Brain Pathology Case of the Month - July 2011


Schwannoma grade I WHO of the jugular foramen associated with leptomeningeal blue nevus.


Phacomatosis pigmentovascularis (PPV) is described as a rare combination of a widespread vascular nevus (nevus flammeus - port-wine stain) with an extensive pigmentary nevus (nevus pigmentosus) (5, 6, 9). Happle (9) proposed a new classification of PPV into 4 types: I) phacomatosis cesioflammea, presenting one or more aberrant Mongolian spots and one or more port-wine stains; II) phacomatosis spilorosea which is characterized by presence of rosé-wine nevus; III) phacomatosis cesiomarmorata is characterized by a coexistence of aberrant Mongolian spots and cutis marmorata telangiectatica congenita; and IV) includes the unclassifiable types, like the presented case. Phacomatosis is the general term applied to describe some neurocutaneous syndromes (9). It is believed that approximately 50% of the patients affected of PPV have systemic involvement (6). Central nervous system defects, seizures, Sturge-Weber syndrome, hydrocephalus and even plexiforme neurofibroma are some of the neurological abnormalities reported in PPV (5, 6). However, the association of PPV with an intracranial tumor, especially a pigmented skull base tumor of the jugular foramen, has not been described to date.

The differential diagnosis of primary pigmented lesions of the leptomeninges includes primary malignant melanoma, melanotic schwannoma, meningeal melanocytoma, diffuse melanosis and cellular blue nevus. These lesions are believed to arise from the leptomeningeal melanocytes, which originate from the neural crest elements. Melanocytes are encountered in the basal layer of the epidermis and the leptomeninges covering the surface of the basal portions of the brain and brain stem. Therefore, pons, cerebellum, cerebral peduncles, medulla oblongata, interpeduncular fossa, inferior surface of the temporal, frontal and occipital lobes are the most common areas involved in the development of pigmented intracranial primary tumors (8, 13).

Melanomas are malignant lesions constituted of epithelioid cells with pleomorphic nuclei and large nucleoli. Melanotic schwannomas, on the other hand, comprise a rare variant of schwannomas composed of melanin-producing cells having the ultrastructural and immunophenotypical features of Schwann cells (16). Meningeal melanocytomas are typically well-differentiated lesions consisting of variable shaped cells arranged in tight nests, vasocentric fascicles, or sheet like arrangements of leptomeningeal melanocytes with variable melanin pigment (4, 15). Mitotic figures are absent or low in number, and either necrosis or hemorrhage usually are not documented (4, 15).

Diffuse melanosis is associated with congenital intradermal benign pigmented nevi in a rare nonfamilial disease called neurocutaneous melanosis (NCM). This condition encompasses benign as well as malignant melanocytic tumors of the central nervous system and large or multiple cutaneous melanocytic nevi (1, 13). To date, NCM has been classified as a phacomatosis caused by congenital dysplasia of the neuroectodermal melanocyte precursors resulting in excessive (focal or diffuse) proliferation of melanin-producing cells in the skin and leptomeninges (3, 13). Symptomatic NCM occurs in 7.5% of the patients suffering from large congenital melanocytic nevi (2).

Finally, blue nevus is a congenital benign melanocytic lesion which mostly occurs in the skin and eyelid (11). This tumor is classified as common or cellular blue nevus (CBN), which can rarely experience local aggressiveness and malignant transformation into melanoma, especially in scalp and periorbital regions (2, 10, 11). Moreover, some authors (2, 7, 8, 10, 11, 12, 13) reported contiguous intracranial invasion of the CBN which is very uncommon.

Interestingly, the bulk of the tumor in our case consisted of a schwannoma grade I WHO (Figures 7 and 8). The pigmented cells within the small fragments of tumor were attached to the schwannoma rather than part of it (Figures 7 and 8). The pigmented cells corresponded to melanocytes. Hence, the pigmented tumor is best described as a blue nevus-like tumor of the leptomeninges. This is not a melanotic schwannoma since typical melanotic schwannomas consist of spindle-shaped and epithelioid cells. In contrast, the tumor bulk in the presented case consisted of a typical schwannoma containing both Antoni A and Antoni B patterns.

Primary intracranial melanocytic tumors are occasionally associated with pigmented lesions of the skin (3). Blue nevus, nevus of Ota and NCM are skin lesions that have been described with concurrent intracranial malignant melanomas or meningeal melanocytomas (1, 3, 10, 11, 14). This case represents an extremely rare association of a skull base schwannoma together with a leptomeningeal blue nevus-like tumor in a patient affected by PPV and illustrates the importance of systemic examination in PPV.


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Contributed by Carlos H. Carvalho, MD, Leonardo M Batista, MD, DDS, Antje Bornemann, MD, PhD, Marcus André Acioly, MD. Marcos Tatagiba, MD, PhD

International Society of Neuropathology