Malignant melanotic nerve sheath tumors or melanotic schwannomas or are an uncommon variant of schwannomas with malignant potential.
The age groups of peak incidence are slightly younger than that of conventional schwannomas, occurring most often in the third through fifth decades 1,5.
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 tumors 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 tumors 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
Complete resection is usually curative 3. Although generally indolent, approximately 10% of melanotic schwannomas are malignant 1,3. Metastatic disease occurs in a significant minority.
Consider lesions with subacute hemorrhage, such as cavernous malformation, that can account for T1 hyperintensity 5 .
- 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
- 5. Koeller KK, Shih RY. Intradural Extramedullary Spinal Neoplasms: Radiologic-Pathologic Correlation. (2019) Radiographics : a review publication of the Radiological Society of North America, Inc. 39 (2): 468-490. doi:10.1148/rg.2019180200 - Pubmed