Melanocitoma lombar: Apresentação de uma melanose neurocutânea

Background: Melanocyte lesions are diffuse or circumscribed tumours arising from the leptomeningeal dendritic melanocytes. In the nervous system they are found most frequently in the posterior fossa or along the spinal cord. The authors describe a case of neurocutaneous melanosis with leptomeningeal melanocytoma of the S1 root in which the symptoms and imaging aspects misleadingly suggested a diagnosis of schwannoma. Case Report: Forty-two years old man, with episodes of pain on the posterior face of the right thigh, associated with paresthesia, progressively worsening in three years. Then he began gait difficulty and priapism, constipation and urinary retention. On examination, he had saddle anaesthesia and abolished cremasteric reflex, without motor deficits. He had multiple congenital pigmented nevi spread over the trunk. MRI showed an expansive intra-dural lesion, posterior to L5 vertebral body, extending through the S1-S2 intervertebral foramen, in close proximity to S1 root. The tumour was isointense with focal hyperintensities on T2-weighted MRI, hyperintense on T1-weighted MRI and had gadolinium enhancement. Histopathological examination revealed a tumour invading dorsal ganglia and nerve roots. Tumoral cells were spindle-shaped. Their nuclei had prominent nucleoli and melanin rich cytoplasm. Immunohistochemistry was positive for the anti-melanosomal antibody HMB - 45, expressed S-100 protein and had a moderate nuclear proliferation index. There is no expression of GFAP, neurofilament proteins, cytokeratins and EMA. Based on the clinical, gross, and histological features, a final diagnosis of meningeal melanocytoma of the tumour was made. Considering the existence of multiple nevi a final diagnosis of neurocutaneous melanocytosis was made. Discussion: We found no other case report in the literature of lumbar meningeal melanocytoma in the setting of neurocutaneous melanosis. Meningeal melanocytomas are rare and their differential diagnosis must include malignant melanoma. Other central nervous system neoplasms of different histogenetic origin may undergo melanisation such as schwannoma, meningioma, medulloblastoma, paraganglioma and some gliomas. This distinction has determinant therapeutic and prognostic implications. Meningeal melanocytoma, although benign, can be locally very aggressive and has marked propensity to relapse. Complete tumoral resection is the best option. When it is not possible, post surgical irradiation is considered to be beneficial.