[Differential diagnosis between melanotic schwannoma of gasserian ganglion and metastatic melanoma of middle cranial fossa].

ABSTRACT

We present a case of a rare tumor--melanotic schwannoma of trigeminal nerve root and gasserian ganglion. Differential diagnosis between metastatic melanoma and melanotic schwannoma (MS) is associated with serious difficulties and high responsibility. Metastatic melanoma is a high grade tumor while most MS are benign lesions with good outcome. By the date 105 cases of these tumors are described in the world literature, 3 of them originated from trigeminal nerve root and gasserian ganglion. MS predominantly occur in relatively young patients, they are characterized by presence of Carney's complex and psammomatous bodies and absence of primary focus. MS and metastatic melanoma have similar appearance on MRI due to presence of melanin granules. Indirect signs evident for MS include cystic structure and dumbbell-shaped growth. Metastatic melanoma of cranial nerves is more typical in people older than 40, primary focus in the face in the zone of innervation of affected nerve is common. In case of absence of the listed features differential diagnosis is based on immunohistochemical analysis and electron microscopy of tissue samples.