Melanocytoma of the foramen magnum

Abstract

This report concerns a 66-year-old man with a melanocytoma arising at the foramen magnum. Magnetic resonance imaging disclosed a well-circumscribed tumor extending from the medulla oblongata to C1 with gadolinium enhancement. A heavily pigmented tumor located under the leptomeninges was removed surgically. Although the patient died 8 months later of renal cell carcinoma, no recurrence or metastasis of the melanocytoma was detected by radiographic examination. Microscopically, the resected tumor was composed of polygonal to spindle-shaped cells containing large amounts of melanin. The bland nuclei of the tumor cells were of uniform size. No mitotic figures were seen. The tumor cells were positively immunostained for S-100 protein and by antibody HMB-45. They were not stained using the Ki-67 (MIB-1) antibody, indicating low proliferative activity. The ultrastructural examination revealed numerous mature melanosomes and basal laminae surrounding nests of cells. The tumor was diagnosed as a melanocytoma on the bases of its microscopic features and the lack of Ki-67 immunoreactivity. The ultrastructural and immunohistochemical features of melanocytomas are distinct from those of meningiomas. It is likely that melanocytomas and melanotic schwannomas represent opposite extremes of the continuous spectrum of neuroectodermal tumors derived from the neural crest.

Primary Cerebellopontine Angle Melanocytoma: Review

“…Although PCPAM and primary malignant melanomas of the leptomeninges originate from leptomeningeal melanocytes, they are different in appearance and behavior 14,15,16,17,18,19. PCPAMs have a much better prognosis than their malignant counterparts.…”

Meningeal melanocytoma of the planum sphenoidale

“…20 Our review of the literature revealed 35 cases of intracranial meningeal melanocytomas. [1][2][3][4][5][6][7][8][9][10][11][12][13][15][16][17][18][19][22][23][24][25][26][28][29][30][31][32][33] Of these 35 tumors, 18 were supratentorial and half of these occurred in Meckel cave ( Table 1). The locations of the other supratentorial melanocytomas also tended to be at or near the cranial base, including the sphenoid wing, 19 cavernous sinus, 7 temporal convexity, 23 occipital tentorial surface, 10,13 and frontal region.…”

“…27 Postoperative survival time in patients harboring intracranial meningeal melanocytomas has ranged from 1 to 28 years. [1][2][3][4][5][7][8][9][10][11][12][13]16,[18][19][22][23][24][25][26][28][29][30][31][32][33] …”

“…Most of the reported cases of meningeal melanocytomas have occurred either in the spinal canal or the posterior fossa. 3,5,8,9,12,15,18,[21][22][23][24][25][26]28,29,31,32 Although more rarely located supratentorially, a number of these tumors have been described in the Meckel cave. 1,2,4,16,25,30,33 We report the 19th case of a supratentorial meningeal melanocytoma and describe the first such tumor found to arise from the midline of the frontal base in the area of the planum sphenoidale.…”

June 2002: 57‐year‐old male with leptomeningeal and liver tumors

“…Meningeal melanocytomas occur at every age, are usually unilocular and appear as nodes attached to the dura mater. They are mainly located in the posterior cranial fossa or the spinal canal (4,11). Imaging studies of these tumors show homogeneous contrast enhancement (12).…”