DIAGNOSIS
Intradural Melanocytoma
DISCUSSION
Melanocytomas in the central nervous system are rare pigmented tumors that originate from leptomeninges. There have been 60 reported cases thus far in literature, of which about one third were found in spinal cord and remaining were intracranial mainly in the posterior fossa. The differential diagnosis of a solitary pigmented tumor in the spinal cord includes melanocytoma, pigmented schwannoma and malignant melanoma. Solitary melanocytic lesions in the central nervous system range from a histologically benign melanocytomas to highly aggressive malignant melanomas. Spinal melanocytomas mostly occur in the cervical or thoracic spine and usually present as intradural and extramedullary lesions on imaging. (1, 4, 6) Melanocytic neoplasms form a continuum from a well-differentiated melanocytoma to frankly malignant melanoma. Melanocytomas are discrete, non-infiltrative tumors composed of bland spindle or oval shaped cells with variable melanin content and without cytologic atypia or mitoses. However like other melanocytic tumors, they are immunoreactive to HBM-45 and S-100 protein but not to EMA (epithelial membrane antigen). (5) The classic electron microscopic features include presence of numerous melanosomes within spindle shaped cells. (1) This is particularly helpful in differentiating melanocytomas from melanotic schwannomas. Although melanocytoma is known as a benign tumor and the optimal treatment is complete resection (4), a close follow-up after surgical resection is necessary as recurrence remains an issue and it has been reported in the past. (2, 3)
REFERENCES
Contributed by Ali Mahta, MD, Ewa Borys, MD, Scott R. Vandenberg, MD, PhD, Bob Carter, MD, PhD, Santosh Kesari, MD, PhD