Neurol India Home 

Year : 2019  |  Volume : 67  |  Issue : 2  |  Page : 591--595

Conus melanocytoma: A rare spinal tumor

Vikas Sharma1, S Bhaskar1, Abhishek Kumar1, Minakshi Bhardwaj2,  
1 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research and Dr. Ram Manohar Lohia Hospital, New Delhi, India
2 Department of Pathology, Postgraduate Institute of Medical Education and Research and Dr. Ram Manohar Lohia Hospital, New Delhi, India

Correspondence Address:
Dr. Vikas Sharma
Department of Neurosurgery, PGIMER and Dr. Ram Manohar Lohia Hospital, New Delhi - 110 001

How to cite this article:
Sharma V, Bhaskar S, Kumar A, Bhardwaj M. Conus melanocytoma: A rare spinal tumor.Neurol India 2019;67:591-595

How to cite this URL:
Sharma V, Bhaskar S, Kumar A, Bhardwaj M. Conus melanocytoma: A rare spinal tumor. Neurol India [serial online] 2019 [cited 2020 May 28 ];67:591-595
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Melanocytoma is a rare tumor that arises from the leptomeninges, with an annual incidence of 1 per 10 million population. It accounts for less than 0.1% of all central nervous system (CNS) tumors.[1] The first description of this tumor was given by Limas and Tio in 1972.[2] It usually has an intracranial localization but may also involve the spinal column, where it is most often intradural and extramedullary. Intramedullary melanocytomas, such as the one we describe here, are extremely rare.

The histological differential diagnosis includes a melanotic schwannoma, malignant melanoma, melanotic meningioma, and melanocytosis. Intramedullary spinal melanocytoma is a rare entity. We present a case of a primary spinal melanocytoma in the conus region, and describe its symptoms, radiological features, histological findings, treatment, along with the current management options and literature review. Till now, 30 cases have been reported in the English literature. The details of the previously reported cases have been summarized in [Table 1].{Table 1}

A 26-year old female patient presented with a history of low-back pain for 3 years, radicular pain to the left buttock and posterior aspect of the left thigh for 2 years, and weakness in the left lower limb (LL) for 1 year. Systemic examination was within normal limits. There were no neurocutaneous markers. On motor system examination, bilateral upper limbs were normal, and there was hypertonia in both LLs with exaggerated knee and ankle reflexes and upgoing plantars. The power in the right and left LLs was 4+/5 and 3/5, respectively. The abdominal reflex was present in the upper quadrant and was absent in the lower quadrant. Sensory loss was present for all modalities in the left LL below the L3 dermatome. Bowel and bladder functions were normal.

CEMRI (contrast enhanced magnetic resonance imaging) of the dorso-lumbar spine showed a relatively well-defined soft tissue mass lesion of size 7.4 × 1.4 cm, involving the distal dorsal spine and conus medullaris at the level of T10–L1 vertebrae. It was iso- to hyperintense on T1-weighted (T1W) images and iso- to hypointense on T2W images with a mild heterogenous contrast enhancement. An area of cerebrospinal fluid (CSF) intensity was present proximal to the lesion that showed a mild peripheral enhancement. These findings were suggestive of an intramedullary lesion at the conus [Figure 1]. A T9–T12 laminotomy was done and a black-colored lesion arising from the conus, with the nerve roots of cauda equina entangled in it, was seen. The tumor was firm and was highly vascular. At some places, the tumor was adherent to the cauda equina nerve roots. Near-total excision of the tumor was done [Figure 2].{Figure 1}{Figure 2}

The macroscopic examination of the specimen was suggestive of a pigmented tumor. Histologic analysis revealed a highly cellular tumor comprising spindle to ovoid cells arranged in fascicles, sheets, and nests. Most of the cells were heavily pigmented with dark brown, coarse, granular pigment, obscuring the nuclear details. No mitosis was noted and occasional foci of necrosis were seen. Focal glial infiltration was noted [Figure 3], [Figure 4], [Figure 5]. Immunohistochemistry (IHC) analysis was positive for HMB-45 (human melanoma black-45) as well as S-100, and was negative for epithelial membrane antigen (EMA) and glial fibrillary acid protein (GFAP). The MIB-1 index was <1%. These features were suggestive of an intermediate grade melanocytoma.{Figure 3}{Figure 4}{Figure 5}

The patient had an increase in her paraparesis in the immediate postoperative period (right LL 2/5, left LL 0/5) with bladder involvement. She made a gradual recovery over 6 months. The patient received 50 Gy dose of radiotherapy in 25 fractions as an adjuvant therapy.

Postoperative MR imaging showed postoperative changes in the posterior elements from T9 to T10 levels. Hyperintensity in the dorsal cord and in the region of caudae quina at the region of T11 vertebra with a syrinx formation proximal to it were also seen. There was no evidence of enhancement seen in the operative bed [Figure 6].{Figure 6}

The patient's power improved to 4/5 in the right LL and between 0/5 to 2/5 in the left LL (hip movements 2/5, knee flexion 3/5, knee extension 0/5, ankle movements 0/5, and toe movements 2/5) at a 1-year follow-up. Her bowel and bladder functions remained normal. She had a persistent and minimal residual sensory impairment.

The leptomeningeal melanocytes are derived from the neural crest and are found in highest density underneath the medulla and along the cervical spinal cord.[10] Primary melanocytic neoplasms of the central nervous system (CNS) have been divided by World Health Organization into (1) diffuse melanocytosis and melanomatosis, (2) melanocytoma, and (3) malignant melanoma.[11] The age of the patients harboring these tumors lies in the fourth to fifth decade, with their incidence being more in female as compared to male patients.[12]

The gross appearance of a meningeal melanocytoma, as seen during surgery or at autopsy, is that of a well-encapsulated, nodular, dark brown or black lesion that is firmly attached to the underlying leptomeninges. These tumors have a positive immunohistochemical reaction to antimelanosomal antibody (HMB45), S-100 protein, and vimentin antibodies and a negative reaction to EMA, GFAP, cytokeratins.[13],[14] Primary melanomas have more Ki-67 labeling indices (an average of 8%) than melanocytomas (<1–2%).[15] The other differential diagnosis are melanocytic meningioma and melanocytic schwannoma [Table 2].[16]{Table 2}

On MR imaging, these tumors are isointense or hyperintense onT1W images and hypointense on T2W images and show a homogeneous enhancement on postcontrast images.[17]

The goal of treatment should be complete/gross total resection with preservation of neurological function. Radiotherapy is provided when resection is incomplete.[18] Local recurrences up to 12 years after surgery have been reported.[19] In case of local recurrence, resurgery can be attempted, provided the neurological function can be preserved. The other alternative is radiotherapy.

Rades and Schild[20] in their study concluded that complete tumor removal is superior to incomplete tumor removal with regard to local control and survival. In case of incomplete tumor removal, the outcome is improved by radiotherapy.

Gupta et al., have concluded that very little data is present regarding radiosurgery, and chemotherapy has no role.[13] The optimum treatment at present includes a safe surgical excision and adjuvant therapy. The high incidence of local recurrence in incompletely excised lesions mandates a long-term close follow-up.

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Conflicts of interest

There are no conflicts of interest.


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