Melanotic schwannomas are uncommon, and more frequently aggressive, variants of schwannomas, usually encountered in somewhat younger individuals 1.
Melanotic schwannomas occur in two forms depending on the presence or absence of psammoma bodies:
- non-psammomatous melanotic schwannoma
- psammomatous melanotic schwannoma
Non-psammomatous melanotic schwannoma
Non-psammomatous melanotic schwannomas almost invariably affect the spinal nerves and paraspinal sympathetic ganglia 1,2.
Psammomatous melanotic schwannoma
Psammomatous melanotic schwannoma also arise from spinal nerves and paraspinal ganglia, but may also involve cranial nerves and visceral autonomic nerves 1.
Approximately half of individuals diagnosed with these tumours have underlying Carney complex 1-3.
Melanotic schwannomas appear as well circumscribed masses of variable pigmentation ranging from grey to black, depending on the amount of melanin 3.
Melanotic schwannomas are composed of Schwann cells which contain melanosomes 1,2. Psammomatous tumours also contain psammoma bodies 3.
The appearances of melanotic schwannomas are similar to conventional schwannomas except that they usually have intrinsic high T1 signal and T2 signal loss due to the presence of melanin 4.
Treatment and prognosis
Although generally indolent, approximately 10% of melanotic schwannomas are malignant 1,3. Complete resection is usually curative 3.
- 1. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK "WHO Classification of Tumours of the Central Nervous System. 4th Edition Revised" ISBN: 9789283244929
- 2. Merat R, Szalay-Quinodoz I, Laffitte E, Kaya G. Psammomatous Melanotic Schwannoma: A Challenging Histological Diagnosis. Dermatopathology (Basel, Switzerland). 2 (3): 67-70. doi:10.1159/000442708 - Pubmed
- 3. Shields LB, Glassman SD, Raque GH, Shields CB. Malignant psammomatous melanotic schwannoma of the spine: A component of Carney complex. Surgical neurology international. 2: 136. doi:10.4103/2152-7806.85609 - Pubmed
- 4. Hoover JM, Bledsoe JM, Giannini C, Krauss WE. Intramedullary melanotic schwannoma. Rare tumors. 4 (1): e3. doi:10.4081/rt.2012.e3 - Pubmed