. We report a case of primary malignant melanoma of the spinal cord and emphasize the diagnostic and prognostic challenges in the light of the foregoing literature.

Case ReportA 47-year-old woman was admitted to our clinic with complaints of progressive worsening of severe back pain radiating to the left leg for over a course of six months. Weakness in the lower extremities, which began a few weeks ago, was another prominent complaint, and no remarkable finding was noted in her past medical history. Neurological examination revealed moderate paraparesis and numbness predominantly on the left lower extremity in which motor strength was assessed to be 3/5 in all the muscle groups, whereas the right lower extremity had 4/5 strength. Magnetic resonance imaging (MRI) of the thoracic spine showed an intramedullary spinal cord tumor between the T9 and L1 levels. The lesion was iso- to hypointense on T2 and slightly hyperintense on T1-weighted images. Diffuse contrast enhancement was also prominent on T1-weighted images after gadolinium injection (Fig. 1). The MRI images also showed a long segment of syrinx with multiple internal septa above the tumor from the T2 to T9 levels, and another syrinx cavity below the tumor at the levels of L1–L2. The preliminary diagnosis was ependymoma based on the MRI findings, where there were a well-circumscribed mass and a nonenhancing tumor with the associated rostral and caudal cyst. During the operation, laminectomies were performed from T9 to L1 levels. A dark gray vascular tumor was observed immediately after a dural incision (Fig. 2). This pigmented tumor showed clear pial invasion under the operative microscope. The tumor was hardly dissected from the spinal cord, particularly at the caudal pole. The tumor was excised grossly as total. Postoperative course was uneventful. Although she had no recovery in motor strength in the early postoperative period, motor findings and pain radiating from the back to the left lower extremity markedly improved one month after the operation. No residual or recurrence was noted on postoperative MRI at 9 months of follow-up. Histopathological sections demonstrated a highly cellular lesion composed of clusters of atypical cells with prominent nucleoli and marked eosinophilic cytoplasm. İmmunohistochemical staining revealed positive immunoreactivity for S100 protein and human melanoma black-45 (Fig. 3). The patient underwent a thorough systemic survey after confirmation of the diagnosis, including tumor markers, ophthalmological and dermatological examinations. Any other foci of melanoma could not be found and primary malignant melanoma was confirmed. The patient did not receive any radiotherapy or chemotherapy and was able to walk without support at the sixth-month follow-up.